BRPI1102153A2 - Biogas production process and system from vegetable biomass - Google Patents

Abstract

BIOGAS PRODUCTION PROCESS AND SYSTEM FROM VEGETABLE BIOMASS. The present invention relates to a process for producing biogas from lignocellulosic materials, comprising the steps of: (a) steam blasting plant biomass; and (b) hydrolysis, and anaerobic digestion of the 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 digested biomass. Alternatively, hydrolysis and digestion may be performed in separate reactors. 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 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. In a preferred embodiment, both processes and systems of the invention may further comprise in the anaerobic digestion and hydrolysis reactor cellulase enzymes with or without the addition of xylanases. In an alternative embodiment, hydrolysis may occur in separate reactors.

Description

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

FIELD OF THE INVENTION The present invention falls within the field of green technology,

by the production of biogas from plant biomass in reactors operated in a semi-continuous or continuous process.

BACKGROUND OF THE INVENTION

Concerns about increasing energy demand, the increase in atmospheric CO2 due to fossil fuel burning, national energy security combined with the end of fossil fuels and the development of the rural economy are the main reasons for the search for energy. sustainable energy sources and from 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 the main agricultural products in Brazil, 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 for sugarcane production, and by 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 has been an increase in agro-industrial waste from this process, such as straw and sugarcane bagasse. The production potential of sugarcane (dry matter) residues represents on average 14% of the sugarcane mass. Thus, for each ton of sugarcane produced, there is 140kg of bagago and 140kg of straw, and according to data from the 2008/2009 harvest, Brazil is accumulating approximately 130 million tons of residues (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 amount is approximately 183 million tons of waste (straw and sugarcane bagasse).

The composition of bagasse and sugarcane straw is variable; ο 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 extractive compounds, make up the remnant fragment of these plant biomasses (Reddy, N.; Yang, Y. Biofibers from agricultural byproducts for industrial applications. Trends in Biotechnology, v.23 , p.22-27, 2005). Cellulosic and hemicellulosic fractions may be hydrolysed and converted into fermeritesible agitators by physical (e.g. steam extraction), chemical (e.g. alkalis, acids, solvents, gases) and biological (e.g. enzymes or fungi) methods. .

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

The observed energy potential for sugarcane waste volume can also be found in other crops such as rice (rice husk), maize (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 acid, acetylic acid, citric acid). ) and biogas.

Anaerobic digestion is a process carried out by a consortium of microorganisms under anaerobic conditions (absence of oxygen) converting complex organic material into simpler and more matte compounds.

cellular phone. The generated biogas is composed of methane, carbon dioxide, water, sulfur 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, CO2, H2, NH3 and H2S depending on the conditions of the medium; acetogenic bacteria, which convert the acid metabolism products 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 Sanitary and Environmental Engineering-UFMG, 246p. ， 1997).

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

The temperature in the anaerobic digestion process has a strong influence on the conversion rate of the organic material and on the predominant species in a given temperature range. There are three temperature ranges that have some relationship to microbial growth in most biological processes, namely: the psychrophil range between 4 and 150 ° C; the mesophyll range from 20 to 40 ° C and the thermophile range from 45 to 70 ° C (Lettinga, G. Sustainable Integrated Biological Wastewater Treatment. Water Science and Technology, v. 33, no. 3. p. 85-98, 1996).

Alkalinity of a system and its ability to neutralize acids as a result of the presence of chemical species of alkaline nature. Alkalinity is an indication of the buffering capacity of a

Thus, for a high alkalinity, it should not be understood that pH is necessarily high. Volatile fatty acids maintain a close relationship with alkalinity. The acids formed in the process tend to reduce 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, C.A an ■■ Analogous Reactors. Department of Sanitary and Environmental Engineering-UFMG, 246p., 1997).

