WO2012153189A2

WO2012153189A2 - Process and system for producing biogas from anaerobic digestion of plant biomass in solid phase

Info

Publication number: WO2012153189A2
Application number: PCT/IB2012/001034
Authority: WO
Inventors: Adrianus CORNELIUS VAN HAANDEL; Claudia RODRIGUES BARBOSA
Original assignee: Cetrel S.A.
Priority date: 2011-05-11
Filing date: 2012-05-25
Publication date: 2012-11-15
Also published as: WO2012153189A3; BRPI1102151A2

Abstract

The present invention relates to a process for the production of biogas from lignocellulosic materials, comprising the steps of: (a) treatment of plant biomass by steam explosion; and (b) hydrolysis and anaerobic digestion o the material treated in step (a) by anaerobic bacteria; wherein steps (a) and (b) are carried out in separate reactors, step (b) is carried out in a single reactor and the products of step (b) are biogas and the digested biomass. Alternatively, the hydrolysis and the digestion can be carried out in separate reactors. The present invention further relates to a system for carrying out the process of producing biogas of the present invention, which comprises: (i) first reactor for the treatment of plant biomass by steam explosion; and (ii) second reactor for hydrolysis and anaerobic digestion of the material treated in step (i) by anaerobic bacteria. In a preferred embodiment, both process and system of the invention can further comprise, in the hydrolysis and anaerobic digestion reactor, cellulase enzymes with or without addition of xylanases. In an alternative configuration, the hydrolysis can take place in separate reactors.

Description

Report of the Invention Patent for "BIOGAS PRODUCTION PROCESS AND SYSTEM FROM SOLAR PHASE VEGETABLE BIOMASS DIGESTION".

FIELD OF INVENTION

The present invention is part of the field of green technology by producing biogas from plant biomass in reactors operated in a semicontinuous or continuous process.

BACKGROUND OF THE INVENTION

Concerns about rising energy demand, the accumulation of atmospheric CO ₂ from burning fossil fuels, national energy security coupled with the end of fossil fuels and the development of the rural economy are the main reasons for seeking energy sources. sustainable and renewable materials. Methods, materials and techniques for generating new products and processes that cause less environmental impact and / or help reduce pollution and damage to the environment are encompassed in the field of green technology or environmental technology.

As one of Brazil's main agricultural products, cultivated since the time of its colonization, sugarcane is a potential energy generator, with the advantage of being completely renewable. Brazil is in a very favorable situation regarding sugarcane production, and until the second half of November 2008, approximately 460 million tons of sugarcane were processed in the 2008/2009 harvest. In 2010, approximately 654 million tons of sugarcane were processed in the 2009/2010 harvest.

As a consequence of the increase in ethanol production in recent years, there is the increase of agro-industrial residues from this process, such as sugarcane straw and bagasse. The sugarcane waste production potential (dry matter) represents on average 14% of the sugarcane mass. Thus, for each ton of sugarcane produced, there are 140kg of bagasse and 140kg of straw, and according to data from the 2008/2009 harvest, Brazil is accumulating approximately 130 million tons of waste. duos (straw and sugarcane bagasse) (Seabra. Analysis of technological options for the full use of biomass in the sugarcane sector and its implications. Doctoral dissertation. Unicamp, 298p., 2008). According to data from the 2009/2010 harvest, the accumulation is approximately 183 million tons of waste (straw and sugarcane bagasse).

The composition of sugarcane bagasse and straw is variable; The largest component is cellulose (40-50%), followed by hemicellulose (20-30%) and lignin (25-35%). Ashes, phenolic compounds, fatty acids and other constituents, called extractives, make up the remaining fraction of these plant biomasses (Reddy, N.; Yang, Y. Biofibers from agricultural byproducts for industrial applications. Trends in Biotechnology, v.23, p 22-27, 2005). The cellulosic and hemicellulosic fractions may be hydrolyzed and converted to fermentable sugars by physical (eg steam blast), chemical (eg alkali, acid, solvent, gas) and biological (eg enzyme or fungal) methods.

As economic alternatives for the use of sugarcane bagasse and residual straw, the following can be cited as examples: use as fuel in industrial / farm boilers, use in the paper and cardboard industry, use in microbial biomass production and use in feed. animals.

The observed energy potential for sugarcane residue volume can also be verified in other crops such as rice (rice husk), corn (maize straw), barley (barley straw), wheat. (wheat straw), wood (eucalyptus chips) and banana (banana pseudostem). All of this plant biomass has been the subject of a series of studies for applications in green technologies to obtain products of industrial interest, such as alcohols (eg ethanol, butanol), organic acids (eg lactic, acetic, citric acid). ) and biogas.

