WO2010001024A2

WO2010001024A2 - Methanation process starting from plant biomass

Info

Publication number: WO2010001024A2
Application number: PCT/FR2009/051073
Authority: WO
Inventors: Thomas Clivio; Hervé BALUSSON; Hervé DEMAIS
Original assignee: Olmix
Priority date: 2008-06-06
Filing date: 2009-06-08
Publication date: 2010-01-07
Also published as: FR2932188A1; WO2010001024A3; FR2932188B1

Abstract

The present invention relates to the use of an algae cake as an activator for a process for the methanation of a substrate, said algae cake having, in particular, a solids content between 10 and 50% by weight.

Description

PROCESS FOR METHANIZATION FROM PLANT BIOMASS

The present invention relates to an anaerobic digestion process from plant biomass.

Methanation is a series of anaerobic fermentation reactions of organic matter, after which biogas is obtained. Biogas is the collected gas mixture that contains mainly methane (50 to 70%), carbon dioxide, water vapor and hydrogen sulphide. Due to its high methane content, biogas is a valuable energy carrier that can be used as a heat-producing fuel or as a fuel for, among other things, operating thermal engines or capable of generating energy under the influence of heat. other forms such as electrical energy. Industrially, biogas is obtained from the microbial degradation of organic substances in the absence of oxygen in so-called "digester" plants. In nature, this process takes place for example in the bottom of swamps.

The amount of biogas produced at the end of this process depends essentially on the nature of the organic matter. All fermentable organic materials are a priori likely to release biogas during the process of methanation. However, some organic materials are much more methanogenic than others. Fats, especially fats, have the highest yield potential, other organic carbohydrate biopolymers, such as cellulose or hemicellulose, have a slower rate of degradation with a much higher biogas yield. weak (at least half). In practice, the most commonly used raw materials in the anaerobic digestion process are animal manure (especially cattle and pig slurry) for so-called on-farm biogas units. The industrial-scale methanation units preferentially use mixtures of food waste, sewage sludge, flotation fat, grease and waste from the food industry, green waste. Today, the valorization of organic biomass by anaerobic digestion is not yet common in France. In Germany today there are more than 4000 units of "industrial" anaerobic digestion or "on-farm" anaerobic digestion. The mixture of these different raw materials has the drawback of frequently providing a substrate whose speed and yield of methanization are low because this mixture is poor in fermentable carbonaceous elements.

To overcome this major drawback and its impact with regard to the economic interest of the anaerobic digestion process, many countries are now developing the use of agricultural plant biomass. Thanks to certain types of plant biomass, fermentable carbonaceous elements can be added to the methanization mixture, in particular from certain energy raw material cultures. This is particularly the case of maize, which is a raw material with a high methanogenic yield. In Germany, the majority of the biogas plants work with corn silage as an essential complement to the economic profitability of the anaerobic digestion of animal dung.

However, these raw materials, sources of carbon required for anaerobic digestion, should normally find their primary use in human and animal nutrition and, in the current demographic and economic context, their use as a methanogenic agent has become an aberration. economic and a scandal on the societal level. One of the aims of the present invention is to propose an alternative to the use of these food resources by using as a methanogenic agent a resource derived from plant biomass, which can not be used for human or animal nutrition.

The object of the present invention is to propose an anaerobic digestion process using a currently untapped bio-resource.

Thus, the present invention relates to a methanization process of a substrate, comprising a step of co-digestion of said substrate with algal material. The anaerobic digestion process consists in the formation of a biogas according to a biological process involving a complex chain of biochemical reactions (FIG. 1) in which various anaerobic microorganisms participate, and in particular: hydrolytic and fermentative bacteria (the main species belong to the genera Clostridium, Bacillus, Ruminococcus, Enterobacteroides, Propionibactehum and Butivibrio);

acetogenic bacteria (homoacetogens of the genera Clostridium, Acetobactehum, Sporomusa, Acetogenium, Acetoanaerobicum, Pelobacter Butyribactehum or Eubacterium, syntrophes of the genera

Syntrophobacter, Syntrophomonas or Syntrophus and sulfato-reducers of the genera Desulfovibrio, Desulfobacter, Desulfotomaculum, or Desulfomonas); and

- specifically methanogenic bacteria, which are grouped in a group of their own, that of Archae.