A widely used type of anaerobic digester is the UASB (Upflow Anaerobic Sludge Bed) type, which provides intensive contact mechanisms between the affluent substrate and bacteria, with efficiencies ranging from 70 to 85%. Due to their ability to apply high organic loads, coupled with their high cell retention capacity, UASB reactors are considered one of the most practical anaerobic systems in domestic and industrial wastewater treatment. An example of a hydrolysis and digestion system for solids for

biogas production is described in US Patent Document 2008/193994 (published on 14.08.2008, in the name of Chris E. Choate and James H. Lord), in which the raw material is composed of a solid solid waste mixture. sewage, and comprises: 1) a modified biomass production system for converting solid organic waste into uniform biomass; 2) a hydrolysis reactor configured to convert biomass to residual solids and a liquid containing soluble compounds by volatile acid hydrolysis and fermentation; and 3) an anaerobic digester configured to receive liquid waste containing soluble compounds together with sanitary sewage to produce biogas from them.

In the present invention, Iignocellulosic materials from various sources may be used for the production of biogas, wherein step 1 is a pretreatment performed in a hydrolytic reactor through the steam blasting process and the hydrolysis step of the biomass is carried out. with hydrolytic bacteria, and may have the addition of biological catalyst (industrial enzymes) combined with these hydrolytic bacteria. In step 3, only ο

Liquid is removed after the hydrolysis step and added to the anaerobic digestion reactor without the use of any additional substrate as sanitary sewage for biogas production.

US Patent Document 2010/0173354 (published 08.07.2010, on behalf of Bjoern Schwarz et al.) Describes a process for fermentation of renewable silage feedstock, which comprises: 1) Washing and crushing of the material renewable silage feedstock; 2) removal of at least part of the water of the material; 3) hydrolysis of material using activated sludge from the sewage treatment plant and optionally manure; and 4) production of biogas from the hydrolyzed material in fermenters. The steps of treatment of renewable silage, hydrolysis and fermentation raw materials can be performed separately.

The present invention is differentiated by the pre-treatment step employed (steam blasting), raw material and also by the possibility of biological catalyst addition in the hydrolysis step. The biomass is hydrolyzed in step 2 and is liquid from the solid / liquid separation and used in step 3 for biogas production, unlike in US 2010/0173354 ， in which both solid and liquid fragments of hydrolyzed material are used in digesters for the production of biogas.

Cellulases are usually a mixture of several enzymes that catalyze the hydrolysis of cellulose, converting it into reducing agents (mainly glucose) that can be used by microorganisms to produce inputs of industrial interest. Three types of cellulases responsible for cellulose hydrolysis are believed to exist: (1) endocululase - 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. Xylanes catalyze the hydrolysis of the hemicellulosic fragment of biomass, producing hydrolysate with about 90% pentoses (mainly xylose and arabinase) (Sun, Y .; Cheng, J. Hydrolysis of Iignocellulosic materials for ethanol production: Bioresource Technology, v. 83, pp. 1-11, 2002).

SUMMARY OF THE INVENTION This invention relates to a biogas production process comprising the steps of:

(a) pretreatment of plant biomass by explosion

steam;

(b) hydrolysis of material treated in step (a) by hydrolytic bacteria.

typical, whether or not cellulase enzymes are added together or not with xylanase enzymes; and

(c) anaerobic digestion of the hydrolyzed material in step (b); wherein steps (a), (b) and (c) are performed in separate reactors and is the product of step (c) and biogas.

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

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

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

(iii) a third reactor for anaerobic digestion of hydrolyzed material in step (ii).

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 - Figure 1 is a schematic representation of the system and process of producing biogas from plant biomass, with a steam blast pretreatment reactor (10), a hydrolysis reactor (20) and an anaerobic digestion reactor (30), without the addition of industrial enzymes according to the present invention.

Figure 2 - Figure 2 is a schematic representation of the system and process of producing biogas from plant biomass, with a steam blast pretreatment reactor (10), a hydrolysis reactor (20) and an anaerobic digestion reactor (30) with industrial enzyme addition according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a biogas production process comprising the steps of:

(a) pretreatment of plant biomass by explosion

steam;

(b) hydrolysis of material treated in step (a) by hydrolytic bacteria, with or without the addition of eeluase enzymes, whether or not together with xylanase enzymes; and

(c) anaerobic digestion of the hydrolyzed material in step (b);

wherein said steps (a), (b) and (c) are performed in separate reactors and the product of step (c) and biogas.

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

The first step of the inventive process, step (a), comprises the pretreatment of the lignocellulosic material into a first reactor by steam explosion as shown schematically in Figures 1 and 2 (reactor 10). Hemicellulose, having an amorphous structure and a 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 fragment.