Anaerobic digestion is a process performed by a consortium of microorganisms under anaerobic conditions (absence of oxygen) converting complex organic material into simpler compounds and cellular material. The biogas generated is composed of methane, carbon dioxide, water, hydrogen sulfide gas, ammonia, among others, depending on the biomass composition employed. The process is developed in sequential stages involving complex metabolic processes, which depend on the activity of at least four groups of microorganisms, namely: hydrolytic bacteria, responsible for the release of exoenzymes that catalyze the hydrolysis of complex organic polymers such as pectin, hemicellulose and cellulose to sugars, long chain carboxylic acids and glycerol; acidogenic bacteria, which metabolize hydrolysed products to even simpler ones such as short chain carboxylic acids, alcohols, lactic acid, CO ₂ , H ₂ , NH ₃ and H ₂ S as a function of environmental conditions; acetogenic bacteria that convert the products resulting from acidogenic metabolism into acetate, hydrogen and carbon dioxide and, finally, these are converted to methane and carbon dioxide by methanogenic bacteria (Chernicharo, CAL. Anaerobic Reactors. Department of Engineering Sanitary and Environmental-UFMG, 246p., 1997).

Some parameters have a greater significance in the monitoring of anaerobic reactors because they are indicative of the efficiency, operational stage and external or internal changes of processes that occur in the reactor. Alkalinity, pH, volatile fatty acids (VFA) and temperature can be highlighted as the most predominant factors.

The temperature in the anaerobic digestion process has a strong influence on the conversion rate of organic material and on the predominant species in a certain temperature range. There are three temperature ranges that have some relationship to microbial growth in most biological processes, namely: the psychophilic range between 4 and 15 ° C; the mesophilic range of 20 to 40 ° C and the thermophilic range of 45 to 70 ° C (Lettinga, G. Sustainable Integrated Biological Wastewater Treatment. Water Science and Technology, v. 33, n. 3. pp. 85-98, 1996). ).

Alkalinity of a system is its ability to neutralize acids as a result of the presence of chemical species of alkaline nature. Alkalinity is indicative of the buffering capacity of a given system and therefore for high alkalinity it should not be It should be understood that the pH is necessarily high. Volatile fatty acids are closely related to alkalinity. The acids formed in the process tend to lower the pH making it acidic and unsuitable for anaerobic processes. In this sense the buffering effect of the solution avoids sudden drops and frequent pH fluctuations (Chernicharo, CAL. Anaerobic Reactors. Department of Sanitary and Environmental Engineering-UFMG, 246p., 1997).

An example of a solid digestion system for biogas production is described in patent document WO 2011/020000 published on 17.02.2011, in which lignocellulosic materials are employed for biogas production, the process comprising: 1) a system liquid phase digestion using industrial or domestic effluents; (2) mixing the effluent obtained in step (1) containing anaerobic bacteria with lignocellulosic materials from various sources; and (3) anaerobic digestion of biomass obtained in step (2). The invention further cites the possibility of pretreatment of biomass with sodium hydroxide for lignin removal.

The present invention differs from the above by the type of pretreatment employed (steam blast) and the possibility of addition of catalyst (industrial enzymes) combined with anaerobic bacteria to increase productivity and digestion efficiency. Additionally, anaerobic sludge is selected from industrial and domestic effluent treatment plants, and the industrial or domestic effluent digestion step is not part of this invention.

Cellulases are usually a mixture of several enzymes that catalyze cellulose hydrolysis, converting it into reducing sugars (mainly glucose) that can be used by microorganisms to produce industrially interesting inputs. There are three types of cellulases responsible for cellulose hydrolysis: (1) endocellulase - responsible for the disruption of polymeric bonds that give the cellulose crystalline structure; (2) exocellulase - cleaves segments of the chains exposed by endocellulase, generating cellobiose (disaccharide); and (3) beta-glycosidase - hydrolyzes cellobiose, generating glucose monomers. The xylan- These catalyze the hydrolysis of the hemicellulosic fraction of the biomass, producing hydrolysate with about 90% pentoses (mainly xylose and arabinase) (Sun, Y .; Cheng. J. Hydrolysis of lignocellulosic materials for ethanol production: a review. Bioresource Technology, v. 83, pp. 1-11, 2002).

