WO2013060338A1 - Procédé de fermentation anaérobie et de production de biogaz - Google Patents

Procédé de fermentation anaérobie et de production de biogaz Download PDF

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WO2013060338A1
WO2013060338A1 PCT/DK2012/050397 DK2012050397W WO2013060338A1 WO 2013060338 A1 WO2013060338 A1 WO 2013060338A1 DK 2012050397 W DK2012050397 W DK 2012050397W WO 2013060338 A1 WO2013060338 A1 WO 2013060338A1
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organic
nitrogen
organic material
biogas
treatment
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PCT/DK2012/050397
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English (en)
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Frank Ulrik ROSAGER
Anders Peter JENSEN
Stefan Borre-Gude
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Xergi Nix Technology A/S
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Priority to EP12790786.3A priority Critical patent/EP2771474A1/fr
Publication of WO2013060338A1 publication Critical patent/WO2013060338A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M21/00—Bioreactors or fermenters specially adapted for specific uses
    • C12M21/04—Bioreactors or fermenters specially adapted for specific uses for producing gas, e.g. biogas
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M45/00—Means for pre-treatment of biological substances
    • C12M45/02—Means for pre-treatment of biological substances by mechanical forces; Stirring; Trituration; Comminuting
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M45/00—Means for pre-treatment of biological substances
    • C12M45/06—Means for pre-treatment of biological substances by chemical means or hydrolysis
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M45/00—Means for pre-treatment of biological substances
    • C12M45/09—Means for pre-treatment of biological substances by enzymatic treatment
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M45/00—Means for pre-treatment of biological substances
    • C12M45/20—Heating; Cooling
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P5/00—Preparation of hydrocarbons or halogenated hydrocarbons
    • C12P5/02—Preparation of hydrocarbons or halogenated hydrocarbons acyclic
    • C12P5/023—Methane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/582—Recycling of unreacted starting or intermediate materials

Definitions

  • the present invention facilitates efficient biomass processing and an increased production of renewable energy from processing and anaerobic fermentation of a wide variety of organic materials.
  • organic materials have a high energy potential which can be exploited by processing the organic material.
  • One form of processing an organic material is by performing an anaerobic fermentation resulting in the production of biogas. This process represents a conversion of an energy potential to a readily usable energy source.
  • Pre-treatment of biomasses - including lime pressure cooking - and partial stripping of ammonia N prior to performing a biogas fermentation is not always sufficient to preclude an undesirable inhibition of biogas producing bacteria by ammonia released from organic bound N not stripped during the pre-treatment step.
  • a plant for generating biogas from an anaerobic fermentation of processed organic material including solid and liquid parts.
  • the plant includes i) a lime pressure cooker for hydrolysing a first organic material comprising one or more sources of nitrogen; ii) an absorption unit for absorbing and
  • the method includes i) diverting a first organic material comprising one or more sources of nitrogen to a lime pressure cooker; ii) subjecting said first organic material to a lime pressure cooking step resulting in at least partly hydrolysing said first organic material comprising one or more sources of nitrogen, wherein said lime pressure cooking step results in the formation of ammonia fluids; iii) diverting said ammonia fluids formed in the lime pressure cooker to an absorption unit; iv) absorbing and condensing ammonia fluids diverted to the absorption unit from the lime pressure cooker; v) diverting lime pressure cooked organic material from said lime pressure cooker to a mixing tank; vi) mixing lime pressure cooked organic material with a further organic material in the mixing tank; vii) diverting the mixed, organic materials to one or more fermenters; viii) fermenting under anaerobic fermentation conditions said organic materials in said one or more fermenters, ix) generating biogas from said anaerobic fermentation of said organic materials; x) diverting said organic materials from said one or
  • Figure 1 illustrates a biogas plant where a lime pressure cooker is used to hydrolyze organic material prior to anaerobic fermentation and biogas production, according to an embodiment of the invention.
  • Figure 2 illustrates a pre-treatment system according to another embodiment of the invention.
  • FIG. 3 illustrates an energy system according to an embodiment of the invention.
  • Figure 4 illustrates a mode of operation of the biogas plant according to an embodiment of the invention.
  • Figure 5 illustrates a mode of operation of the biogas plant according to another embodiment of the invention.
  • Figure 6 illustrates a mode of operation of the biogas plant according to yet another embodiment of the invention.
  • Figure 7A-7C illustrates a biogas reactor fitted with a service facility allowing access to interior of the biogas reactor according to an embodiment of the invention.
  • Figure 8A illustrates methane yield from batch bottles with untreated Chicken Litter and Nix treated Chicken Litter with or without an extended thermal treatment at 70 °C according to an embodiment of the invention
  • Figure 8B illustrates which illustrates methane yield from batch bottles with untreated Chicken Litter and Nix treated Chicken Litter in the absence of saturated lime according to an embodiment of the invention
  • Figure 8C illustrates a graphical representation of TKN, TAN and Organic nitrogen (Org-N) levels in untreated and treated Chicken Litter according to an embodiment of the invention.
  • Figure 9A illustrates methane yield from batch bottles with untreated Cow Deep Litter and Nix treated Cow Deep Litter with or without an extended thermal treatment at 70 °C. Methane yields have been normalized according to an internal standard; Figure 9B illustrates effect of saturated lime in Nix treatment Cow Deep Litter and Nix treated in the absence of Ca(OH) 2 according to an embodiment of the invention, and Figure 9C illustrates a graphical representation of TKN, TAN and Organic nitrogen (Org-N) levels in untreated and treated Chicken Litter according to an embodiment of the invention.
  • Figure 10A illustrates methane yield from batch bottles with untreated and NiX treated pig fibres with or without an extended thermal treatment at 70 °C according to an embodiment of the invention
  • Figure 10B illustrates methane yield from batch bottles with untreated pig manure and Nix treated pig manure in the absence of saturated lime according to an embodiment of the invention
  • Figure 10C illustrates graphical representation of TKN, TAN and Organic nitrogen (Org-N) levels in untreated and treated pig fibres according to an embodiment of the invention.
  • Figure 1 1 A illustrates methane yield from batch bottles with treated and untreated AD fibre according to an embodiment of the invention
  • Figure 1 1 B illustrates a graphical representation of TKN, TAN and Organic nitrogen (Org-N) levels in untreated and treated AD fibre according to an embodiment of the invention
  • Figure 12A illustrates methane yield from batch bottles with treated and untreated hen litter according to an embodiment of the invention
  • Figure 12b illustrates a representation of TKN, TAN and Organic nitrogen (Org-N) levels in untreated and treated hen litter according to an embodiment of the invention.
  • Figure 13A illustrates a process configuration during thermophile operation without NiX treatment according to an embodiment of the invention
  • Figure 13B illustrates a process configuration during thermophile operation with NiX treatment according to an embodiment of the invention.
  • Figure 14 illustrates a process configuration during phase 2 - mesophile operation with recirculation and NiX treatment according to an embodiment of the invention.
  • Figure 15 illustrates effect of NiX treatment on NH 4 + -N concentration in the digester according to an embodiment of the invention.
  • Figure 16 illustrates removal of NH 4 + -N with NiX treatment vs. loss caused by high rate of pressure reduction according to an embodiment of the invention.
  • Figure 17 illustrates the nitrogen flow in the system is expressed in g of nitrogen per day according to an embodiment of the invention.
  • Figure 18 illustrates nitrogen flow around the NiX treatment unit (data are in g of nitrogen at a specific NiX treatment according to an embodiment of the invention.
  • FIG 19 illustrates Hydraulic Retention Time (HRT) and Solid Retention Time (SRT) according to an embodiment of the invention.
  • Figure 20 illustrates methane yield during phase 2 (mesophile operation) according to an embodiment of the invention.
  • Figure 21 illustrates feed flow rate, biogas yield (main vertical axis), NH 4 + -N concentration in the digester (secondary vertical axis) according to an embodiment of the invention.
  • Figure 22 illustrates Total Solids (TS) content of the digester and of the liquid after separation with centrifuge according to an embodiment of the invention.
  • Figure 23 illustrates the mass balance around the NiX treatment unit for a specific treatment according to an embodiment of the invention.
  • Figure 24 illustrates Nitrogen flow in the system where the data represents flow rates in g of nitrogen per day, according to an embodiment of the invention;
  • FIG 25 illustrates one embodiment of the processes and the plant for bioenergy generation according to the present invention.
  • Organic biomass and re-circulated liquid from the anaerobic digester (biogas fermenter(s)) are diverted to a lime pressure cooking step (NiX treatment) and lime (CaO / Ca(OH) 2 is added to create - at a temperature of more than 100°C and a pressure of more than 1 bar - a pH suitable for converting ammonium N (NH 4 + ) to gaseous ammonia (NH 3 ) - which can be stripped, collected e.g. in an ammonia scrubber, and converted into ammonium sulphate - which can subsequently be used as a fertilizer (cf. Figs.
  • the lime pressure cooked biomass is diverted to a buffer tank (as also illustrated in Figs. 1 and 2 (i.e. "dosing module") - prior to being diverted into one, or a series of at least two, connected anaerobe digesters for the production of biogas (cf. "primary digester” and “secondary digester” as illustrated in Fig. 4). Additional biomass may be mixed with the lime pressure cooked biomass in the buffer tank (as also illustrated in Figs. 1 and 4).
  • a conversion of organic nitrogen to ammonium N may take place in the buffer tank - and the generated ammonium N (NH 4 + ) may subsequently be converted to gaseous ammonia (NH 3 ) under suitable conditions.
  • a separation of fiber i.e. solid fraction, "spent biomass", also known as the digestate
  • liquid phase takes place and the liquid fraction is diverted (i.e. re-circulated) back to the lime pressure cooker, as also illustrated in Fig. 4.
  • Figure 26 illustrates a plant and a process as described above for Fig. 25 - with the addition that a pre-incubation step is being inserted prior to Nix treatment.
  • the biomass is being converted into more basic constituents, i.e. fx peptides, saccharides and fatty acids, chemically and/or biologically under anaerobic and/or aerobic conditions, and organic N - i.e. organic nitrogen bound in and forming part of the biomass, is subsequently released as or further converted into ammonium N (NH 4 + ) - which in turn - again under suitable conditions can be converted into gaseous ammonia (NH 3 ).
  • NH 4 + ammonium N
  • Figure 27 illustrates the addition of lime to the pre-incubation tank in order to increase the conversion of organic N to ammonium N (NH 4 + ) - and to shift the equilibrium between ammonium N (NH 4 + ) and gaseous ammonia (NH 3 ) in the direction of gaseous ammonia (NH 3 ) - with a view to stripping gaseous ammonia (NH 3 ) also during the pre-incubation. Additional like may be added during the lime pressure cooking step (not shown).
  • Figure 28 illustrates an embodiment in which ammonia is also stripped from the buffer tank following NiX treatment - in addition to being stripped during the lime pressure cooking step (i.e. nitrogen extraction - NiX treatment).
  • Figure 29 illustrates an embodiment in which gaseous ammonia (NH 3 ) is stripped from each and all of the pre-incubation tank, the lime pressure cooker (NiX treatment) and the buffer tank. It is illustrated that lime (CaO) is added to the pre-incubation tank, but additional lime may be added to the lime pressure cooker, if needed.
  • the operational conditions as well as the chemical reaction conditions are different for the pre-incubation tank and for the lime pressure cooker.
  • Figure 30 illustrates TAN generated during pre-incubation as function of %TS.
  • %TS varies from 15 % to 47% (hen manure).
  • Figure 31 illustrates the development of TAN and a comparison between water and AD liquid used as re-circulated suspension liquid for hen litter. Darker bars: TAN concentration at day 0; Lighter bars: TAN concentration after 17 days incubation according to an embodiment of the invention.
  • Figure 32 illustrates development of TAN for seven TS levels according to an embodiment of the invention.
  • TS 20%, oxygen level normal according to an embodiment of the invention.
  • Figure 34 illustrates effect of seeding on the mineralization process. TAN from the seeding material has been subtracted according to an embodiment of the invention.
  • Figure 35 illustrates content of uric acid bound nitrogen and protein bound nitrogen before and after mineralization according to an embodiment of the invention.
  • Figure 36A illustrates dry matter loss in hen litter during incubation
  • Figure 36B illustrates Total solids loss in hen litter during incubation according to an embodiment of the invention.
  • Figure 37 illustrates Net VFA production during incubation according to an embodiment of the invention.
  • Figure 38 illustrates specific methane production in the incubated samples according to an embodiment of the invention.
  • Figure 39 illustrates contribution of nitrogen mineralization to VS loss in hen litter under aerobic and anaerobic conditions according to an embodiment of the invention.
  • Figure 40A illustrates TS content of incubated samples
  • Figure 40B illustrates VS content of incubated samples, wherein darker bars represent Day 0 and lighter bars represent Day 22 according to an embodiment of the invention.
  • Figure 41 illustrates development of pH and TAN during incubation with chicken litter inoculated with pre-tank material (Figure 41 A), with AD liquid - 'neutral' (Figure 41 B), with AD liquid - alkaline (Figure 41 C), with AD liquid - acidic ( Figure 41 D), where cTAN data depicted on the right Y-axis and pH on the left Y-axis, according to an embodiment of the invention.
  • Figure 42 illustrates TAN, TKN and OrgN levels according to an embodiment of the invention, where Figure 42A illustrates TAN levels before and after incubation, where the increase after 22 days is shown above the lighter bar, Figure 42B illustrates TKN levels before and after incubation, where the decrease after 22 days is shows above the lighter bar, Figure 42C illustrates OrgN levels before and after incubation, where the decrease after 22 days is shown above the lighter bar, Figure 42D illustrates OrgN levels before and after incubation for chicken litter alone, where the decrease after 22 days is shown above the lighter bar, Figure 42E illustrates TAN levels before and after incubation for chicken alone, where the increase after 22 days is shown above the lighter bar.
