Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/34—Biological treatment of water, waste water, or sewage characterised by the microorganisms used
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/28—Anaerobic digestion processes
• • 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

Definitions

• the present invention relates to a method in the production of biogas.
• the biogas production is mainly or exclusively based on manure and urine from, domestic ani ⁇ mals, the socalled liquid manure, or on raw sludge or activated sludge from sewage treatment works.
• many other waste products may form part of the substrate under fermentation in a biogas reactor, in part as a use ⁇ ful measure to get rid of such waste products, in part to serve as energy supplement and hence increase the yield of biogas which, as is known, predominantly consists of methane.
• Sludge used in biogas reactors has a water content of about 85-95% and hence is rather fluid, and so is liquid manure most frequently.
• fat e.g. triglycerides
• it may rise in the reactor and be caught in floating layers.
• the fat will first become hydrolyzed into free fatty acids and glycerol and at pH about 7 - which is normal in biogas reactors - the free fatty acids will form ammonium soaps because of the nitrogenous compounds in the liquid manure and sludge.
• ammonium soaps may cause serious foaming problems in the gas discharge.
• films of ammonium soaps and possibly alkali metal soaps may form round about the microorganisms and/ or particles of fermentable material and thereby hamper the fermentative metabolism.
• oil or fat as a source of energy for the bacteria, together with a carrier substance of fine-grained alkaline earth minerals.
• oil or fat there is preferably used edible oil or fat and the carrier sub ⁇ stance, e.g. calcium or magnesium carbonate, limestone or
• dolomite causes at least a partial conversion of the oil or fat to alkaline earth metal soap.
• the purpose of using a natural fatty substance is to avoid a high concentra ⁇ tion of organic substances, precarious from a health point of view, which is stated to be possible by an- addition for
• calcium and magnesium soaps there is meant in the present specification with claims not only Ca and Mg salts of fatty acids but generally Ca and Mg salts of lipids.
• lipids there is meant in accordance with 10. the difinition in The Condensed Chemical Dictionary,
• the alkaline earth metal soaps may be added as such; various industrial sources provide residual grease in the form of such soaps, e.g. the food industry and the drug indu ⁇ stry.
• burnt lime is the cheapest calcium source and at the same time has the advantage that heat is evolved in the slaking process to which the lime is sub- jected during the lime treatment of the fat in the aqueous phase.
• the free fatty acids and a high propor ⁇ tion of the mono-, di- and triglycerides are saponified and free glycerol is formed.
• source of alkaline earth metal soap one may therefore according to the in ⁇ vention use the entire glycerol-containing reaction product obtained by the saponification of fats with Ca and/or Mg as energy supplement in the production of biogas; this is because glycerol is an excellent sub ⁇ strate for the bacteria which are active in biogas re ⁇ actors.
• glycerol-containing mixture obtained by the saponi- fication with Ca and/or Mg of waste products and waste material containing oils and fats as energy supplement in the production of biogas.
• the glycerol content also has a promoting effect on suspending the alkaline earth metal soaps in the biogas reactor-
• the effect may either be due to an action of glycerol as a humidifying substance, or due to an intermixing of the glycerol into the soap mass in a manner so as to cause this mass to fall apart in very fine par ⁇ ticles when the glycerol is dissolved in a larger amount of water.
• Calcium soap prepared from glycerides is suspended and moistened far easier than calcium soap prepared from pure fatty acids.
• the saponification of fatty acids and esters of fatty acids and glycerol may be carried out with cal ⁇ cium-containing basic fats, e.g. in the form of lime- precipitated wastewater sludge from purification plants for process water using calcium hydroxide as precipita-- tion agent.
• Such lime-precipitated sludge products often con ⁇ tain organic substances which may be reacted in the bio ⁇ gas reactor.
• a considerable proportion of the fatty acids con ⁇ tent of the fat source e.g. 30-60%, may be present in the form of free fatty acids. This, for instance, is the case with fat skimmed off the fat trap in sewage treatment works, since the biological activity has of- ten been high during transport and the biological decom ⁇ position of oils and fats begins with hydrolysis of the ester bonds.
• Free fatty acids are precipitated immedi ⁇ ately as calcium soap when mixed with Ca(OH) --containing media.
• C OH,fatty acid residue
• C fatty acid residue
• ⁇ f sources of residual grease that may be saponified for use in biogas reactors may be fat scraped off from sewage treatment works, fats from fat traps in the food industry and- sludge from clearing tanks as well as many pre-purification plants. Fat-containing sludge from the clearing of tanks in plants which manufacture or work up animal, vegetable and marine oils frequently contains a considerable excess of lecithins.
• Magnesium salts of fatty acids are just as usable as calcium salts and other sparingly soluble salts with fatty acids for being fermented in rotting tanks includ- ing biogas reactors.
• Basic magnesium compounds are not as easily accessible in the majority of countries as are basic calcium salts. But in some countries burnt dolo ⁇ mite (dolomite is a magnesium-calcium carbonate) is used instead of burnt lime and in that"case it may be a con ⁇ venient source for preparing calcium-magnesium soap.
• Example 2 In a biogas reactor having a capacity of 180 m and being in stable operation with liquid manure as substrate for the fermentation, 2500 kg of sludge from a fat trap in the drain system from a plant for the deep-frying of onions were introduced.
• the sludge contained 5% of soya fat having a FFA number (i.e. content of free fatty acids expressed in percent of the fat content) of 50%, the remainder mainly being water.
• FFA number i.e. content of free fatty acids expressed in percent of the fat content

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• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Microbiology (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Biodiversity & Conservation Biology (AREA)
• Environmental & Geological Engineering (AREA)
• Hydrology & Water Resources (AREA)
• Water Supply & Treatment (AREA)
• Zoology (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Biotechnology (AREA)
• Biochemistry (AREA)
• Bioinformatics & Cheminformatics (AREA)
• General Engineering & Computer Science (AREA)
• General Chemical & Material Sciences (AREA)
• Genetics & Genomics (AREA)
• Treatment Of Sludge (AREA)
• Preparation Of Compounds By Using Micro-Organisms (AREA)
• Fats And Perfumes (AREA)
• Micro-Organisms Or Cultivation Processes Thereof (AREA)
• Processing Of Solid Wastes (AREA)

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Cited By (8)

Citations (4)

• 1987
  • 1987-07-14 DK DK365387A patent/DK171735B1/da not_active IP Right Cessation
• 1988
  • 1988-07-07 WO PCT/DK1988/000112 patent/WO1989000548A1/en unknown
  • 1988-07-14 NZ NZ225414A patent/NZ225414A/en unknown

Patent Citations (4)

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