SUMMARY OF THE INVENTION

The present invention relates to a process for producing biogas from lignocellulosic materials, comprising the steps of:

(a) pretreatment of plant biomass by steam explosion; and

(b) hydrolysis and anaerobic digestion of the material treated in step

(a) by anaerobic bacteria, with or without the addition of cellulase enzymes, together or not with xylanase enzymes, where steps (a) and (b) are performed in separate reactors, step (b) is performed in a The only reactor and the products from step (b) are biogas and digested biomass.

The present invention further relates to a system for carrying out the biogas production process also object of the invention which comprises:

(i) a first reactor for steam blast pretreatment of plant biomass;

(ii) a second reactor for hydrolysis and anaerobic digestion of the material treated in step (i) by anaerobic bacteria with or without the addition of cellulase enzymes together or not with xylanase enzymes.

Alternatively, the hydrolysis step may be initiated prior to step (b) in an intermediate reactor with the addition of anaerobic bacteria and enzymes operated under thermophilic condition.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 - Figure 1 is a schematic representation of the system and process of biogas production from plant biomass, with a steam blast pretreatment reactor (10) and an anaerobic digestion reactor (20) without addition of catalyst (mesophilic or thermophilic temperature).

Figure 2 - Figure 2 corresponds to the schematic representation. of the system and process of biogas production from plant biomass, with a steam blast pretreatment reactor (10) and an anaerobic digestion reactor (20), with catalyst addition (mesophilic or thermophilic temperature ).

Figure 3 - Figure 3 is a schematic representation of the system and process of biogas production from plant biomass, with a steam blast pretreatment reactor (10), an intermediate reactor (15) to initiate hydrolysis. in thermophilic condition with addition of catalyst and anaerobic bacteria and an anaerobic digestion reactor (20) (thermophilic temperature).

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a process of producing biogas from lignocellulosic materials, which comprises the steps of:

(a) pretreatment of plant biomass by steam explosion;

(b) hydrolysis and anaerobic digestion of material treated in step (a) by anaerobic bacteria, with or without the addition of cellulase enzymes together or not with xylanase enzymes, wherein steps (a) and (b) are carried out. In separate reactors, step (b) is performed in a single reactor and the products of step (b) are biogas and digested biomass.

In an alternative embodiment, hydrolysis may be previously initiated in an intermediate reactor between steps (a) and (b) under thermophilic condition.

The production of biogas according to the invention is made from vegetable biomass, which can be selected from the group consisting of: sugarcane bagasse, sugarcane straw, rice husk, corn, barley straw, wheat straw, eucalyptus chips, banana pseudostem and mixtures thereof.

The first process step of the invention, step (a), comprises pretreatment of the lignocellulosic material into a first reactor (10) by steam explosion as shown schematically. Figures 2 and 3. Hemicellulose, due to its amorphous structure and lower degree of polymerization than cellulose, is partially or completely hydrolyzed in this pretreatment step, depending on the reaction conditions employed. Said pretreatment also aims at destroying the plant biomass fiber, reducing crystallinity and increasing porosity, in order to facilitate hydrolysis of the cellulosic fraction.

The pretreatment of process step (a) of the invention comprises steam explosion by the application of water vapor to the plant biomass in said first reactor, with temperatures ranging from 150-300 ° C, preferably 160-260 °. C, which corresponds to pressures of 0.62-4.7MPa and reaction time ranging from a few seconds to a few minutes before decompression. Even more preferably, the reaction should be carried out at temperatures in the range of 180-220 ° C and reaction times of 3-15 minutes.

The steam explosion process is the sudden decompression of a pressurized system containing high pressure saturated water vapor and plant biomass. Water under high pressure penetrates the cell structure of the biomass, hydrates the cellulose and hydrolyzes the hemicellulose. (CHEN and others Simultaneous saccharification and fermentation of steam exploded wheat straw pretreated with alkaline peroxide. Process Biochemistry. V. 5-9, 2008). The pentoses of the hemicellulosic fraction can be separated and access of enzymes to cellulose is facilitated. Alternatively, prior to digestion step (b), sugars from the hemicellulosic fraction may be transferred to the liquid phase by a biomass wash step, and this liquid rich in organic material may be sent directly to the anaerobic digester. Pretreated biomass has humidity around 55-60%.