  • Figure 43 illustrates uric acid levels before and after incubation, where the decrease after 22 days is shown above the lighter bar, according to an embodiment of the invention.
  • Figure 44 illustrates VFA levels according to an embodiment of the invention, where Figure 44A illustrates VFA levels in substrates, Figure 44B illustrates VFA levels in samples, Figure 44C illustrates change in VFAs during incubation as seen by subtracting substrate VFA levels from the sample VFA levels, and Figure 44D illustrates total VFA before and after incubation.
  • Figure 45 illustrates TAN in substrate materials according to an embodiment of the invention.
  • Figure 46 illustrates development of VFA levels in substrates from beginning to the end of the experiment included in Example 4 according to an embodiment of the invention.
  • Lime pressure cooking is an example of a pre-treatment processing step resulting in nitrogen extraction - a technical term often abbreviated "NiX" (cf. Figures 25 to 29).
  • Lime pressure cooking is in principle conducted at temperatures above 100°C and at a pressure of above 1 bar.
  • Lime pressure cooking results in the conversion of inorganic ammonia N (MH 4 + ) to gaseous ammonia (NH 3 ) as illustrated in Figures 25 to 29.
  • the term pre-treatment signifies that this processing step occurs prior to the step of anaerobic digestion and the production of biogas.
  • An additional pre-treatment processing step which occurs prior to the step of lime pressure cooking, is that of pre-incubation of the biomass to be lime pressure cooked and later subjected to anaerobic digestion.
  • the pre-incubation step also serves to improve biogas production by converting a biomass into smaller constituent parts by chemical hydrolysis, or by biological conversion, using one or more microbial populations and/or one or more enzymes.
  • the initial process of breaking down macromolecular structures of a substrate in an anaerobic fermentation involves a hydrolysis of macromolecular structures, such as proteins, carbohydrates and organic acids.
  • macromolecular structures such as proteins, carbohydrates and organic acids.
  • the constituent parts, or monomers, such as amino acid residues, sugars and fatty acids can be readily metabolized by microbial organisms.
  • hydrolysis of macromolecular components of organic materials represents an initial step in an anaerobic fermentation.
  • Anaerobic fermentations are sensitive to high levels of ammonia as the ammonia inhibits the bacteria which are responsible for the methanogenesis. Hence, when the bacteria are inhibited by high levels of ammonia, reduced amounts of biogas are being produced.
  • the pre-incubation steps of the methods of the present invention are aimed at increasing the removal of nitrogen sources from an organic biomass.
  • the pre-incubation step serves to effectively prevent ammonia inhibition during anaerobic fermentation and biogas production.
  • Nitrogen can be present in an organic biomass either as organic nitrogen - fx nitrogen present in proteins and organic acids - or as inorganic nitrogen - in the form of ammonium.
  • organic bound nitrogen will have to initially be converted into inorganic ammonium, which is then stripped in the form gaseous ammonia. This is performed under suitable conditions - primarily involving a high pH and an increased temperature.
  • the ammonium available for stripping in the lime pressure cooker is determined by the amount of inorganic nitrogen which is entered into the lime pressure cooker for ammonia stripping.
  • a further pre-treatment step in the form of a pre-incubation of an organic biomass is introduced.
  • the pre-incubation step comprises one or both of a pre- fermentation step and/or a chemical hydrolysis step. Pre-fermentation can result in a hydrolysis and/or further break-down of e.g. proteins, carbohydrates and other
  • the pre-incubation step comprises a microbial fermentation resulting in the decomposition of organic macromolecules present in the organic material which is to be subsequently subjected to anaerobic fermentation and biogas fermentation.
  • the microbial fermentation and/or hydrolysis of macromolecules present in an organic material which takes place during the pre-incubation step will thus contribute to an increased N- mineralization process during pre-incubation.
  • the conversion of organic N to inorganic N which takes place at the pre-incubation step is at least facilitated by biological and enzymatic processes catalyzed by microbial organisms present in the biomass comprising the organic bound N.
  • enzymes synthesized by microbial organisms residing in the organic material to be processed are largely responsible for the conversion of organic N to inorganic N during pre-incubation - and such enzymes will not be allowed to exert their action during a lime pressure cooking step - which is a thermo-chemical process.
  • the methods of the present invention can be characterized as a two-step fermentation method in which the individual steps are separated by a thermo-chemical processing step - i.e. lime pressure cooking - performed at an elevated temperature and pressure, and under alkaline pH conditions.
  • a thermo-chemical processing step i.e. lime pressure cooking - performed at an elevated temperature and pressure, and under alkaline pH conditions.
  • the first fermentation step - preceding the thermo-chemical processing step - is a facultative anaerobic fermentation reaction during which, in one embodiment of the present invention, essentially no biogas is produced - as the organic material can be expected to undergo initial fermentation stages during the first fermentation step, but not, or only to a limited extent, methanogenesis.
  • Methanogenesis constitutes one of the latter stages of an anaerobic fermentation - i.e. a stage which is reached only after prior stages, such as e.g. acidogenesis and acetogenesis.
  • the second fermentation step which takes place after the thermo-chemical processing step - is a strictly anaerobic methanogenesis. Accordingly, the second fermentation step is aimed at producing biogas by using the pre-fermented and thermo-chemically treated organic material as a substrate.
  • a dual fermentation method for generating biogas from anaerobic fermentation of processed organic material comprising solid and liquid parts, said method comprising the steps of i) subjecting an organic material comprising one or more sources of nitrogen to a facultative anaerobic fermentation resulting in at least partial hydrolysis of the organic material and at least partial conversion of organic N (nitrogen) present in the organic material to inorganic N, and wherein essentially no biogas is produced; ii) subjecting the organic material fermented in step i) to lime pressure cooking, wherein the lime-pressure cooking results in a further hydrolysis of said organic material, and wherein said lime pressure cooking step results in the conversion of inorganic N to ammonia fluids; iii) subjecting the organic material fermented in step i) and subjected to lime
  • step ii) pressure cooking in step ii) to a strictly anaerobic fermentation resulting in the production of biogas.
  • the first microbial fermentation reaction results in a conversion of organic bound N to inorganic N - an increased amount of biogas can be produced in the second microbial fermentation reaction (i.e. the methanogenesis) - as more inorganic N enters the lime pressure cooking step - where the inorganic N is converted to gaseous ammonia which is stripped.
  • the methanogenesis i.e. the methanogenesis
  • the facultative anaerobic bacteria according to the methods of the present invention have a temperature optimum in the range of from approx. 30°C to 37°C. Accordingly, the bacteria can be termed "mesophilic" because of this temperature optimum.
  • seeding of the pre-incubation is important for the pre- fermentation which takes place - and approx. 10 to 20 % (w/w) of the contents of a pre- fermentation tank is preferably retained and re-circularized to the next batch pre-fermentation. Accordingly, several interconnected pre-fermenters can be present - so that one can seed approx. 10 to 20 % (w/w) of the contents of one pre-fermenter into a connected pre-fermenter.
  • any suitable number such as fx 2, 3, 4, 5 or 6 interconnected pre-fermentation tanks can be operated as individual, but connected pre-fermentation "batch" fermentations at different stages of the pre-fermentation can be present.
  • Each "batch" pre-fermenter is connected to the lime-pressure cooker and pre-fermented biomass can be diverted from any pre-fermenter to the lime pressure cooker. In this way, one will be able to operate the methods of the present invention as a continuous fermentation process for pre-fermentation and biogas production.
  • the maximum TS (total dry matter) content of the biomass subjected to pre-fermentation is preferably approx. 30%, such as at the most 25 % (w/w).
  • the pH optimum for the pre-fermentation is broad and ranges from a pH value of approx. 6,5 to a pH value of approx. 8,5. pH values following a pre-fermentation are preferably in the range of from approx. 6,0 to approx. 7,5.
  • the duration of the pre-fermentation will depend on the reaction conditions, including temperature, pH, total dry matter content, and the like. It is preferred that the pre-fermentation is at the most approx. 96 hours, such as at the most 72 hours, for example at the most 60 hours, such as at the most 50 hours, for example 40 hours. However, both longer and shorter durations can be employed. It is possible to obtain, following a pre-fermentation step according to the present invention, a conversion of organic bound N to inorganic N of up to 70 to 80 %. However, depending on the reaction conditions and the content of organic N, lower values can also be obtained - such as for example conversion rates of approx. 35%, approx. 40%, approx. 45%, approx. 50%, approx. 55%, approx. 60%, and approx. 65%. This will also depend on the reaction conditions employed for the pre-fermentation.
  • At least 80%, such as at least 85%, for example at least 90%, such as at least 95% or more of all nitrogen containing organic acids, such as e.g. uric acid, are converted to ammonia N during a pre-fermentation step operated under the conditions disclosed e.g. herein above.
  • a minimum of 30% such as a minimum of 40%, for example a minimum of 50%, such as a minimum of 60% of the organic bound nitrogen originating from protein is converted into inorganic N during a pre-fermentation.
  • the anaerobic fermentation can in principle be conducted either i) as a pre-incubation step, prior to a nitrogen extraction step, and/or ii) in the form of an anaerobic fermentation and biogas production (methanogenesis, cf. above) conducted following a nitrogen extraction step.
  • This is illustrated in figures 26 to 29.
  • Acetate and hydrogen produced in the first stages of an anaerobic fermentation can be used directly by methanogens.
  • Other molecules such as volatile fatty acids (VFAs) with a chain length that is greater than that of acetate, must first be catabolised into compounds that can be directly metabolised by methanogens.
  • VFAs volatile fatty acids
  • the biological process of acidogenesis is one wherein there is further breakdown of the remaining components by acidogenic (fermentative) bacteria.
  • VFAs are created along with ammonia, carbon dioxide, and hydrogen sulphide, as well as other by-products.
  • the third stage of an anaerobic fermentation is acetogenesis.
  • simple molecules created through the acidogenesis phase are further digested by acetogens to produce largely acetic acid as well as carbon dioxide and hydrogen.
  • the final stage of an anaerobic fermentation is that of methanogenesis.
  • Methanogens metabolise intermediate compounds formed during the preceding stages of the anaerobic fermentation, and these compounds are metabolised into methane, carbon dioxide, and water.
  • the afore-mentioned compounds are the major constituents of a biogas.
  • Methanogenesis is sensitive to both high and low pHs - and methanogenesis generally occurs between pH 6.5 and pH 8. Remaining, non-digestible organic material that the microbes present in the biogas fermenter cannot metabolise, along with any dead bacterial remains, constitutes what is termed the digestate from the fermentation.
  • organic materials Apart from having a high energy potential, many organic materials also have a high content of nitrogen (N) - in the form of inorganic N (calculated as TAN - total amount of N (NH 3 and NH 4 + )) and organic N e.g. present in proteins, uric acid and other organic sources of N.
  • N nitrogen
  • TAN total amount of N
  • organic N e.g. present in proteins, uric acid and other organic sources of N.
  • organic materials When such organic materials are used as substrates for converting organic materials into bio energy in a bio energy plant, in particular biogas in a biogas plant, organic N and / or protein will gradually be converted to ammonia e.g. during an anaerobic fermentation resulting in the production of biogas.
  • ammonia in a bio energy plant - especially at high levels - represents a problem as many biogas producing bacteria are sensitive to high levels of ammonia - and high ammonia levels in a biogas fermenter will thus reduce or inhibit the production of methane.
  • the formation of high levels of ammonia i.e. above a certain threshold level, cf. below, will kill biogas producing bacteria and inhibit any further biogas formation.
  • the inhibitory levels of ammonia in a biogas fermenter depend on the conditions used. Under thermophilic fermentation conditions, approx. 3,0 to 4,2 kg ammonia per ton of biomass is considered inhibitory, while under mesophilic fermentation conditions the figure is approx. 5,0 to 7,0 kg ammonia per ton of biomass - depending of the pH value in the digester.
  • the biogas generating fermentation process can be expected to be completely inhibited at ammonia levels of approx. 7,0 kg to 7,5 kg ammonia per ton of biomass.
  • ammonia (NH 3 ) which is inhibitory to the biogas production.
  • the equilibrium between ammonia and ammonium (NH 4 + ) salts will depend on e.g. pH and temperature. The higher the pH and the higher the temperature, the more the equilibrium is shifted towards the ammonia.
  • Stripping of ammonia will result in a decreased pH value in the fermenter and it is preferred that the pH value of an anaerobic biogas fermentation shall be below a pH value of approx. 8,5.
  • ammonia inhibition threshold values are generally taken into consideration when operating commercial biogas plants using conventional organic materials as substrates for the biogas producing bacteria. Many such plants are operated according to a two step strategy initially adopting thermophile digestion conditions in a first fermentation step and mesophile digestion conditions in a separate and subsequent, second fermentation step.
  • the conversion of organic N to ammonia N progresses during an anaerobic fermentation process - i.e. during the process of generating biogas by anaerobic fermentation - and a conversion of as much as approx. 50 % to 70 % of organic N to ammonia N can be expected in accordance with the present invention.
  • the anaerobic fermentation resulting in the production of biogas may be preceded by one or more initial processing steps aimed at stripping ammonia N from the organic material prior to the biogas production.