Figure 1 is a diagram that describes the major metabolic pathways and the nature of microbial populations involved in anaerobic digestion.

Thus, the method of the present invention implements a bio-resource from the marine world and which therefore does not compete with terrestrial plant productions (such as corn conventionally used in current methanation processes).

Moreover, this bio-resource not only acts as a source of carbon, but also as an activator of the biological process of anaerobic digestion, by increasing the reaction rate and by significantly increasing the yield in terms of volume of biogas produced by unit of organic matter treated, while maintaining a good level of biogas quality in terms of methane levels in the gas mixture, as demonstrated below in the experimental part. In the context of the invention, the term "algae" is intended to cover all marine plant species comprising polysaccharides, and in particular green algae of the ulva (ulva) and Enteromorpha species. These algae are known to proliferate on Atlantic and Mediterranean, and are the source of environmental problems of visual and olfactory pollution, hence their nickname "green tide". They constitute a raw material available and of easy access which one seeks to get rid of and which one seeks if possible to valorize.

According to a particular embodiment, the algal material is an extract of algae, in particular of green algae, and more particularly species ulva and Enteromorpha.

The algae are not used raw, preferably, because in this form they have very little interest in an anaerobic digestion process.

Indeed, untreated as in the context of the invention, their dry matter content is not high enough to start and maintain a methanogenic fermentation process. They also contain fractions that are incompatible with methanation, such as sand and a large amount of salts.

The advantage of the invention is to be able to provide selected and concentrated algae extracts which are the largest part of the insoluble matter extracted after a hydrolysis process of the raw algal material, extracts of algae whose level of dry matter is sufficiently high to be compatible with a methanation process and which will act both as a methanogenic raw material but mainly as an activator of the biological process of anaerobic digestion by providing the anaerobic microorganisms responsible for these biochemical transformations with nutrients which are the limiting factors of their metabolism.

According to a particularly advantageous embodiment, the method according to the present invention comprises a step of co-digestion of said substrate with an extract of algae having a dry matter content of 10% to 50%, preferably 20% to 35%. %, and more preferably from 25% to 35% by weight.

More particularly, the present invention relates to a process for methanizing a substrate consisting of products or by-products. organic of animal or vegetable origin, comprising a step of co-digestion of said substrate with a marc of algae.

In the context of the present invention, the term "algae marc" designates a semi-solid product obtained in the form of a cake after a series of treatments applied to raw algae which are in order a grinding, hydrolysis, centrifugation and pressing. This product contains mainly insoluble organic materials as well as mineral substances.

Preferably, this algae has a solids content of 10% to 50%, preferably 20% to 35%, and more preferably 25% to 35% by weight.

Among the organic products or by-products of animal or vegetable origin, animal and vegetable wastes are preferably used, in particular in the form of mixtures. In particular, it is possible to mention mixtures of animal excrement (slurry, cattle and pigs in particular) but also of food waste, sewage sludge, flotation fat, grease and waste from the food industry, and green waste.

The method of the present invention therefore comprises the use of a mixture consisting of the substrate and the algae marc. However, the method of the invention can also be implemented by directly using the algae marc as a substrate.

The aforementioned algae mark as used in the context of the present invention is preferably obtained from green algae, and in particular ulva and Enteromorpha species.

According to a particularly advantageous embodiment, the aforementioned algae marc is obtained from crude algal material having matured step for 1 hour to 48 hours, preferably 2 hours to 24 hours at a temperature of 70 ⁰ At 100 ^° C., preferably from 85 ° C. to 95 ° C.