The second process step of the invention, step (b), comprises hydrolysis and anaerobic digestion of the material treated in step (a) in a second reactor (20). The material treated in step (a) undergoes hydrolysis and anaerobic digestion in said reactor (as shown in figures 1, 2 and 3), which can operate under mesophilic or thermophilic conditions, with a temperature in the range of 20-70 ° C. preferably from 37 to 55 ° C. Anaerobic bacteria Robots are added to the reactor, which should be operated at a pH of 5.0-8.0, preferably 6.0-8.0, even more preferably 6.5-7.5. The total solids concentration in the anaerobic digestion and hydrolysis reactor is in the range of 5-50%, preferably 5-15%. The feed of said reactor may be semicontinuous or continuous. Industrial enzymes (cellulases with or without xylanases) can be added to anaerobic digestion combined with anaerobic bacteria to increase the efficiency of hydrolysis and anaerobic digestion.

The pH in step (b) may be controlled by the addition of alkalizing agents (strong or weak bases), preferably sodium hydroxide or urea. Alternatively, pH control can be obtained by recirculating the material contained in the reactor, with or without the addition of alkalinizers.

In the reactor of step (b), the cellulosic and hemicellulosic fractions can be converted to lower molecular weight compounds by anaerobic bacteria and commercial enzymes, cellulases with or without xylanases, with the aim of increasing the efficiency and productivity of the reactions. hydrolysis and anaerobic digestion.

The fungus Trichoderma reesei is the most industrially used microorganism for the production of cellulases and xylanases, but some bacteria are also capable of producing such enzymes, such as Clostridium thermocellum, Ruminococcus albus and Streptomyces sp. (Corridor and others Pretreatment and Enzymatic Hydrolysis of Sorghum Bran. Cereal Chemistry, v.84, p.61-66, 2007). Anaerobic bacteria can be selected from anaerobic sludges from wastewater treatment plants or solid domestic or industrial waste. The microorganisms must be adapted to the medium containing the biomass employed for a period ranging from 20-90 days. The most suitable volumetric organic load applied to the reactor is in the range of 5-25 g COD / L.day, more preferably 10-20 g COD / L.day. This organic load should be increased slowly, ensuring conditions that favor the development of anaerobic bacteria.

The type and dosage of enzymes employed in the process of hydrolysis and anaerobic digestion are dependent on factors such as biomass composition, degree of crystallinity of the polymeric chain, type of pretreatment employed and process conditions, especially temperature and pH.

Hydrolysis of the cellulosic fraction of plant biomass for biogas production may be carried out by the addition of cellulases in amounts of about 0.05-5% by mass of total solids (ST), more preferably 0.5-2.5. Mass% ST. The xylanase is added in an amount sufficient to hydrolyze hemicellulose to xylose at concentrations of 0.001-1 wt.% ST, more preferably 0.05-0.2 wt.%. However, treatment of hemicellulose with the addition of xylanase is not mandatory according to the present invention after steam blast pretreatment.

The anaerobic bacteria of said second reactor (step (b)) are obtained by inoculating the same with 5-40% v / v anaerobic sludge, preferably 10-20% v / v. Such inoculation aims at the conversion of carbohydrates produced in the hydrolysis reaction to organic acids, which can be converted to methane and carbon dioxide in this same reactor of step (b).

In step (b), said second reactor may further comprise a solution of organic nutrients, to provide a suitable medium for the development of anaerobic bacteria. The ideal nutrient solution should contain macro (N-NH ₄ ⁺ , P-P0 ₄ ^{3 "} , Mg, Ca) and micronutrients (Fe, Ni, Zn, Co, etc.) as well as alkalinity (NaHC0 ₃ or KH ₂ P0 ₄ and K ₂ HP0 ₄ ) (Aquino et al. Journal of Sanitary and Environmental Engineering, v.12, n. 2, p. 192-201, 2007) A fraction of the nutrient solution can be composed of vinasse (5-10). 20%), by-product of the distillation process for ethanol production from sugar and alcohol plants.

In step (b), the microorganisms present in the sludge perform all the stages of conversion of organic matter to biogas (hydrolysis, acycogenesis, acetogenesis and methanogenesis) in the same reactor. A solid / liquid separation step is not required prior to step (b) as the Anaerobic digestion occurs in the semi-solid phase. Upon completion of step (b), the digested bagasse may be subjected to solid / liquid separation with recirculation of one of the phases to the solid phase digestion reactor. At this stage filtration, centrifugation or pressing can be used, and the fraction to be recirculated (solid or liquid) to the reactor will be dependent on the separation method employed.