  • One such initial processing step is a pre-incubation step - performed prior to lime pressure cooking - wherein organic N forming part of the biomass to be processed is converted to inorganic N by chemical hydrolysis or by microbial action.
  • the pre-incubation step takes place in a preincubation tank, as illustrated e.g. in Figs. 26 to 29.
  • Another initial processing step is that of lime pressure cooking - a step which subjects the optionally pre-incubated organic material, cf. herein above, to an initial hydrolysis under alkaline conditions at an elevated pressure - i.e. more than 1 bar - and at a temperature of more than 100°C.
  • yet another pre-treatment step may be used for increasing the conversion of organic bound N in an organic biomass.
  • the lime pressure cooked organic material can be diverted to a buffer tank and the retention time in this buffer tank determines the result of this pre-treatment step.
  • the pH is adjusted to a pH value of less than 8,5, such as less than 8,0, for example less than 7,0, and preferably not less than 6,0.
  • a further conversion of organic bound N in an organic biomass can be allowed to occur in the buffer tank and - optionally - ammonia can also be stripped from the buffer tank.
  • Ammonia N stripped from the organic material e.g. under a lime pressure cooking step - and/or during pre-incubation, and/or during buffer tank treatment - can initially be diverted to a stripper and sanitation tank - or alternatively diverted directly to an absorption column for absorption of the stripped ammonia N.
  • the stripper and sanitation tank will also be connected to an absorption column for absorption of the stripped ammonia N.
  • no organic bound N is converted to ammonia during the lime pressure cooking step.
  • organic bound N is converted to ammonia both during the pre-incubation step and during the subsequent anaerobic fermentation resulting in the production of biogas - as illustrated e.g. in Figs. 26 to 29.
  • Ammonia N stripped from the organic material prior to, during, or after the lime pressure cooking step can be diverted to a stripper and sanitation tank for further incubation under conditions resulting in further conversion of organic N to inorganic N - or, alternatively, diverted directly to an absorption column for absorption of the stripped ammonia N.
  • the absorption column can also be connected to the stripper and sanitation tank so that any ammonia N stripped from the stripper tank can be diverted to the absorption column.
  • the lime pressure cooked and, at least partly, ammonia N stripped organic material is
  • the lime pressure cooked organic material is initially diverted to a mixing tank prior to being diverted to the biogas fermenter.
  • Mixing of lime pressure cooked material with further organic materials, for which there is no need for performing a lime pressure cooking step, can take place in a mixing tank prior to diverting the mixture to the biogas fermenter for anaerobic fermentation.
  • anaerobically fermented organic material is separated into a solid and a liquid fraction.
  • the liquid fraction comprising ammonia N is diverted, or re-cycled, to the lime pressure cooker for stripping of ammonia.
  • Ca(OH) 2 or CaO can be used to increase the pH in a lime pressure cooking step.
  • Lime is used on an industrial scale by for instance the cement industry and is therefore cheap and readily available as a bulk ware.
  • Other bases may also be employed, such as e.g. NaOH or KOH.
  • stripped ammonia When the stripped ammonia is absorbed and an ammonia concentrate is produced, one can divert stripped ammonia to e.g. sulphuric acid present in an absorption column.
  • Sulphuric acid is an industrial bulk ware and it is available in a technical quality appropriate for use in
  • absorption columns stripping ammonia from slurry and other waste waters (e.g. Sacuk et al. 1994).
  • Thermal and chemical hydrolysis of a biomass represents one way to increase the availability of organic material for biogas generation.
  • Complex carbohydrates such as e.g. cellulose, hemicelluloses and lignin, are not completely hydrolysed by such treatments.
  • fibres from straw, maize and other crops are not made available as suitable substrates for methane formation by such treatments (Bjerre et al 1996; Schmidt and Thomsen 1998; Thomsen and Schmidt 1999; Sirohi and Rai 1998).
  • the present invention concerns methods for performing an anaerobic digestion of a biomass, such as e.g. organic materials comprising one or more of animal manures, energy crops, category 2 waste materials, and similar biomaterials.
  • a biomass such as e.g. organic materials comprising one or more of animal manures, energy crops, category 2 waste materials, and similar biomaterials.
  • biomasses capable of being used as an "input biomass” and subsequently processed in accordance with the methods of the present invention are disclosed herein below in more detail.
  • the biomasses can comprise e.g. solid manure waste products from e.g. animal farms, poultry farms, dairies, slaughterhouses, marine fish farms, fish and meat industries as wells as energy crops and or other plants.
  • the input biomass or feedstock can also comprise liquid manure, dry litter, such as cattle, poultry, offal from cattle, poultry, mink, vegetable oil and glycerin, sludge, whey and the like, corn silage, fish category 2 waste, and industrial waste, including category 3 waste materials.
  • Biomass can also be any material that comes from plants. Some plants, like sugar cane and sugar beets, store the energy as simple sugars. These are mostly used for food. Other plants store the energy as more complex sugars, called starches. These plants include grains like corn and are also used for food.
  • cellulosic biomass Another type of plant matter, called cellulosic biomass, is made up of very complex sugar polymers, and is not generally used as a food source. This type of biomass is under consideration as a feedstock for bioethanol production. Specific feed stocks under
  • Cellulose is the most common form of carbon in biomass, accounting for 40%-60% by weight of the biomass, depending on the biomass source. It is a complex sugar polymer, or polysaccharide, made from the six-carbon sugar, glucose. Its crystalline structure makes it resistant to hydrolysis, the chemical reaction that releases simple, fermentable sugars from a polysaccharide.
  • Hemicellulose is also a major source of carbon in biomass, at levels of between 20% and 40% by weight. It is a complex polysaccharide made from a variety of five- and six-carbon sugars. It is relatively easy to hydrolyze into simple sugars but the sugars are difficult to ferment to ethanol.
  • Lignin is a complex polymer, which provides structural integrity in plants. It makes up 10% to 24% by weight of biomass. It remains as residual material after the sugars in the biomass have been converted to ethanol. It contains a lot of energy and can be burned to produce steam and electricity for the biomass-to-ethanol process.
  • the percentages cited herein below are weight percentages - i.e. (weight / weight), or (mass / mass).
  • the input biomass has in one aspect of the present invention a carbon content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • the input biomass has in one aspect of the present invention a protein content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • 5% to 90% by weight such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55%
  • the input biomass has in one aspect of the present invention a fat or lipid content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • 5% to 90% by weight such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as
  • the input biomass has in one aspect of the present invention a nitrogen or ammonia content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • 5% to 90% by weight such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such
  • the input biomass has in one aspect of the present invention a fiber content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • 5% to 90% by weight such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55%
  • the input biomass has in one aspect of the present invention a sugar content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • 5% to 90% by weight such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55%
  • the input biomass has in one aspect of the present invention a polysaccharide content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • a polysaccharide content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to
  • the input biomass has in one aspect of the present invention a monosaccharide content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • a monosaccharide content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to
  • the input biomass has in one aspect of the present invention a lignin content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • a lignin content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%,
  • the input biomass has in one aspect of the present invention a hemicellulose content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • a hemicellulose content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%,
  • the input biomass has in one aspect of the present invention a starch content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • a starch content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50%
  • the input biomass has in one aspect of the present invention a sugar polymer content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • 5% to 90% by weight such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from
  • the input biomass has in one aspect of the present invention a cellulose content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50% to 55%, such as from 55% to 60%, for example from 60% to 65%, such as from 65% to 70%, for example from 70% to 75%, such as from 75% to 80%, for example from 80% to 85%, such as from 85% to 90% or any combination of these intervals.
  • a cellulose content of from 5% to 90% by weight, such as from 5% to 10%, for example from 10% to 15%, such as from 15% to 20%, for example from 20% to 25%, such as from 25% to 30%, for example from 30% to 35%, such as from 35% to 40%, for example from 40% to 45%, such as from 45% to 50%, for example from 50%
  • the input biomass has in one aspect of the present invention a pH between 0 and 14, such as from 0 to 1 , for example from 1 to 2, such as from 2 to 3, for example from 3 to 4, such as from 4 to 5, for example from 5 to 6, such as from 6 to 7, for example from 7 to 8, such as from 8 to 9, for example from 9 to 10, such as from 10 to 1 1 , for example from 1 1 to 12, such as from 12 to 13, for example from 13 to 14, or any combination of these intervals.
  • the methods of the present invention are capable of producing increased amounts of renewable energy while at the same time refining several nutrients comprised in the digested biomass to fertilizers of commercial quality.
  • ammonia stripping results in lowering of the ammonia concentration by more than 10%, such by more than 20%, such as by more than 30%, such as by more than 40%, such as by more than 50%, such as by more than 60%, such as by more than 70%, such as by more than 80%, such as by more than 90%, such as by more than 95% or such as more than 99%.
  • the level of ammonia and/or nitrogen can be measured before and after the ammonia stripping step and the lowering of the ammonia concentration can be determined.
  • the ammonia stripping can result in an ammonium concentration of less than 50 g dm “3 , such as less than 40 g dm “3 , such as less than 30 g dm “3 , such as less than 20 g dm “3 , such as less than 15 g dm “3 ,such as less than 10 g dm “3 ,such as less than 8 g dm “3 , such as less than 6 g dm “3 , such as less than 2 g dm “3 , such as less than 1 g dm "3 , such as less than 0.5 g dm "3 ,or such as less than 0.1 g dm “3 .
  • Anaerobic digestion as used herein shall denote any breakdown of organic matter by bacteria in the absence of oxygen.
  • the terms anaerobic digestion and anaerobic fermentation are used interchangeably herein.
  • a method for generating biogas from an anaerobic fermentation of processed organic material comprising solid and liquid parts, said method comprising the steps of i) diverting a first organic material comprising one or more sources of nitrogen to a lime pressure cooker; ii) subjecting said first organic material to a lime pressure cooking step resulting in at least partly hydrolysing said first organic material comprising one or more sources of nitrogen, wherein said lime pressure cooking step results in the formation of ammonia fluids; iii) diverting said ammonia fluids formed in the lime pressure cooker to an
  • absorption unit iv) absorbing and condensing ammonia fluids diverted to the absorption unit from the lime pressure cooker; v) diverting lime pressure cooked organic material from said lime pressure cooker to a mixing tank; vi) mixing lime pressure cooked organic material with a further organic material in the mixing tank; vii) diverting the mixed, organic materials to one or more fermenters; viii) fermenting under anaerobic fermentation conditions said organic materials in said one or more fermenters, ix) generating biogas from said anaerobic fermentation of said organic materials; x) diverting said organic materials from said one or more fermenters to a
  • the one or more sources of nitrogen in the liquid fraction preferably comprise inorganic nitrogen sources, such as ammonium salts.
  • Solid organic material is preferably diverted to the lime pressure cooker from a reception station suitable for receiving solid organic material
  • liquid organic material is preferably diverted to the lime pressure cooker from a reception tank suitable for receiving liquid organic material.
  • Lime is preferably diverted to the lime pressure cooker from a lime storage tank suitable for diverting lime directly to the lime pressure cooker.
  • Solid and/or liquid organic materials for which there is no need for lime pressure cooking can be diverted directly to the mixing tank and mixed with lime pressure cooked organic material in the mixing tank. It is possible in one embodiment to divert ammonia fluids from the mixing tank to the absorption unit, prior to diverting said mixed organic materials stripped of ammonia from the mixing tank to one or more fermenters suitable for the production of biogas.
  • the mixed organic materials are preferably fermented initially in a first fermenter under a first set of fermentation conditions, and subsequently diverted to a second or further fermenter and fermented under a second or further set of fermentation conditions.
  • the organic materials are initially fermented under thermophile fermentation conditions and subsequently, in a separate fermentation step, the organic materials are fermented under mesophilic fermentation conditions.
  • the biogas produced by thermophilic and/or mesophilic fermentation is preferably diverted to a gas storage facility operably connected to the one or more fermenters.
  • Biogas as used herein denotes a renewable, gaseous fuel derived from biological materials that can be used as an energy source instead of fossil fuels, typically to replace conventional natural gas, propane, heating fuel oil, diesel fuel, or gasoline.
  • Raw biogas is composed of a mixture of combustible gases (principally methane, but also including hydrogen and light hydrocarbons, such as e.g. carbon monoxide, ethane, etc.), and various inert gases and impurities, such as carbon dioxide and hydrogen sulfide.
  • Methane is a combustible gas with the chemical formula CH 4 that can come from fossil or renewable processes.
  • the present invention can be used for producing increased amounts of biogas from a wide range of organic substrates, including all types of animal manures, energy crops, crops residues and other organic waste materials, including category 2 waste materials.
  • the present invention is also directed to an optimized waste-to-energy process based on bio- gasification using anaerobic digestion and wet fermentation for increasing the yield of energy obtained e.g. per ton of biomass.
  • the above-cited method can include a subsequent slurry separation step, i.e. one or more steps resulting in the refinement of selected nutrients, such as phosphor (P) and/or potassium (K) contained in e.g. animal manures.
  • the invention may be applied to separate the main nutrients nitrogen (N) and/or phosphorus (P) from animal manures and refine the nutrients to fertilizer products of commercial quality.
  • the organic material to be pre-incubated and/or lime pressure cooked can comprise a maximum of 50% solid parts, such as a maximum of 40% solid parts, for example a maximum of 30% solid parts, such as a maximum of 20% solid parts.
  • the organic material may be in the form of a liquid fraction comprising a maximum of 10% solid parts, or the organic material to be pre-incubated or lime pressure cooked may be mixed with such a liquid fraction.