This maturation step makes it possible to carry out a self-hydrolysis of the algal material. Preferably, the pomace used in the context of the present invention is obtained according to a process comprising the following steps:

a step of washing and grinding raw algal material to obtain a crushed algae; a step of dilution in water of said ground material to obtain a diluted ground material preferably having a percentage of dry matter of 1 to 20%, preferably of 2 to 10%, and still more preferably of 4 to 6% by weight;

a step of maturation of said ground material diluted for 1 hour to 48 hours, preferably for 2 hours to 24 hours, at a temperature of 70 ^° C. to 100 ^° C., preferably 85 ° C. to 95 ° C., to obtain a mix ; and

a step of separation into two phases of said mixture, in particular by centrifugation or decantation, and recovery of the solid phase, followed by a step of pressing said solid phase, to obtain the algae mark.

The crushing step of the raw algal material makes it possible to reduce the particle size and more particularly to obtain particles whose size is from 100 nm to 100 μm, and preferably from 0.5 μm to 10 μm. The aforementioned ripening step allows the self-hydrolysis of the algal material and is preferably carried out with stirring. At the end of this step, a matured mixture is obtained.

Said matured mixture is then separated into two phases, for example by means of an industrial centrifuge type "decanter". The clarified liquid phase thus obtained is evacuated for other uses while the solid phase thus obtained or thick phase or sludge is subsequently pressed, for example by a type of equipment "belt press".

Thus, the present invention also relates to a process for preparing an algae pomace comprising the following steps: a step of washing and grinding raw algal material to obtain a crushed algae;

a step of dilution in water of said ground material to obtain a diluted ground material preferably having a percentage of solids of 1 to 20%, preferably 2 to 10%, and more preferably 4 to 6% by weight;

The present invention also relates to an algae marc able to be obtained by the process as defined above.

According to another embodiment, the present invention relates to the use of a marc of algae as an activator of a methanization process of a substrate.

In co-digestion with organic materials derived from animal or plant products or by-products, and in particular from animal excrement, this marc of algae makes it possible to improve the performance of biogas production in terms of increasing the quantity but also the speed of production. It can also be used alone, as it is, in the anaerobic digestion process.

Preferably, said algae mark is as defined above, and more particularly has a solids content of 10 to 50% by weight. Said substrate consists of organic products or by-products of animal or vegetable origin, and more particularly of animal and vegetable waste as defined above.

The present invention therefore also relates to the use of a marc of algae as an activator of a methanization process of a substrate, characterized in that the algae marc is obtained from raw algal material, in particular from green algae, preferably ulva and Enteromorpha species, and more particularly according to a process comprising a step of maturing said raw algal material for 1 hour to 48 hours; hours, preferably for 2 hours to 24 hours, at a temperature of

70 ⁰ C at 100 ⁰ C, preferably 85 ° C to 95 ° C.

Without being desired to limit it in any way, the present invention will be further illustrated by the following examples:

EXAMPLES

EXAMPLE 1

Preparation of algae marc 12,025 kg of washed and drained green algae (dry matter from

9.53%) are crushed by a refiner with 3 stages of cuts (Inotec brand) to obtain an algae puree whose average particle size is of the order of 5 microns. These 12 025 kg of mash are mixed with 10 895 liters of water, the mixture being brought to 90 ⁰ C and this temperature is maintained at this level for 2.5 hours and then reduced to 40 ° C gradually over 12 hours. A first phase of concentration thanks to a clarifier (brand Flottweg) allows to obtain 3,325 kg of sludge with 13.08% dry matter. The passage of these sludges in the band press (Flottweg brand) makes it possible to recover 1732 kg of marc of seaweed at 25.10% of dry matter.

EXAMPLE 2

Preparation of seaweed marc

11,983 kg of washed and drained green algae (dry matter of 9.93%) are crushed by a refiner with 3 stages of cuts (of Inotec brand) allowing to obtain a purée of seaweed whose average size of particles is of the order of 5 microns. These 11,983 kg of puree are mixed with 11,400 liters of water, the mixture being heated to 90 ^° C. and this temperature being maintained at this level for 2.5 hours and then brought back to 40 ° C. in a progressive manner over 12 hours. A first phase of concentration thanks to a clarifier (brand Flottweg) allows to obtain 3576 kg of sludge with 14.60% dry matter. The passage of these sludges in the belt press (brand Flottweg) allows to recover 1,689 kg of marc of seaweed at 30.91% of dry matter.