The parameters monitored in the aaerobic digestion and hydrolysis reactor (step (b)) to assist in monitoring reactor stability and performance are pH, temperature, alkalinity, volatile fatty acids, COD (Chemical Oxygen Demand), total solids, suspended solids, volatile solids, biomass density and humidity.

(i) a first reactor for the treatment of plant biomass by steam explosion; and

(ii) a second reactor for hydrolysis and anaerobic digestion of material treated in step (i) by anaerobic bacteria.

Alternatively, the hydrolysis and anaerobic digestion steps may be performed in separate reactors. The hydrolysis step can be started in an intermediate reactor (15), as shown in Figure 3, between steps (a) and (b) in the thermophilic condition with anaerobic bacteria, with addition of cellulase enzymes, with or without the addition of xylanases.

EXAMPLES:

EXAMPLE V.

Sugarcane bagasse was used as biomass material, which was pre-treated in a first steam blast reactor (10), using temperatures of 200 ° C, pressure of 1, 6 MPa (16 bar) and reaction time of 7 minutes. The humidity of the expelled bagasse was around 50%.

The pretreated bagasse was transferred to the second anaerobic digestion reactor (20). Said reactor was inoculated with 20% v / v sludge anaerobic treatment of a brewery effluent treatment system adapted to the substrate (pretreated bagasse). The total volatile solids concentration of the obtained sludge was 32gSTV.L ^"1 and specific methanogenic activity (AME) of 0.3gDQO.gSTV ^~ .day ^{" 1} using standard substrate. The process was carried out under thermophilic condition, temperature around 50 ° C, pH around 7.0, solids concentration around 10%, with retention time of 20 days and semicontinuous feeding. After the digestion step, the digested bagasse was submitted to solid / liquid separation and the solid fraction recirculated to the digester.

The parameters monitored in the second reactor to assist in monitoring its stability and process performance were: pH, temperature, alkalinity, volatile fatty acids, COD, total solids, suspended volatile solids, total volatile solids, total fixed solids, bagasse density and moisture and cake density and moisture.

No catalysts were used in the process, such as industrial enzymes or inorganic acids.

Figure 1 shows schematically the system and process presented in this example.

EXAMPLE 2:

Sugarcane bagasse was used as biomass material, which was pre-treated in a first steam explosion reactor (10), using temperatures of 200 ° C, 1.6 MPa (16 bar) and reaction time of 7 minutes. The humidity of the exploded bagasse was around 50%.

The pretreated bagasse was transferred to the second anaerobic digestion reactor (20). Said reactor was inoculated with 20% v / v anaerobic sludge, with total volatile solids concentration of 32gSTV.L ^"1 and specific methanogenic activity (AME) of 0.3gDQO.gSTV ^{~ 1} .day ^{" 1} using standard substrate, and with a commercial enzyme cocktail composed of cellulases and xylanases. The sludge was purchased from an anaerobic digestion unit of brewery effluents and adapted to the substrate used (pretreated bagasse). The process was carried out under thermophilic condition, with temperature around 50 ° C, pH around 7.0, solids concentration around 10%, retention time of 20 days and semicontinuous feeding. After the digestion step, the digested bagasse was submitted to solid / liquid separation and the solid fraction recirculated to the digester.

The parameters monitored in the second reactor to assist in monitoring its stability and performance were: pH, temperature, alkalinity, volatile fatty acids, COD, total solids, suspended volatile solids, total volatile solids, total fixed solids, density and bagasse moisture and cake density and moisture.

Figure 2 shows schematically the process and system presented in this example.

EXAMPLE 3:

The exploded bagasse was transferred to a hydrolysis reactor (15) and inoculated with 20% v / v anaerobic sludge, with total volatile solids concentration of 32gSTV.L ^"1 and specific methanogenic activity (AME) of 0.3gDQO.gSTV ^"1 day ^'1 using standard substrate, and with a commercial enzyme cocktail composed of cellulases and xylanases. The sludge was purchased from an anaerobic digestion unit of brewery effluents and adapted to the substrate used (pretreated bagasse).