  • the lime pressure cooking of the organic material can be performed at a temperature of from more than l OCO to preferably less than 250 °C, at a pressure of from preferably 2 to preferably less than 20 bar, and with an addition of lime sufficient to reach a pH value of from about 9 to preferably less than 12, and with an operation time of from at least 10 minutes to preferably less than 60 minutes.
  • the method may include the step of adding lime (CaO) in an amount of from about 2 to preferably less than 80 g per kg dry matter organic material, such as from about 5 to preferably less than 60 g per kg dry matter.
  • the methods of the present invention may comprise the step of diverting an organic material to a first fermenter, under a first set of fermentation conditions, and subsequently diverting said fermented, organic material to a second, or further, fermenter, and fermenting said organic material under a second, or further, set of fermentation conditions.
  • the conditions can be thermophile fermentation conditions and/or mesophile fermentation conditions.
  • the method may include performing the one or more biogas fermentation step(s) at a temperature of from about ⁇ ⁇ 5°C to preferably less than about 65 °C, such as at a temperature of from about 25 ⁇ to preferably less than about 55°C, for example at a temperature of from about 35 °C to preferably less than about 45 °C.
  • the fermentation may be allowed to occur over a time of from about 5 days to preferably less than 15 days.
  • the biogas production is achieved by bacterial anaerobic fermentation of the organic material, and the fermentation method may initially performing the biogas production in the first of two plants by anaerobic bacterial fermentation of the organic material, initially by fermentation with thermophilic bacteria in the first plant, followed by diverting the thermophilicly fermented organic material to a second plant, wherein a fermentation with mesophilic bacteria can take place.
  • Thermophilic reaction conditions include a reaction temperature ranging from 45°C to 75°C, such as a reaction temperature ranging from 55 °C to 60 °C, for example a reaction temperature ranging from 20°C to 45 ⁇ , such as from 30°C to 35°C.
  • the methods of the present invention results in a biogas production output in Nm 3 per 1 ,000 tons biomass input of more than 70,000 Nm 3 , such as more than 80,000 Nm 3 per 1 ,000 tons input, for example more than 90,000 Nm 3 per 1 ,000 tons input, such as more than 100,000 Nm 3 per 1 ,000 tons input, for example more than 1 10,000 Nm 3 per 1 ,000 tons input, such as more than 120,000 Nm 3 per 1 ,000 tons input, for example more than 130,000 Nm 3 per 1 ,000 tons input, such as more than 140,000 Nm 3 per 1 ,000 tons input, for example more than 150,000 Nm 3 per 1 ,000 tons input, such as more than 160,000 Nm 3 per 1 ,000 tons input, for example more than 170,000 Nm 3 per 1 ,000 tons input, such as more than 180,000 Nm 3 per 1 ,000 tons input, for example more than 190,000 Nm 3 per 1 ,000 tons input, for example more than 200,000 Nm 3
  • Nm 3 per 1 ,000 tons input such as more than 500,000 Nm 3 per 1 ,000 tons input, for example more than 1 ,000,000 Nm 3 per 1 ,000 tons input, such as more than 75,000 Nm 3 per 1 ,000 tons input, or for example more than 80,000 Nm 3 per 1 ,000 tons input.
  • methods of the present invention results in an electricity output in KWh per 1 ,000 tons biomass input of more than 200, such as more than 220 KWh per 1 ,000 tons input, for example more than 240 KWh per 1 ,000 tons input, such as more than 260 KWh per 1 ,000 tons input, for example more than 280 KWh per 1 ,000 tons input, such as more than 300 KWh per 1 ,000 tons input, for example more than 320 KWh per 1 ,000 tons input, such as more than 340 KWh per 1 ,000 tons input, for example more than 360 KWh per 1 ,000 tons input, such as more than 380 KWh per 1 ,000 tons input, for example more than 400 KWh per 1 ,000 tons input, such as more than 450 KWh per 1 ,000 tons input, for example more than 500 KWh per 1 ,000 tons input, such as more than 600 KWh per 1 ,000 tons input, for example more than 700 KWh
  • methods of the present invention results in a heat output in MWh per 1 ,000 tons biomass input of more than 200 MWh per 1 ,000 tons input, such as more than 220 MWh per 1 ,000 tons input, for example more than 240 MWh per 1 ,000 tons input, such as more than 260 MWh per 1 ,000 tons input, for example more than 280 MWh per 1 ,000 tons input, such as more than 300 MWh per 1 ,000 tons input, for example more than 320 MWh per 1 ,000 tons input, such as more than 340 MWh per 1 ,000 tons input, for example more than 360 MWh per 1 ,000 tons input, such as more than 380 MWh per 1 ,000 tons input, for example more than 400 MWh per 1 ,000 tons input, such as more than 450 MWh per 1 ,000 tons input, for example more than 500 MWh per 1 ,000 tons input, such as more than 600 MWh per 1
  • methods of the present invention results in a steam output in MWh per 1 ,000 tons biomass input of more than 40 MWh per 1 ,000 tons input, such as more than 50 MWh per 1 ,000 tons input, for example more than 60 MWh per 1 ,000 tons input, such as more than 70 MWh per 1 ,000 tons input, for example more than 80 MWh per 1 ,000 tons input, such as more than 90 MWh per 1 ,000 tons input, for example more than 100 MWh per 1 ,000 tons input, such as more than 105 MWh per 1 ,000 tons input, for example more than
  • 1 10 MWh per 1 ,000 tons input such as more than 1 15 MWh per 1 ,000 tons input, for example more than 120 MWh per 1 ,000 tons input, such as more than 125 MWh per 1 ,000 tons input, for example more than 130 MWh per 1 ,000 tons input, such as more than 150 MWh per 1 ,000 tons input, for example more than 200 MWh per 1 ,000 tons input, such as more than 300 MWh per 1 ,000 tons input, or for example more than 500 MWh per 1 ,000 tons input.
  • a plant for generating biogas from an anaerobic fermentation of processed organic material comprising solid and liquid parts, said plant comprising
  • a lime pressure cooker for hydrolysing a first organic material comprising one or more sources of nitrogen
  • an absorption unit for absorbing and condensing ammonia fluids diverted to the absorption unit from the lime pressure cooker when said first organic material is subjected to lime pressure cooking
  • a mixing tank for mixing lime pressure cooked organic material with a further organic material prior to diverting the mixed, organic materials to one or more fermenters
  • one or more fermenters for anaerobically fermenting said organic materials diverted to said one or more fermenters from said mixing tank, wherein said fermentation results in the generation of biogas
  • a separation unit for separating organic materials diverted to the separation unit from said one or more fermenters, wherein said separation of said organic materials results in the generation of a solid organic material fraction and a liquid fraction comprising one or more sources of nitrogen; and vi) means for diverting said liquid fraction comprising one or more sources of
  • the lime pressure cooker for hydrolysing said first organic material comprising one or more sources of nitrogen is preferably operably connected to a reception station suitable for receiving solid organic material and/or to a reception tank suitable for receiving liquid organic material.
  • the lime pressure cooker is also in one embodiment operably connected to a lime storage tank suitable for diverting lime directly to the lime pressure cooker.
  • the absorption unit for absorbing and condensing ammonia fluids diverted to the absorption unit from the lime pressure cooker preferably comprises a steam condenser and a scrubber.
  • the mixing tank is operably connected to a reception station suitable for receiving solid organic material and/or operably connected to a reception tank suitable for receiving liquid organic material. Also, the mixing tank is in one embodiment further operably connected to the absorption unit for absorbing and condensing ammonia fluids, wherein said connection allows ammonia to be stripped in the mixing tank and diverted to the absorption unit.
  • the plant according to the second aspect of the invention in one embodiment further comprises a silage tank for storage of energy crops.
  • the plant comprises one, or more than one, fermenter for anaerobically fermenting said organic materials, wherein said one or more than one fermenter are serially connected so that organic material having been fermented in a first fermenter under a first set of fermentation conditions can be diverted to a second or further fermenter and fermented under a second or further set of fermentation conditions.
  • the plant according to the present invention does not contain a stripper and sanitation tank connected to the lime pressure cooker and an absorption unit for absorbing ammonia N. Accordingly, the lime pressure cooker is connected directly to the absorption unit and ammonia formed in the lime pressure cooker during operation thereof under practical circumstances is diverted directly to the absorption unit.
  • the lime pressure cooker is also connected to a mixing tank which is connected to the lime pressure cooker and which is not connected to the absorption unit. The mixing tank receives lime pressure cooked biomass from the lime pressure cooker and optionally also biomass which has not been processed in the lime pressure cooker. The mixing tank is connected to one or more biogas reactors.
  • the lime pressure cooker is connected to the one or more biogas reactors and receives from said one or more biogas reactors a liquid fraction comprising ammonia N.
  • the liquid fraction is obtained by removing digestate from liquid biomass removed from the one or more biogas reactors. This can be achieved in a number of ways according to state-of-the-art methods.
  • the obtained liquid fraction can be diverted or recycled back to the lime pressure cooker where the liquid fraction is stripped for ammonia N without mixing the liquid fraction with a further biomass.
  • the liquid fraction is mixed with a further biomass which enters the lime pressure cooker prior to processing and stripping of ammonia N.
  • the liquid fraction can be diverted to the mixing tank and mixed with biomass entering this mixing tank directly and without having been subjected to an initial lime pressure cooking step.
  • stripping of ammonia N from the liquid fraction takes place only by lime pressure cooking and not by any other means.
  • the more than one fermenter comprises at least one primary fermenter suitable for thermophilic fermentation and at least one secondary fermenter suitable for mesophilic fermentation.
  • a gas storage facility is operably connected to the one or more than one fermenters.
  • the bioenergy plant according to the present invention further comprises biogas fermenters comprising one or more service facilities, or maintenance shafts.
  • service facility and maintenance shaft are used interchangeably herein.
  • the service facility is a movable sealing facility comprising of at least one sealing wall made out of a flexible, gas tight fabric, film tube or similar.
  • the sealing facility can be converted from a resting to a sealing position wherein a separation of the service area from the gas compartment is achieved in the sealing position.
  • the sealing facility In the sealing position the sealing facility has a canal-like shape.
  • the sealing facility can be extended telescope-like and is for example comprised of slightly coned cylinder segments which can be extended.
  • the sealing body does not have to be of cylindrical shape but can also have a rectangular or multi- angular or some other shape.
  • there is a guidance element for example a rope or chain with which the sealing facility can be converted at least from the resting to the sealing position.
  • the sealing facility forms a gas curtain which separates the biogas area in the fermenting container from the service area.
  • the actual maintenance of the stirring device can be carried out inside the container or also on the roof or above the roof of the fermenting container roof.
  • the sealing facility with the sealing wall is retracted.
  • the stirring device can be swung to the outer wall and can be winded upwards via the height adjuster.
  • the sealing wall can be lowered through the guidance element until it reaches the fermenting substrate and can dip into it slightly or even more if necessary.
  • the service facility can also comprise a maintenance shaft capable of sealing the interior of the biogas fermenter from an external, aerobic environment. During maintenance, no air would be allowed into the fermenting area - which would lead to a decrease in the gas production by anaerobic bacteria. Furthermore, the maintenance shaft prevents the loss of biogas.
  • the maintenance room can be separated from the fermenting room through a rectangular maintenance shaft, which at normal filling level extends into the liquid. 10 cm of the shaft should at least dip into the liquid, but preferably not more than 15 cm.
  • a rigid shaft can be used for ferments with a low solid amount and for high amounts of solids a shaft with a vertically movable lower part.
  • a sealing device When having a movable lower shaft part a sealing device has to be fitted between the shaft parts to prevent gas leaking into the maintenance area. This is achieved through a sealing canal at the rigid shaft part's end and a fitting collar at the movable part's top. The canal can be filled with water to support the sealing function. The gas production is only disrupted at the maintenance shaft's area.
  • a winch system enables the lifting of the rotary stirrer above the container's surface.
  • For rigid shafts a pipe for connection with the fermenting area is needed.
  • a window pane can be installed into the maintenance hatch if it has not been installed somewhere else. To prevent the stirrer blades from getting damaged while lifting the stirrer a safety frame is to be installed.
  • the plant may further comprise a lime pressure cooker for hydrolysing said first organic material comprising one or more sources of nitrogen is operably connected to a reception tank suitable for receiving liquid organic material.
  • the plant may further comprise a lime pressure cooker for hydrolysing said first organic material comprising one or more sources of nitrogen is operably connected to a lime storage tank suitable for diverting lime directly to the lime pressure cooker.
  • the plant may further comprise an absorption unit for absorbing and condensing ammonia fluids diverted to the absorption unit from the lime pressure cooker comprises a steam condenser and a scrubber.
  • the plant may further comprise a pre-incubation tank is operably connected to a reception station suitable for receiving solid organic material, wherein the mixing tank is also operably connected to a reception tank suitable for receiving liquid organic material.
  • the pre-incubation tank can further be operably connected to the absorption unit for absorbing and condensing ammonia fluids, wherein said connection allows ammonia to be stripped in the pre-incubation tank and diverted to the absorption unit.
  • the plant may further comprise more than one fermenter for anaerobically fermenting said organic materials, wherein said more than one fermenters are serially connected so that organic material having been fermented in a first fermenter under a first set of fermentation conditions can be diverted to a second or further fermenter and fermented under a second or further set of fermentation conditions.
  • the more than one fermenter preferably comprises at least one primary fermenter suitable for thermophilic fermentation and, serially connected thereto, at least one secondary fermenter suitable for mesophilic fermentation.
  • the plant may further comprise a gas storage facility operably connected to the afore-mentioned, one or more biogas fermenters.