EXAMPLE 3

Methanation process

The incorporation of this marc of algae was tested at the entrance of a methanization pilot in co-digestion with pig manure in variable proportions (tests 1 to 2 and 4 to 6). In parallel (trial n ° 3), the incorporation of maize silage type biomass mixed with pig manure was also tested.

Feeder, seaweed, and maize were fed daily into a fermentor feed hopper in varying proportions as described in the table below:

Every hour, a certain quantity of mixture (200-300 kg) is introduced into the digester, here a double-walled stainless steel tank of 15 000 liters maintained at an average temperature of 38 ° C by circulation of hot water in the double wall . In this digester, the methanogenic bacteria progressively transform the fermentable organic matter into biogas. The biogas produced is recovered in the upper part of the digester and, by simple overpressure, is conveyed into a gas storage buffer tank. The daily amounts of biogas and the daily amounts of the mixture entering the digester are measured by the flow meters.

All operations and measurements are under the control of a Simatex brand automaton specifically developed for the monitoring of industrial biogas production units. The measured results are shown in the table below.

Q MSO / j = Quantity of organic dry matter introduced per day MO = Organic matter

The performance measured in the conditions of the biogas pilot with 25% of algae gives an average production of 604 Nm ³ of biogas per tonne of organic matter and a time of only 8 days to obtain 80% degradation of the biogas. organic material. These results confirm the interest of the algae marc as a methanogenic raw material but especially as an activator element of the methanation process that can be used as a substitute for edible plant materials such as maize.

Claims

1. Use of a marc of algae as an activator of a methanization process of a substrate.

2. Use according to claim 1, characterized in that the algae has a solids content of 10 to 50% by weight.

3. Use according to claim 1 or 2, characterized in that the substrate consists of organic products or by-products of animal or vegetable origin, and more particularly of animal and vegetable waste, in particular selected from slurry, manure, waste. agro-food, sewage sludge, flotation fat and green waste.

4. Use according to any one of claims 1 to 3, characterized in that the algae marc is obtained from green algae, including species ulva and Enteromorpha.

5. Use according to any one of claims 1 to 4, characterized in that the algae marc is obtained from raw algal material having undergone a maturation step for 1 hour to 48 hours, preferably for 2 hours at 24 hours, at a temperature of 70 ⁰ C at

100 ⁰ C, preferably from 85 ° C to 95 ° C.

6. A process for methanizing a substrate consisting of organic products or by-products of animal or vegetable origin, and more particularly of animal and plant waste, comprising a step of co-digestion of said substrate with a marc of algae.

7. Method according to claim 6, characterized in that the algae has a solids content of 10 to 50% by weight.

8. Method according to claim 6 or 7, characterized in that the substrate consists of animal and vegetable waste, in particular selected from slurry, manure, food waste, sewage sludge, flotation fat and green waste. .

9. Method according to any one of claims 6 to 8, characterized in that the algae marc is obtained from green algae, including species ulva and Enteromorpha.

10. Method according to any one of claims 6 to 9, characterized in that the algae pomace is obtained from raw algal material having undergone a maturation step for 1 hour to 48 hours, preferably for 2 hours at 24 hours, at a temperature of 70 ⁰ C at

100 ⁰ C, preferably from 85 ° C to 95 ° C.

11. Method according to any one of claims 7 to 10, characterized in that the algae marc is obtained by a process comprising the following steps:

a step of maturation of said ground material diluted for 1 hour to 48 hours, preferably for 2 hours to 24 hours, at a temperature of 70 ^° C. to 100 ° C., preferably 85 ° C. to 95 ° C., to obtain a mix ; and a step of separating said mixture in two phases, in particular by centrifugation / decantation, and recovery of the solid phase, followed by a step of pressing said solid phase, to obtain the algae mark.

12. Process for the preparation of a marc of algae comprising the following steps:

a step of separating said mixture in two phases, in particular by centrifugation / decantation, and recovery of the solid phase, followed by a step of pressing said solid phase, to obtain the algae mark.

13. Algae mark obtainable by the process as defined in claim 12.