In this reactor, the bagasse cellulosic and hemicellulosic fractions are converted to lower molecular weight compounds (sugars, alcohols and organic acids) by sludge enzymes and bacteria. The process was carried out under thermophilic condition, with temperature around 50 ° C, pH around 5.0, solids concentration around 10%, and retention time of 2 days. The pre-treated bagasse was fed in batches. The solid and liquid fractions from the hydrolysis reactor were transferred to the anaerobic digestion reactor (20) with semicontinuous feeding. Said reactor was inoculated with 30% v / v anaerobic sludge with total volatile solids concentration of 32gSTV.L ^"1 and specific metagenogenic activity (AME) of 0.3gDQO.gSTV ^{~ 1} .day ^{" 1} using standard substrate. . The sludge was purchased from an anaerobic digestion unit of brewery effluents and adapted to the substrate used (pretreated bagasse). The reactor was operated in thermophilic condition, with temperature around 50 ° C, pH around 7.0, solids concentration around 10%, and retention time of 20 days. After the digestion step, the digested bagasse was submitted to solid / liquid separation and the solid fraction recirculated to the digester.

Figure 3 shows schematically the process and system presented in this example.

Claims

. Biogas production process from lignocellulosic materials, characterized by the fact that it comprises the steps of.

(a) pretreatment of plant biomass by steam explosion; and

(b) anaerobic hydrolysis and digestion of material treated in step (a) by anaerobic bacteria;

wherein steps (a) and (b) are performed in separate reactors, step (b) is performed in a single reactor and the products of step (b) are biogas and biodigested biomass.

Process according to Claim 1, characterized in that the vegetable biomass of step (a) is selected from the group consisting of sugarcane bagasse, sugarcane straw, rice husk. , maize straw, barley straw, wheat straw, eucalyptus chips, banana pseudostem and mixtures thereof.

Process according to Claim 1 or 2, characterized in that step (a) comprises the steam explosion process for the treatment of plant biomass in a reactor with a temperature of 150-300 ^° C, preferably 160 ^° C. -260 ° C, and pressure from 0.62 to 4.7 MPa.

Process according to any one of claims 1-

3, characterized in that step (b) comprises hydrolysis and anaerobic digestion of the material treated in step (a) in a reactor that can operate under mesophilic conditions with anaerobic bacteria, pH 5.0-8, 0, preferably 6.0-8.0, even more preferably 6.5-7.5, 5-50% solids concentration, preferably 5-15%, semicontinuous or continuous feeding and temperature of 20-40 ° C, preferably 35-40 ° C.

Process according to any one of claims 1-3, characterized in that step (b) comprises hydrolysis and anaerobic digestion of the material treated in step (a) in a reactor which can operate under conditions anaerobic bacteria, pH 5.0-8.0, preferably 6.0-8.0, even more preferably 6.5-7.5, 5-50% solids concentration, preferably 5-15%, semicontinuous or continuous feeding and temperature 40-70 ° C, preferably 45-55 ° C.

Process according to claims 4 and 5, characterized in that the pH is controlled by the addition of alkalizing agents such as urea and sodium hydroxide, alternatively with recirculation of the liquid fraction after solid / liquid separation of the digested biomass in the reactor, with or without the addition of alkalinizers.

Process according to any one of claims 1-6, characterized in that the reactor bacteria of step (b) are obtained by inoculating said reactor with 5-40-% v / v anaerobic sludge, preferably of 10-20% v / v.

Process according to any one of claims 1-

7, characterized in that the reactor of step (b) further comprises adding a solution of organic nutrients.

Process according to any one of claims 1-

8, characterized in that step (b) further comprises adding cellulase enzymes together or not with xylanase enzymes.

Process according to any one of claims 1-9, characterized in that the bagasse digested in step (b) can be subjected to solid / liquid separation with recirculation of one of the phases to the reactor of step (b).

Process according to any one of claims 1-

10, characterized by the fact that the process can be performed without the addition of industrial enzymes.

Process according to any one of claims 1-

11, characterized by the fact that the process can be performed with the addition of industrial enzymes.

Process according to one of Claims 1-12, characterized in that the biomass obtained in step (a) may be subjected to a washing step for recovery of organic material and that this liquid may be sent directly to the reactor from step (b).

Process according to any one of claims 1-13, characterized in that the bagasse may further be hydrolyzed previously in a hydrolysis reactor prior to the digester of step (b), in the thermophilic condition, temperature in the range of 40 ° C. -70Â ° C, preferably 45-55Â ° C, pH in the range 4-7, preferably 5-6, with the resulting solid and liquid fractions subsequently routed to the reactor of step (b).

System for carrying out the biogas production process as defined in any one of claims 1-14, characterized in that it comprises:

(i) a first reactor for the treatment of plant biomass by steam explosion; and

System for carrying out the biogas production process as defined in any one of claims 1-15, characterized in that the bagasse may further be hydrolyzed previously in a hydrolysis reactor prior to the digester of step (ii). ).