  • Figure 1 discloses a biogas plant 100 in which a lime pressure cooker is used to hydrolyze organic material prior to anaerobic fermentation and biogas production.
  • the input biomass can comprise organic industrial waste and/or animal manure and/or energy crops.
  • the biomass is added to one or more reception facilities 105 and subsequently transferred to one or more dosing systems (part of pre-treatment system, refer Figure 2, 215).
  • the biomass is transferred from the one or more dosing systems to one or more primary digesters 1 10.
  • biogas and/or organic material biomass can be transferred to one or more secondary digesters 1 15.
  • Biogas is transferred from the one or more secondary digesters 1 15 to a Combined Heat and Power plant (the CHP unit) 120 which generates power and heat.
  • the generated heat is used for heating of the one or more dosing systems.
  • the digestate generated in the one or more secondary digesters 1 15 is transferred to one or more post processing facilities 125 such as one or more decanters.
  • the output from the decanter is a liquid fraction and a solid fraction.
  • the liquid fraction comprising ammonia N is diverted back to the lime pressure cooker and the ammonia N is stripped.
  • FIG. 2 discloses a pre-treatment system 200 according to the second aspect of the present invention.
  • Biomass comprising solid biomasses and/or liquid biomasses that needs pre- treatment is added to one or more pre-treatment systems 205.
  • steam and/or burnt lime is added to the pretreatment system.
  • NH 3 and steam is transferred from the pre-treatment system 205 to one or more steam condensers 210.
  • the one or more steam condensers result in generation of heat and a liquid fraction.
  • Biomass from the pre-treatment system 205 and optionally liquid biomasses that do not need pre-treatment is transferred to one or more dosing modules 215 and subsequently to one or more digesters 220.
  • free ammonia is transferred from the steam condenser 210 to an ammonia scrubber 225 to which sulphuric acid has been or will be added.
  • (NH 4 ) 2 S0 4 is generated in the ammonia scrubber.
  • (NH 4 ) 2 S0 4 can be used as a fertilizer.
  • Figure 3 discloses an energy system 300 according to the present invention. In one
  • biogas is transferred to one or more gas engines 305 and/or one or more steam boilers 310.
  • the output from the gas engine is transferred to one or more exhaust gas boilers 315 comprising water.
  • the output from the one or more steam boilers 310 and one or more exhaust gas boilers 315 can be transferred to one or more steam storages 320.
  • the steam is finally transferred to one or more pre-treatment systems/batch cookers 325.
  • FIG. 4 discloses the principles of one mode of operation of a biogas plant 400 according to the second aspect of the present invention.
  • Biomass comprising organic materials is transferred to a lime pressure cooker 405 and ammonia N is stripped 410.
  • Lime pressure cooked organic material is mixed in a mixing tank 415 with further organic materials which have not been subjected to lime pressure cooking.
  • the mixed, organic materials are transferred to one or more biogas reactors 420 and subjected to anaerobic fermentation and biogas production.
  • separation 425 a liquid fraction comprising inorganic nitrogen is diverted / recycled to the lime pressure cooker and ammonia N is stripped.
  • Figure 5 discloses one preferred embodiment of the present invention.
  • manure preferably in the form of a slurry, generated in a house or stable (1 ) for the rearing of animals, including domestic animals, such as pigs, cattle, horses, goats, sheep; and/or poultry, including chickens, turkeys, ducks, geese, and the like, is transferred to either one or both of a first pre-treatment tank (2) and/or a second pre-treatment tank (3).
  • the manure preferably in the form of a slurry including, in one embodiment, water such as reject water used for cleaning the house or stable
  • the first pre-treatment tank comprising a stripper tank, where ammonia is stripped by means of addition to the stripper tank of e.g. CaO and/or Ca(OH) 2 .
  • addition of CaO and/or Ca(OH) 2 to the slurry may also take place prior to the entry of the slurry into the first treatment tank or stripper tank.
  • the pre-treatment tank comprising the stripper tank is subjected to stripping and/or heating, and the stripped N or ammonia is preferably absorbed prior to being stored in a separate tank (1 1 ).
  • the stripped N including ammonia is preferably absorbed to a column in the stripper tank comprised in the first treatment tank before being directed to the separate tank for storage.
  • Organic materials difficult to digest by microbial organisms during anaerobic fermentation are preferably pre-treated in a second pre-treatment tank (3) prior to being directed to the first pre- treatment tank (2) comprising the stripper tank as described herein above.
  • Such organic materials typically comprise a significant amounts of e. g. cellulose and/or hemicellulose and/or lignin, e. g. preferably more than 50% (w/w) cellulose and/or hemicellulose and/or lignin per dry weight organic material, such as straws, crops, including corn, crop wastes, and other solid, organic materials.
  • N including ammonia is subsequently stripped from the pre-treated organic material.
  • the slurry is subjected to a thermal and alkali hydrolysis.
  • the temperature and/or the pressure is significantly higher in the second pre-treatment tank (3), which is therefore preferably designed as a closed system capable of sustaining high pressures.
  • the slurry having been subjected to a pre-treatment as described herein above is preferably diverted to at least one thermophile reactor (6) and/or at least one mesophile biogas reactor (6).
  • the slurry is subsequently digested anaerobically in the reactors concomitantly with the production of biogas, i. e. gas consisting of mainly methane optionally comprising a smaller fraction of carbon dioxide.
  • the biogas reactor (6) preferably forms part of an energy plant for improved production of energy from the organic material substrate.
  • Liquid organic material comprising ammonia N can be diverted from the one or more biogas reactors and to either one or both of the first (2) and/or second pre-treatment tanks (3). This is indicated by reference numerals 14 and 15.
  • the biogas can be diverted to a gas engine, and the energy generated from this engine can be used to heat the stripper tank.
  • the biogas can also be diverted into a commercial biogas pipeline system supplying household and industrial customers.
  • One result of this separation is an at least semi-solid fraction comprising almost exclusively P (phosphor), such as an at least semi-solid fraction preferably comprising more than 50% (w/w) P (12).
  • an at least semi-solid fraction preferably comprising almost exclusively K (potassium), such an at least semi-solid fraction preferably comprising more than 50% (w/w) K (13) is preferably also obtained.
  • fractions preferably in the form of granulates obtained after a drying step, including a spray drying step or a slurry drying step, preferably comprise P and/or K in commercially acceptable purities readily usable for commercial fertilisers (10).
  • Such fertilisers may be spread onto crops or agricultural fields.
  • the liquids (9) also resulting from the decanter centrifuge separation step, such as reject water, can also be diverted to agricultural fields, they can be diverted back to the stable or animal house, or into a sewage treatment system.
  • the first pre-treatment tank may be supplied with organic material originating from silage tanks (4) comprising fermentable organic materials.
  • the diversion of such organic materials to the first pre-treatment tank may comprise a step involving an anaerobic fermentation such as e.g. thermophile fermentation tank capable of removing gasses from the silage.
  • an anaerobic fermentation such as e.g. thermophile fermentation tank capable of removing gasses from the silage.
  • straws and e.g. crop wastes originating from agricultural fields (5) may also be diverted to stables or animal houses and later to the first and/or second pre-treatment tank.
  • Figure 6 illustrates an embodiment essentially as described in Fig. 5, but with the difference that only phosphor (P) is collected following decanter centrifuge separation, and water in the form of reject water is collected in a separate tank for further purification, including further removal of N, removal of odours, and the majority of the remaining solids. This may be done e. g. by aerobic fermentation. Potassium (K) may also be separated from the liquids at this stage. Numeral indication in this figure is essentially same as those in Figure 5, therefore indicating the same element/ step.
  • Fig. 7 A; B and C illustrate a biogas reactor fitted with a service facility (700) allowing access to the interior of the biogas reactor.
  • the service facility can comprise a shaft providing a limited exposure to biogas during service of the biogas reactor.
  • the service facility extends from the top of the biogas plant to below the surface of the liquid contents of the reactor.
  • the door in the service facility can be opened e.g. when an internally located stirrer has to be maintained or replaced.
  • the service facility can comprise one or more port holes for easy inspection of the interior of the service facility.
  • thermo-chemical pre-treatment method NiX
  • the thermo-chemical pre-treatment method, NiX was performed with respect to pressure, temperature and base addition, and tested on different types of biomass in batch (part 1 ) and continuous experiments (part 2).
  • NiX treatment is able to create long-term improvements in biomethane potential in a number of diverse and commercially interesting biomasses.
  • the biomasses tested in batch assays were anaerobically digested fibre, (obtained from Morso Bioenergi), cow deep litter, dewatered pig manure, chicken litter and hen litter. Biomethane potential improvements were 34%, 33% 27%, 22% and 2% respectively compared to the untreated biomass.
  • NiX treatment consistently removes approximately two-thirds of the inorganic nitrogen, thus facilitating the use of nitrogen rich substrates for biogas production.
  • the combination of NiX treatment with sudden pressure release and extended thermal treatment was also investigated, however the effect hereof was found to be insignificant.
  • thermophilic CSTR biogas process with thermo-chemical treatment NiX and with chicken litter as mono- substrate was run for four months at thermophilic conditions and for five months at mesophilic conditions.
  • the thermophilic CSTR biogas process could run steadily when the substrate was a mixture of raw chicken litter and water at a ratio of 1 :4.17 (1 kg wet weight of chicken litter and 4.17 kg of water).
  • Applying NiX treatment to the thermophilic CSTR biogas process decreased the NH 4 + - N (ammonium nitrogen) concentration in the digester by 15%.
  • Liquid re-circulation and NiX treatment were applied to the mesophilic CSTR biogas process. Extra water was added to the process only via steam condensation during NiX treatment (0.05 kg-H 2 0 / kg WW chicken litter). The mesophilic process did not result in stable conditions because of lack of water. As a consequence, the TS (total solids) and NH 4 + -N concentration in the digester increased.
  • the methane yield was stable at 297 ⁇ 35 mL CH 4 / g VS (where VS is the organic matter content of the chicken litter) and decreased when the NH 4 + -N concentration in the digester increased beyond 6.4 g / kg WW.
  • NiX treatment improved by 13% the methane yield of the chicken litter (measured in batches) and removed 47% of the NH 4 + -N from the substrate.
  • the major contributing factor to the power production of a biogas plant is the quality of the biomass input.
  • Certain substrates such as glycerol, oil and energy crops, are energy rich and/or easily degradable and are therefore desirable as substrates for biogas production.
  • Other biomass types such as pig and cow slurry, deep litter and poultry litter, are low in energy yield, hard to degrade and/or contain compounds inhibitory to the biogas process.
  • Energy rich substrates are more expensive and harder to come by, and technologies that may improve on the biogas yield of the inexpensive, low energy type biomasses, are increasingly more interesting.
  • Lignin is a macromolecule, which serves to uphold the rigid structure of the plant as well as offer protection against fungi, bacteria and vira. Lignin encompasses the easily degradable cellulose and hemi-cellulose in a compound called lignocellulose, and hence creates a physical barrier for the microorganisms in the anaerobic digestion process. In order to create long term improvements in biogas yield it is thus essential to attack the ligno-cellulosic structure.
  • NiX technology is a registered trademark. It refers to a pre-treatment technology developed to attempt to overcome the problems related to lignified biomasses.
  • NiX combines heat and alkalinity in a pressure cooking vessel to attack and dissolve the ligno-cellulosic structure as well as create an environment for removal of the inhibitory nitrogen in the process.
  • the NiX technology comprises treatments of a biomass with saturated steam until reaching working temperatures between 100 °C and 220 °C in combination with a base.
  • the parameters that are of greatest importance in the process include are:
  • Parameters 4, 5 and 6 were addressed second. Determination of the robustness of the treatment using the "standard" NiX treatment on a variety of biomasses. Determination of the additive effect of Flash and extended treatment.
  • Total solids (TS) contents were determined by heating the sample to 105 °C for a minimum of 24 hours.
  • Volatile solids (VS) contents were determined by burning the sample at 550 °C for 3- 4 hours.
  • the substrates tested were selected based on their commercial potential (availability, cost, etc.) and composition (such that the tested substrates represented a wide variety of biomasses). 4.3.2 Nix (Nitrogen Extraction) treatment
  • the Nix technology consists of a thermo-chemical treatment of the substrate.
  • Substrate is mixed with or without saturated lime (Ca(OH) 2 ) and water to the desired concentration.
  • the treatment is performed in a pilot scale pressure cooker in which saturated steam is used to raise the pressure and temperature. After treatment pressure may be decreased either by passive cooling or by actively releasing vapor from the treatment. Samples were collected and processed in accordance with the process having following treatment and analysis flow.
  • Each batch bottle was prepared by addition of approx. 1 g VS followed by addition of 200 ml_ inoculum (VS ⁇ 1 %). Resulting substrate VS concentration in each of the substrate batch bottles was 5 g substrate VS/L inoculum. From each of the independent Nix treatments 3-6 replicates were incubated.
  • the CH 4 content in the headspace of the batch bottles was measured by GC (Perkin Elmer, Auto-analyzer XL) equipped with a capillary column (wax 0.53 mm ID, 30 m) and a FID detector.
  • TAN Total Ammonium Nitrogen
  • TKN Total Kjeldahl Nitrogen
  • Temperature/pressure and alkaline addition are the parameters expected to have the greatest influence on BMP and nitrogen removal.
  • a set of experiments were set up to determine the optimal temperature and base concentration. The initial experiments were performed on one biomass with varying temperatures and base concentrations, as per the following table.
  • Table 1 Experimental matrix showing the combination of parameters tested to elucidate the optimal combination of temperature and base concentration. Pressures tested were 0 barg, 4 barg and 9 barg. Base concentrations were 0 wt%, 0,25 wt%, 0,5 wt%, 1 wt%, and 2 wt% Ca(OH) 2
  • the experimental matrix consisted of 5 base concentrations, 3 temperatures/pressures and 3 replicates, making up a total of 45 different treatments to be tested. Since each pressure cooking cycle takes 3-4 hours, it was unfeasible to carry out each experimental combination individually. The experiments were thus performed without active pressure release to avoid boiling of the samples, and thus allow more than one treatment per pressure cooking cycle. In other words, the pressure cooker was allowed to cool down without opening any vents to release the pressure. This passive cool down method resulted in very little boiling of the liquid.
  • More than one treatment per pressure cooking cycle is made possible by placing 500 ml_ beakers with chicken manure, wherein each beaker contains varying amounts of Ca(OH) 2 corresponding to either 0%, 0,25%, 0,5%, 1 % or 2% (w/w).
  • each beaker contains varying amounts of Ca(OH) 2 corresponding to either 0%, 0,25%, 0,5%, 1 % or 2% (w/w).
  • Nitrogen removal optimum occurs at 1 %-2% Ca(OH 2 ) addition.
  • Ca(OH) 2 has a low solubility, and it was therefore a possibility that the very soluble NaOH, may behave differently. However, no observable difference was found between the two compounds with respect to nitrogen removal, which may indicate that the non-dissolved Ca(OH) 2(s) functions as a buffer and the equilibrium settles so fast that it is not a limiting factor.
  • BMP assays on Nix treated Chicken Litter were initiated on October 19 th 2010 and were allowed to run for 48 days, with valid data available upto 27 days is considered.
  • BMP assays on Chicken Litter treated with Nix in the absence of saturated lime were initiated on January 17 th 201 1 and run for 81 days.
  • Treating Chicken Litter with Nix technology has a significant effect on BMP, and saturated lime is necessary to obtain optimal improvements.
  • Nix treatment has no effect on removal of organic nitrogen, however total ammonium nitrogen levels are decreased by -65%.
  • TS and VS contents of the Chicken Litter were determined in triplicate prior to Nix treatment.
  • Figure 8A Specific methane yields obtained during the BMP analysis of treated and untreated Chicken Litter are shown in Figure 8A and Figure 8B. All curves show a steady increase in methane yield until day 15. Error bars represent ⁇ 1 standard deviation.
  • Figure 8A illustrates Methane yield from batch bottles with untreated Chicken Litter and Nix treated Chicken Litter with or without an extended thermal treatment at 70 °C.
  • FIG. 8C illustrates a graphical representation of TKN, TAN and Organic nitrogen (Org-N) levels in untreated and treated Chicken Litter.
  • PC Pressure Cooked. Specific values and the resulting nitrogen reductions as a result of Nix treatment are shown in
  • Inorganic nitrogen constitutes about a quarter of the entire nitrogen pool (-24%). Organic nitrogen constitutes the remaining -76%. Using Nix technology inorganic nitrogen is removed to an absolute level of 5,0 g N/kg VS, which constitutes a 65% reduction in TAN. Organic nitrogen is not removed in this treatment. Subsequent prolonged thermal treatment does not remove further nitrogen.
  • Cow Deep Litter was treated with Xergi Nix (Nitrogen Extraction) technology and analyzed for biomethane potential and nitrogen content before and after treatment. Results from untreated Cow Deep Litter is compared with Nix treated Cow Deep Litter to evaluate the effect of the treatment.
  • BMP assays on Nix treated Cow Deep Litter were initiated on October 19 th 2010 and were allowed to run for 48 days. However, due to technical problems only data up to day 27 are valid. BMP assays on Cow Deep Litter treated with Nix in the absence of saturated lime were initiated on January 17 th 201 1 and run for 80 days.
  • NiX treatment of Cow deep litter resulted in a 33% BMP increase compared to untreated substrate.
  • Treating Cow Deep Litter with Nix technology has a significant effect on BMP.
  • Nix treatment has no effect on removal of organic nitrogen, however total ammonium nitrogen levels are decreased by -64%, corresponding to a reduction in total nitrogen of 12%.
  • TKN levels before and after show a reduction in TKN of 3% are very inhomogeneous substrate, from which it is much easier to measure TAN than TKN, and it is thus likely that the measured TKN level after treatment is a result of the heterogenic nature of the substrate. This is corroborated by TKN results on Nix treated Cow Deep Litter, showing a total TKN reduction of 15%.
  • TS and VS contents of the Cow Deep Litter were determined in triplicate prior to Nix treatment.
  • Methane yields have been normalized according to an internal standard.
  • Figure 9B illustrates methane yield from batch bottles with untreated Cow Deep Litter and Nix treated Cow Deep Litter in the absence of saturated lime. All curves show a steady increase in methane yield until day 15. Error bars represent ⁇ 1 standard deviation.
  • Figure 9C The nitrogen content of treated and untreated Cow Deep Litter are shown Figure 9C, which illustrates a graphical representation of TKN, TAN and Organic nitrogen (Org-N) levels in untreated and treated Cow Deep Litter.
  • Inorganic nitrogen constitutes about one fifth of the entire nitrogen pool (-19%). Organic nitrogen constitutes the remaining -81 %.
  • inorganic nitrogen is removed to an absolute level of 3,6 g N/kg VS, which constitutes a 64% reduction in TAN.
  • Such a reduction in TAN alone should lead to a TKN reduction of 12%.
  • measured TKN levels before and after only show a reduction in TKN of 3%.
  • Cow Deep Litter is a very inhomogeneous substrate, from which it is much easier to measure TAN than TKN, and it is likely that the measured TKN level after treatment is a result of the heterogeneous nature of the substrate. This is corroborated by TKN results on Nix treated Cow Deep Litter, showing a total TKN reduction of 15%(see Figure 9C). From this it is concluded that organic nitrogen is not removed in this treatment.
  • GEA Dewatered Pig Manure is the fiber fraction after dewatering using a GEA decanter and will be referred to as "pig fibers" in the following.
  • the pig fibers were treated with Xergi Nix (Nitrogen Extraction) technology and analyzed for biomethane potential and nitrogen content before and after treatment. Results from untreated pig fibers are compared with Nix treated fibers to evaluate the effect of the treatment.
  • BMP assays on Nix treated pig fibers were initiated on October 19 th 201 1 and were allowed to run for 48 days. However, due to technical problems only data up to day 27 are valid. BMP assays on pig fibers treated with Nix in the absence of saturated lime were initiated on January 17 th 201 1 and run for 81 days.
  • Treating pig fibers with Nix technology has a significant effect on BMP, and saturated lime seems to be necessary to obtain optimal improvements.
  • the beneficial effect of Nix treatment is gradually diminished over time in the samples treated without saturated lime.
  • the improvement on BMP shows no tendency to fade.
  • Nix treatment has no effect on removal of organic nitrogen, however total ammonium nitrogen levels are decreased by -64%.
  • TS and VS contents of the pig fibers were determined in triplicate prior to Nix treatment.
  • Figure 10A illustrates methane yield from batch bottles with untreated and NiX treated pig fibers with or without an extended thermal treatment at 70 °C. Methane yields have been normalized according to an internal standard. All curves show a steady increase in methane yield until day 15. Error bars represent ⁇ 1 standard deviation.
  • FIG. 10B illustrates methane yield from batch bottles with untreated pig MANURE and Nix treated pig manure in the absence of saturated lime. Methane yields have been normalized according to an internal standard.
  • This BMP assay was run for 81 days and shows a significant effect of the treatment. The course of the graphs show a peak around day 15, after which the curves drop and stabilise at the current level. This type of behaviour is often observed in BMP assays with low substrate concentrations, and is believed to be caused by an initial overproduction of methane from the inoculum VS, which evens out over time as the inoculum controls catch up.
  • FIG. 10C illustrates graphical representation of TKN, TAN and Organic nitrogen (Org-N) levels in untreated and treated pig fibers.
  • Inorganic nitrogen constitutes a little less than half of the entire nitrogen pool (-46%). Organic nitrogen constitutes the remaining -54%.
  • Nix technology inorganic nitrogen is removed to an absolute level of 6,7 g N/kg VS, which constitutes a 64% reduction in TAN. Organic nitrogen is not removed in this treatment.
  • TAN is further reduced to an absolute level of 4 g N/kg VS corresponding to a 78% reduction.
  • high standard deviations preclude a formal conclusion on this result.
  • AD Anaerobically digested
  • BMP assays were initiated December 10 th 2010 and run for 88 days.
  • Treating the AD fibers with Nix technology has a significant and lasting effect on BMP - Nix treatment has no effect on removal of organic nitrogen, however ammonium/ammonia levels are decreased by >60%.
  • TS and VS contents of the AD fibers were determined in triplicate prior to Nix treatment.
  • Figure 1 1 A Specific methane yields obtained during the BMP analysis of treated and untreated AD fibers are shown in Figure 1 1 A, which illustrates methane yield from batch bottles with treated and untreated AD fiber. All curves show a steady increase in gas yield until day 88. Error bars represent ⁇ 1 standard deviation.
  • Morso Bioenergi AD fiber has been both anaerobically digested and dewatered prior to Nix treatment and analysis.
  • the content of easily digestible organic compounds is thus likely to be very low, with longer digestion times as a result.
  • Based on a kinetic analysis of the gas production the expected yield in a full scale continuous AD plant with a 20 days thermophilic primary digestion and a 10 days mesophilic secondary digestion will be approx. 245 NmL CH4/g VS equal to 78% of the obtained batch yield.
  • Hen litter from Glenrath was treated with Xergi Nix (Nitrogen Extraction) technology and analyzed for biomethane potential and nitrogen content before and after treatment. Results from untreated hen litter is compared with Nix treated litter to evaluate the effect of the treatment.
  • BMP assays were initiated January 24 th 201 1 and run for 79 days.
  • TS and VS contents of the hen litter were determined in triplicate prior to Nix treatment.
  • FIG. 12B illustrates Graphical representation of TKN, TAN and Organic nitrogen (Org-N) levels in untreated and treated hen litter.
  • Specific values and the resulting nitrogen reductions as a result of Nix treatment are shown in Table 17.
  • Total ammonium TAN SD RSD Reduction Reduction nitrogen content (g N/kg VS) (g N/k g % (g N/kg VS) in percent
  • Inorganic nitrogen constitutets a rather small amount of the entire nitrogen pool (-12%).
  • Organic nitrogen constitutes the remaining -88%.
  • the measured removal of inorganic nitogen is therefore somewhat uncertain, as a small release of nitrogen from the organic N pool after the Nix treatment potentially could blur the measurement significantly.
  • the removal of inorganic nitrogen from other biomasses is 60 - 70 % at the described treatment conditions. 5 CSTR investigations
  • Part 1 lab-scale tests (batch);
  • thermophilic operation (phase 1 A, phase 1 B)
  • the objective of the project was to run a stable biogas process fed with chicken litter mono- substrate and with minimal water addition. Also, the ammonia removal with NiX treatment had to be determined.
  • Nitrogen is required by the microorganisms and often the nitrogen source is ammonia
  • NH 3 can be toxic.
  • Chicken litter contains high amount of nitrogen (mainly organic nitrogen) and this results in high NH 4 + -N concentration in the biogas digester
  • thermo-chemical treatment was based on the Nitrogen Extraction NiX treatment and on the results described in the first part of the example (Part 1 ). Details of the treatment conditions used during Part 2 (described in this part of the example) are given in Appendix A: NiX treatment. 5.2 Procedure
  • Xergi's pilot-scale plant was used for the experiments.
  • a 1 -step CSTR biogas process was run at thermophilic conditions (52 °C) during the first period of the experiment until December 2010 (Phase 1 A, Phase 1 B) and at mesophilic conditions (37 °C) from January 201 1 until May 201 1 (Phase 2).
  • Chicken litter was the substrate used.
  • the substrate was a mixture of raw chicken litter and water at a ratio of 1 :4.17 (1 kg wet weight of chicken litter and 4.17 kg of water).
  • the chicken litter was obtained from a local farm (Tjele, Denmark) breeding chickens (broilers). Chicken litter was collected on August 24, 2010, distributed into barrels (approximately 60 kg each) and frozen at -10 °C. The chicken litter contained approximately 2.3% of sphagnum wet weight. The chickens were 42 days old when the chicken litter was collected.
  • the raw chicken litter contained TS 62.8 ⁇ 1 .8%, VS 51 .2 ⁇ 2.7% (average of 1 1
  • Phase 1 A thermophilic, without NiX treatment
  • NiX treatment was made of raw chicken litter and water in the proportions above treated with NiX ( Figure 13B, which illustrates a process configuration during thermophilic operation with NiX treatment). Details of NiX treatment are given in Appendix A: NiX treatment.
  • OLR organic loading rate
  • HRT hydraulic retention time
  • the substrate was a mixture of chicken litter and liquid fraction separated from the effluent of the biogas process.
  • the mixture was treated with NiX before being used as substrate. No water was added to the substrate (aside from steam added during NiX treatment,
  • NiX treatment removed 47% of the NH 4 + -N from the substrate.
  • the rate of pressure reduction after NiX treatment could be regulated by adjusting the opening of the valve for pressure release. This affected the amount of loss, because increasing the rate of pressure reduction increased the amount of material that leaved the NiX treatment unit and thereby was "lost".
  • the optimal rate of pressure release had to maximize NH 4 + -N removal and the amount of treated substrate collected after the treatment (i.e. the loss had to be minimized). Also, the time needed for the NiX treatment had to be minimized.
  • Table 18 shows effect of NiX on the methane yield of the chicken litter.
  • Nitrogen measurements (NH 4 + -N and TKN) were made once per week during the mesophilic operation (Phase 2). The concentration of organic nitrogen was calculated as the difference between TKN and NH 4 + -N.
  • Figure 17 illustrates the nitrogen flow in the system is expressed in g of nitrogen per day, where:
  • AD - biogas digester anaerobic digester
  • This flow is calculated from the measured concentrations (g nitrogen per kg wet weight, measured once per week) and the measured flow rates (kg wet weight per day, measured every day). The averages of two or three nitrogen measurements and of four or five flow rate measurements have been used to calculate the nitrogen flow.
  • Nitrogen balance substrate tank The balance around the substrate tank is closed, as 77 g N / d (as TKN) enter the substrate tank and 76 g N / d leave it.
  • TKN balance biogas digester The TKN balance around the biogas digester shows that 17% TKN is missing: 76 g N / d enter the biogas digester with the substrate and only 63 g N / d leave it with the effluent. The main reason for this is the transient state of the biogas digester at the time of the measurements.
  • Nitrogen balance separation liquid-solid A centrifuge was used to separate the effluent of the biogas digester into the liquid and the solid fraction.
  • the TKN balance around the separation was accurate at 10%, which can be considered satisfactory.
  • NiX treatment removed 47% of the NH 4 + -N, in average ( Figure 16, above).
  • Organic nitrogen was not affected by the NiX treatment or only a very small part of it was converted into NH 4 + -N. Only 7% of the organic nitrogen was missing from the balance and this was within the accuracy of the measurements. 5.3.2 Effect of re-circulation
  • Re-circulation had the overall effect of increasing the TS content of the digester at the rate of 0.4% per week and increasing the NH 4 + -N concentration of the digester at a rate of 0.5 g / kg WW per week. This was due to the lack of water (no water was added to the system, aside from steam during NiX treatment). In the substrate, the VS content was approximately constantly 68% of the TS (therefore the ashes were 32% of the TS). The VS fraction of the TS of the digester increased from 44% in February 201 1 to 55% at the end of May 201 1 , indicating that the conversion of VS into biogas was decreasing. The increase was
  • the HRT was different from the SRT (solids retention time, retention time of the alive microorganisms), Figure 19 illustrates Hydraulic Retention Time (HRT) and Solid Retention Time (SRT).
  • HRT Hydraulic Retention Time
  • SRT Solid Retention Time
  • the HRT was calculated from the flow rate of material leaving the system.
  • the HRT was approximately 145 d. This is the average time that solids and water spend in the system (the system includes the re-circulation).
  • the HRT did not depend on the flow rate of the
  • the SRT was calculated as the average time that the living microorganisms spend in the system.
  • the SRT was 29 ⁇ 5 d. This is acceptable for a mesophilic biogas process.
  • the liquid fraction (re-circulate) contains microorganisms and these are killed during NiX treatment.
  • the retention time of the microorganisms had to be calculated from the flow rate of the material that leaved the digester.
  • the SRT depends on the flow rate of the recirculation.
  • the yield reached the constant 297 ⁇ 35 mL CH 4 / g VS (where VS is the organic matter content of the raw chicken litter).
  • Figure 20 illustrates methane yield during phase 2 (mesophilic operation)
  • Figure 21 illustrates feed flow rate
  • biogas yield main vertical axis
  • NH 4 + -N concentration in the digester secondary vertical axis
  • Figure 22 illustrates TS content of the digester and of the liquid after separation with centrifuge.
  • the NH 4 + -N concentration in the digester was 6.4 g / kg WW and this can be considered the threshold level that caused decreased conversion efficiency or inhibition.
  • the concentration of CH 4 in the biogas was 55% and the tot VFA in the digester was 2000 mg/L.
  • the tot VFA in the digester was 2400 mg/L, just slightly higher than on 10 May.
  • the methane yield was decreasing, but the tot VFA concentration did not show any clear or sharp increase.
  • the methane yield decrease of March 3 - March 7 was due to a feeding pump stop. In the period April 13 - May 7 the yield showed large variations (the points in Figure 20 are scattered) because of technical problems with pumps and with the computer controlling the pilot plant.
  • the TS and NH 4 + -N concentration in the digester always showed increasing trends ( Figure 21 , and Figure 22).
  • the effluent of the digester was separated into the liquid and the solid fraction.
  • the liquid fraction was re-circulated and mixed with the raw chicken litter before being treated with NiX.
  • sedimentation became not effective as the TS% of the material to be separated increased.
  • the purpose was to decrease the TS% in the digester by decreasing the TS% of the separated liquid.
  • lower TS% in the liquid obtained with centrifugation was not sufficient to lower the TS% in the digester.
  • the TS content of the liquid fraction increased as the TS content of the digester effluent increased, i.e. the separation efficiency of the centrifuge used for separation depended on the TS content of the material to be centrifuged.
  • Figure 23 shows the mass balance around the NiX treatment unit for a specific treatment.
  • the data represented are per treatment.
  • the nitrogen balance (NH 4 + -N) showed that NiX treatment removed 55% of NH 4 + -N from the substrate.
  • the concentration of NH 4 + -N in the treated substrate (after NiX treatment) was 3.2 g- NH 4 + -N/kg-WW. These data are from one specific treatment considered. On average, NiX treatment removed 47% NH 4 + -N.
  • NiX treatment removed 47% of the NH 4 + -N from the substrate and decreased by 15% the NH 4 + -N concentration in the biogas digester.
  • NiX treatment was applied with Xergi's thermo-chemical treatment unit.
  • the substrate for NiX treatment were the mixtures of raw chicken litter and water or of raw chicken litter and liquid separated from the digester's effluent.
  • Pressure is expressed as relative pressure above atmospheric pressure (gauge pressure). A pre-heating of the external walls of the chamber and injection of steam on these walls during NiX treatment was made to minimize steam condensation inside the chamber during the treatment. At the end of the treatment, the pressure was released in approximately 2 hours.
  • Thermophilic operation is summarized below:
  • Catalyst 2% Ca(OH) 2 (percentage by wet weight of total mixture)
  • Liquid liquid fraction from effluent biogas digester, 2.61 kg WW / kg WW raw chicken litter Catalyst: 2% Ca(OH) 2 (percentage by wet weight of total mixture)
  • the methane potential was determined in batches, with infusion bottles of 543 mL total volume, at 52 °C.
  • Anaerobic digested effluent from a thermophilic biogas plant (52 °C) was used as inoculum for the batch assays.
  • Inoculum 200 mL and substrate were added into the bottle in the amounts given in Table 19. Control batches with pure cellulose as substrate (for examination of inoculum viability) and blank batches without substrate (to measure the methane production from the inoculum) were included. The assays were made in triplicates.
  • Uric acid was measured once as a preliminary test. Uric acid measurements were made to have a better understanding of the degradation of nitrogen in the system.
  • Uric acid is a non-protein organic nitrogen compound, main end product of purine metabolism and present mainly in urine.
  • uric acid is approximately 10% of the TKN. This result is lower than values from literature, which indicate that uric acid is approximately 60% of total N.
  • the reason for this difference may be an incomplete extraction of uric acid from the sample into the liquid fraction to be injected into the HPLC. Results from HPLC seem reliable, according to the calibration curve.
  • the data in Figure 24 are flowrates, g of nitrogen per day. These have been calculated from the measured concentrations (g of nitrogen per kg wet weight) and the measured flowrates (kg wet weight per day). Therefore, measurement errors and uncertainties have to be taken into account when considering the flows shown in Figure 24.
  • the balance around the NiX treatment unit shows that approximately 6% of organic nitrogen is missing:
  • Parameter values for pre-incubation step refers to degradation of organic nitrogen to ammonium.
  • Temperature optimum for uric acid degrading enzyme is approx. 60°C. Expected optimum temperature indicates that the process is biologically induced by mesophilic microorganisms.
  • the process performs best at low oxidation state and indicates that the process is carried out by facultative anaerobic microorganisms.
  • TS levels >10 %, which have a negative effect on process rate.
  • TS >/ 25 % have negative effect on both rate and final effect.
  • Optimal TS level will depend on biomass and liquid used for dilution.
  • the process is not sensitive to different initial pH-levels in the range from slightly acidic to highly basic.
  • Process minimum cycle time is expected to be less than 84 hours by temperature optimization and kick-start by retention of small fraction of each for seeding.
  • Organic dry matter (VS) loss is in the range 5 - 10 %. Degradation of organic nitrogen can explain nearly all VS loss and even in a worst case scenario still more than 50 %.
  • This example covers characterization and optimization of "mineralization", a process of shifting of organic fraction (OrgN) of the nitrogen pool in animal litter to the inorganic fraction (TAN).
  • the mineralization process is described later in Example 4, where it is shown that the organic fraction (OrgN) of the nitrogen pool in chicken litter could be shifted to the inorganic the inorganic fraction (TAN).
  • the focus is on investigating substrates (chicken litter vs. hen litter), suspension liquid (AD liquid vs. water), pH, water content, temperature, and seeding. Material with an active microbiological flora from a previous incubation is added to the samples to "kick-start" the process.
  • Example 4 Mineralisation of OrgN to TAN was performed both on chicken litter and hen litter.
  • the chicken litter substrate used in Example 4 experiment contained bedding as well as faeces, whereas the hen litter used in the subsequent experiments in this example only contained faeces. It therefore seems likely that this type of mineralisation could occur in most poultry litters, since the two types of poultry substrates are different both in terms of the animal source and the presence of bedding.
  • the mineralisation process is most likely due to a biological process. It is independent of the incubation liquid used and works equally well with AD liquid and water. No methane production is observed in the samples containing hen litter and water. The microbial community able to perform this type of mineralisation is thus inherently present in the poultry manure, and methanogenesis is not a prerequisite for mineralisation.
  • Nitrogen mineralisation levels range from 70%-80% conversion of the total organic nitrogen fraction.
  • Uric acid nitrogen constitutes 50% of the OrgN fraction, and was completely degraded in all analysed samples. Degradation of the remaining OrgN pool (primarily protein bound nitrogen) ranged from 48-60%.
  • TS and VS values are not completely consistent and further accuracy could be obtained by re-analysis. However, losses average around 10% of the total VS pool. Mineralisation of uric acid and protein is estimated to account for at least 80% of this VS loss. The total methane potential loss from mineralisation is less than 4%.
  • Nitrogen mineralisation is very dependent on the water content of the samples.
  • the temperature optimum for the process is in the range 33 °C - 37 °C. High oxygen levels were inhibitory to the reaction.
  • the methods are modified to take into account the evaporation of volatile fatty acids during drying.
  • TAN Total Ammonium Nitrogen
  • TKN Total Kjeldahl Nitrogen
  • VFA Volatile fatty acids
  • the CH 4 content in the headspace of the batch bottles was measured by GC (Shimadzu, 2010) equipped with a capillary column (wax 0.53 mm ID, 30 m) and a FID detector.
  • the specific methane yield (Nml methane per gram substrate VS added) is calculated by subtraction of background, normalizing to standard pressure and temperature (STP) and relating the yield to the quantity of VS added.
  • Experiments were set up sequentially with the purpose of characterizing the mineralization process.
  • the Experiments 1 investigated whether the process could be repeated in poultry substrates different from that used in Example 4 experiment and the effect of substituting AD liquid with water.
  • Experiment 2 tested the effect of water content on the process.
  • Experiment 3 made a rough determination of the temperature optimum, and investigated the effect of different oxygen levels.
  • Experiment 4 made a more exact determination of the temperature optimum, and looked into the effect of seeding the process with an active culture.
  • Experiment 1 was run for 17 days; experiments 2-4 were run for 7 days.
  • Example 4 experiment we show that the mineralisation process worked equally well when chicken litter was suspended in AD liquid or liquid from a buffer tank used to feed the digester.
  • this experiment we investigated the difference between using water and AD liquid for suspension of hen litter. Hen litter was suspended in either AD liquid or water and the process was monitored for TAN concentration. The experiment was run at room temperature (RT) between 17 °C and 20 °C for 17 days with 15% TS.
  • Figure 31 illustrates Development of TAN. Comparison between water and AD liquid as suspension liquid for hen litter. Darker bars: TAN concentration at day 0; Lighter bars: TAN concentration after 17 days incubation according to an embodiment of the invention;
  • Figure 33A illustrates development of TAN at normal oxygen level. It is evident that 33 °C results in faster mineralisation speeds compared to the other temperatures tested.
  • Seeding of the sample during incubation is carried out by adding material from a previous successful incubation.
  • the bacterial cultures are actively growing and metabolising. If the mineralisation process, as extrapolated, is catalysed by bacteria then these are likely to be dormant due to the high TS content of the hen litter. A certain time interval will thus be required after hydration to activate their metabolism, causing a lag-phase before TAN development may be detected. Seeding the sample with an active bacterial population is therefore expected to shorten the lag-phase.
  • Experiment 1 was analysed for organic nitrogen content before and after incubation.
  • Organic nitrogen (OrgN) in poultry litter is bound in uric acid (UA) and proteins.
  • Figure 35 illustrates content of uric acid bound nitrogen and protein bound nitrogen before and after mineralization. From the figure, it can be seen that nitrogen mineralisation levels are not influenced by the type of suspension liquid. UA is 100% degraded while protein bound N is degraded by approximately 40%. On average total mineralisation levels range from 71 % - 80%. 4.7 TS and VS
  • FIG. 36A and Figure 36B shows the dry matter loss (VS) and TS changes during incubation of the samples respectively. Samples were incubated for 17 days at RT.
  • VFA Volatile Fatty Acids
  • VFAs are breakdown products from hydrolytic action on carbohydrates, protein and fat.
  • Acetate is produced during anaerobic breakdown of UA.
  • the VFA is monitored during the experiment and was also monitored in Example 4 experiment.
  • Figure 37 illustrates net VFA production during incubation. The figure shows that there is a significant production of VFA's during the mineralisation process. In particular acetate is increased during incubation but also propanoate and butanoate show significant increases. 4.10 Methane
  • Example 4 experiment showed that there was a significant VS loss during incubation.
  • headspace samples were analysed for methane content.
  • Figure 38 illustrates specific methane production in the incubated samples. The figure shows that there is no methane production in the sample incubated with water. This was suspected as hen litter is not known to contain methanogenic microbes. In contrast, there is a small methane production in the samples containing AD liquid. However, the absolute production only amounts to 2-3% of the theoretical methane potential.
  • Breakdown of simple compounds such as uric acid may be caused by chemical hydrolysis reaction or by microbial metabolism.
  • VS loss is not necessarily coupled to loss in methane potential.
  • one of the first steps is deamination of the amino groups. This occurs independently of whether the environment is aerobic or anaerobic. Since the mineralisation step takes place in both cases, it does not cause a loss in methane potential.
  • Uric acid breakdown thus differs with respect to VS loss depending on the pathway used. Aerobic breakdown causes complete conversion into inorganic compounds, whereas anaerobic breakdown only causes 60% conversion into inorganic compounds (Diirre and Andreesen, 1982).
  • the methane potential loss depends on the loss associated with the part of uric acid that is broken down aerobically. Since uric acid has a theoretical methane potential of 100 NmL/g VS the hen litter loses approx. 5-6 NmL CH 4 per treated gram hen litter VS 5 (corresponding to 2 NmL/g hen litter).
  • the CSTR trial setup consisted of a one-stage mesophilic AD.
  • Effluent was separated and the liquid was used to suspend chicken litter prior to NiX treatment.
  • the treated chicken litter was stored in a pretank from which daily portions were fed into the AD.
  • the cause for the shift is likely hydrolysis of uric acid and/or protein.
  • a significant increase in VFA's during the incubation indicates that the process is microbiological.
  • Uric acid in the chicken litter is completely degraded and may account for up to 60% of the entire production of TAN during incubation.
  • TAN Total Ammonium Nitrogen
  • TKN Total Kjeldahl Nitrogen
  • the centrifuged TAN (cTAN) method was developed to minimize the amount of sampling needed to monitor the shift in nitrogen during incubation. Samples were centrifuged at 3500 x g (rcf) for 12 minutes after which the supernatant was analysed for TAN. Removal of particulate material enabled the sampling of much smaller amounts while still maintaining reproducability. Destruction of samples was performed on a TecatorTM Digestion Unit Auto Lift 20 and destinations were performed on a Buchi K355 distillation unit.
  • VFA Volatile fatty acids
  • Table 24 Overview of experimental setup. All units are in grams. A and B are duplicate setups with identical conditions
  • Table 25 TS and VS levels of the substrate materials
  • TS and VS levels of the mixtures were calculated from the starting amounts used of each substrate (see Table 24). After incubation all samples were analysed for changes in solids content.
  • Figure 40A illustrates TS content of incubated samples
  • Figure 40B illustrates VS content of incubated samples, where darker bars representing Day 0 and lighter bars Day 22 according to an embodiment of the invention;
  • Figure 41 illustrates development of pH and cTAN during incubation with chicken litter inoculated with pretank material (Figure 41 A), with AD liquid - 'neutral' ( Figure 41 B), with AD liquid - alkaline ( Figure 41 C), with AD liquid - acidic ( Figure 41 D), where cTAN data depicted on the right Y-axis and pH on the left Y-axis, according to an embodiment of the invention.
  • Figure 41 illustrates development of pH and cTAN during incubation with chicken litter inoculated with pretank material (Figure 41 A), with AD liquid - 'neutral' (Figure 41 B), with AD liquid - alkaline ( Figure 41 C), with AD liquid - acidic ( Figure 41 D), where cTAN data depicted on the right Y-axis and pH on the left Y-axis, according to an embodiment of the invention.
  • there are significant pH drops during the incubation period In the two setups where pH was not adjusted prior to incubation (Figure 41 A and Figure 41 B) the pH drop
  • Centrifuged TAN and pH provide an insight into the development of the inorganic nitrogen fraction during incubation.
  • cTAN may only be used as a relative measure of the development, as the majority of particular matter has been removed.
  • the absolute nitrogen levels may be seen in Figure 42A - Figure 42E.
  • Figure 42 illustrates TAN, TKN and OrgN levels according to an embodiment of the invention, where Figure 42A illustrates TAN levels before and after incubation, where the increase after 22 days is shown above the lighter bar, Figure 42B illustrates TKN levels before and after incubation, where the decrease after 22 days is shows above the lighter bar, Figure 42C illustrates OrgN levels before and after incubation, where the decrease after 22 days is shown above the lighter bar, Figure 42D illustrates OrgN levels before and after incubation for chicken litter alone, where the decrease after 22 days is shown above the lighter bar, Figure 42E illustrates TANIevels before and after incubation for chicken alone, where the increase after 22 days is shown above the lighter bar.
  • TAN is increased in all samples during treatment (see Figure 42A) ranging from 36% - 48% in the samples inoculated with AD material, up to 56% in the sample with inoculated with pretank material. There seems to be a larger TAN increase in the acidic than in the neutral and alkaline sample. However, it cannot be concluded if this is caused by a more efficient N-hydrolysis or due to ammonia evaporation from the neutral and alkaline samples as a result of higher pH.
  • Total ammonia (TKN) levels only change slightly during the test (see Figure 42B).
  • the TKN loss observed is likely due to either sampling (for cTAN analysis), loss during mixing of the samples, or ammonia evaporation, and is considered insignificant in the following calculations.
  • the change in OrgN is calculated as the difference between TAN and TKN, and may be seen from Figure 42C.
  • the decrease in OrgN in the mixture ranges from 27%-37%. From the substrate controls it can be seen that there is no TAN increase in the inoculum liquids from pretank and AD (Figure 45).
  • the entire TAN increase/ OrgN decrease can thus only be attributed to N-hydrolysis in the added chicken litter.
  • degradation levels range from 37% to 50% in the organic nitrogen fraction of the chicken litter (see Figure 42D).
  • Figure 44 illustrates VFA levels according to an embodiment of the invention, where Figure 44A illustrates VFA levels in substrates, Figure 44B illustrates VFA levels in samples, Figure 44C illustrates change in VFAs during incubation as seen by subtracting substrate VFA levels from the sample VFA levels, and Figure 44D illustrates total VFA before and after incubation.
  • VFA levels were measured in the substrates prior to mixing (see Figure 44A). After incubation (on day 22) substrate controls and all samples were analysed for VFA composition. Absolute VFA levels may be seen in Figure 44B.
  • all samples show a significant change in the composition of volatile fatty acids, There is a clear trend that production of acetic acid and butanoic acid takes place in all samples containing AD liquid, and the amount of propionic acid is decreased. The ratio between acetic acid and butanoic acid becomes higher with increasing starting pH, as does the decrease in propionic acid. The reason for this is not yet known. In the sample containing pretank liquid, the total amount of VFA's are only slightly increased. There is a significant increase in butanoic acid only, and a slight decrease in acetic and propionic acid.
  • the pilot-scale experiments were performed at 37°C in continuously stirred tank reactors with twice daily feedings of NiX-treated chicken litter mixed with recycled liquid from the AD process after separation of non-dissolved fibers.
  • NiX-treatments were carried out in a pilot-scale pressure cooker with addition of 1 .5 % CaO relative to the total batch weight. Each experiment had a duration of more than 6 months during which the effectiveness of the NiX-treatment method was investigated while the process stability and biogas (methane) yield of the AD process was monitored.
  • Model calculations made on the results from Experiment 1 showed that when using chicken litter with a very high dry matter content (62-64 % TS) addition of extra water is needed to run a stable biogas process based on chicken litter as mono-substrate.
  • the amount of water needed will vary with varying dry matter contents in the biomass used and may also change as a function of the re-circulation ratio and on the organic loading rate (OLR).
  • Experiment 2 was carried out in the same way as Experiment 1 , but with more focus on tracking the concentration of nitrogen species during the process steps and the pH-dependent toxicity of the ammonium.
  • the water addition ensured a stabilisation of the dry matter content in the digester at 13 %, which is high compared to normal practice in a full-scale system, but it did not cause problems with mixing or pumping.
  • Ammonium removal during NiX-treatment reached 65 % on average but the ammonium concentration in the digester reached 7.5 g/L before stabilizing.
  • this high ammonium level had a very negative effect on the methane yield, which dropped from an average of 310 mL CH 4 / g organic dry matter to less than half of this level.
  • the potential need for water addition is a combined function of the dry matter content in the biomass, the extent of degradation of dry matter during the AD process and the water loss during separation of the digested effluent.
  • a stable and high methane yield can be obtained from chicken litter as a mono- substrate with recycling of digester liquid, but the yield is highly sensitive to the concentration of ammonium in the digester.
  • Organic nitrogen makes up 70-80 % of the total nitrogen pool in chicken litter and is not affected by the NiX treatment. Approximately 50 % of the organic nitrogen is uric acid while the other half is protein-bound. After NiX treatment more than half of the organic nitrogen is released during storage in the pre-tank and during the AD process itself.
  • Figures 1 to 46 illustrate specific applications and embodiments of the invention, and it is not intended to limit the scope of the present disclosure or claims to that which is presented therein.
  • Figures 1 to 46 illustrate specific applications and embodiments of the invention, and it is not intended to limit the scope of the present disclosure or claims to that which is presented therein.
  • numerous specific details, were set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without some of these specific details and by employing different embodiments in combination with one another. The underlying principles of the invention may be employed using a large number of different combinations.

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Abstract

La présente invention se rapporte à un procédé de traitement de biomasse, de fermentation anaérobie de la biomasse traitée et de production de biogaz. L'invention concerne notamment un système et un procédé de génération de biogaz à partir d'une fermentation anaérobie de matière organique traitée qui comprend des parties solides et liquides.
PCT/DK2012/050397 2011-10-28 2012-10-28 Procédé de fermentation anaérobie et de production de biogaz WO2013060338A1 (fr)

Priority Applications (1)

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EP12790786.3A EP2771474A1 (fr) 2011-10-28 2012-10-28 Procédé de fermentation anaérobie et de production de biogaz

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WO2014177156A1 (fr) * 2013-05-02 2014-11-06 Xergi Nix Technology A/S Procédé de fermentation régulée par le ph et de production de biogaz
ITTS20130003A1 (it) * 2013-08-16 2015-02-17 Igp S R L Procedimento e impianti finalizzati alla rimozione dell'azoto dalle deiezioni avicole
EP2837679A1 (fr) * 2013-08-16 2015-02-18 IGP s.r.l. Procédé et installation pour éliminer l'azote du fumier de volaille
CN106471126B (zh) * 2014-04-01 2021-03-16 达科特有限公司 有营养物回收的生物气工艺
WO2015151036A1 (fr) 2014-04-01 2015-10-08 Ductor Oy Procédé de production de biogaz au moyen de récupération de substances nutritives
KR20160140853A (ko) * 2014-04-01 2016-12-07 둑토르 오이 영양분 회수를 하는 바이오가스 생산방법
EP3126507A1 (fr) * 2014-04-01 2017-02-08 Ductor Oy Procédé de production de biogaz au moyen de récupération de substances nutritives
CN106471126A (zh) * 2014-04-01 2017-03-01 达科特有限公司 有营养物回收的生物气工艺
JP2017511141A (ja) * 2014-04-01 2017-04-20 ドゥクトル オサケ ユキチュアＤｕｃｔｏｒ Ｏｙ 栄養素回収を伴うバイオガスプロセス
KR102466594B1 (ko) * 2014-04-01 2022-11-15 둑토르 오이 영양분 회수를 하는 바이오가스 생산방법
WO2016059621A1 (fr) 2014-10-17 2016-04-21 Massai Giordano S.R.L. Installation et procédé pour le traitement de fumier de volaille
WO2017080565A1 (fr) * 2015-11-15 2017-05-18 Xergi Nix Technology A/S Procédé de fermentation de litière de volaille et production de biogaz
EP3580185A4 (fr) * 2017-03-30 2020-11-18 The University of Queensland Procédé de traitement de boue
US11198632B2 (en) 2017-03-30 2021-12-14 The University Of Queensland Process for the treatment of sludge
EP3865564A1 (fr) * 2020-02-17 2021-08-18 A J Inventing v/Anker Jarl Jacobsen Installation d'hydrolyse de biomasse
CN112481311A (zh) * 2020-11-18 2021-03-12 湖州市南浔广达木业有限公司 一种动物屠宰场垃圾的处理方法及处理装置
WO2022112973A1 (fr) * 2020-11-26 2022-06-02 Carborem S.R.L. Procédé et installation de récupération d'azote ammoniacal d'écoulements gazeux produits par des traitements hydrothermaux
CN114230245A (zh) * 2021-12-17 2022-03-25 海安市鸿泰新材料有限公司 一种养殖场蛋鸡粪的综合利用方法
IT202200002675A1 (it) * 2022-02-14 2023-08-14 Univ Degli Studi Di Napoli Federico Ii Metodo per la produzione di una sostanza

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