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

The steam blasting process consists of the single decompression of a pressurized system containing high pressure saturated water vapor and plant biomass. Water under high pressure penetrates the cellular structure of the biomass, hydrates the cellulose and hydrolyzes the hemicellulose. The pentoses of the hemicellulosic fragment can be separated and access of enzymes to cellulose is facilitated. Prior to hydrolysis step (b), the clusters from the hemicellulosic fragment can be transferred to the liquid phase by a biomass wash step, and this organically rich liquid can be sent directly to step c (anaerobic digestion) . The pretreated biomass has humidity around 55-60%. The second stage of the invention process, step (b), comprises

hydrolysis of the material treated in said step (a) in a second reactor. The material treated in step (a) undergoes hydrolysis in said second reactor (20 'reactor as shown in figures 1 and 2) which can operate with temperature in the mesophilic or thermophilic range, preferably in the range 45-55 ° C. Hydrolytic bacteria are added to the reactor, which should be operated at a pH between 5.0-8.0, preferably 5.0-6.0. The concentration of total solids in the hydrolysis reactor is in the range of 5-50%, preferably 5-15% for this process. Industrial enzymes (cellulases with or without xylanase enzymes) may be added to the reactor at this stage, in conjunction with hydrolytic bacteria to increase hydrolysis efficiency.

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

In the hydrolysis reactor, the cellulosic and hemicellulosic fragments can be converted to lower molecular weight compounds by hydrolytic bacteria. Addition of industrial enzymes, cellulases and xylanases is intended to increase the efficiency and productivity of the hydrolysis reaction, as the hydrolysis product can be readily converted by acidogenic and acetogenic bacteria to volatile organic acids.

The fungus Trichoderma reesei is the most industrially used microorganism for the production of eeluIases and xylanases, but some bacteria are also capable of producing such enzymes, such as Clostridium thermocellum, Ruminococcus albus and Streptomyces sp. (Corretor et al. Pretreatment and Enzymatic Hydrolysis of Sorghum Bran. Cereal Chemistry, v.84, p.61-66, 2007). Hydrolytic bacteria can be selected from anaerobic sludge from domestic or industrial wastewater treatment plants. The microorganisms should be adapted to the medium containing the biomass employed for a period ranging from 20-60 days. The most suitable volumetric organic load applied to the reactor is in the range of 5-30 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 hydrolytic bacteria.

The hydrolysis reactor that will be a component of this process differs from the restorations commonly used for biomass hydrolysis, such as the system used for the production of second generation ethanol. For second generation ethanol, only enzymes are used and the hydrolysis products are carbohydrates. In the present invention, these carbohydrates are converted to volatile organic acids by the acidogenic and acetogenic bacteria present in the reactor.

The type and dosage of enzymes employed in the hydrolysis process are dependent on factors such as biomass composition, degree of crystallinity of the polymer chain, type of pretreatment employed and process conditions, especially temperature and pH. The hydrolysis of the cellulosic fragment of plant biomass for

Biogas can be performed with cellulase additions in amounts of about 0.05-5 mass% of total solids (ST), more preferably 0.5-4 mass% of ST. The xylanase is added in an amount sufficient to hydrolyze the hemicellulose to xylose at concentrations of 0.001-1% by mass of ST, more preferably 0.05-0.2%. However, the treatment of hemicellulose with xylanase adipation is not mandatory.

according to the present invention after pre-treatment with the blow-out.

The hydrolytic bacteria of said second reactor (step (b)) are obtained by inoculating it with 5-40% v / v anaerobic iodine, preferably 10-20% v / v. Such inoculation is aimed at converting the biomass into carbohydrates with subsequent production of organic acids which can be converted to methane and carbon dioxide in the third anaerobic digestion reactor from step (c) detailed below.

In step (b), said second reactor may additionally comprise a solution of organic nutrients for the purpose of stimulating enzyme production by hydrolytic bacteria. The ideal nutrient solution should contain macro (N-NH4 +, P-PO43 ", Mg, Ca) and micro-nutrients (Fe, Ni, Zn, Co, etc.) as well as alkalinity (NaHCO3 or KH2PO4 and K2HPO4) (Aquino et al. Eng. San. Amb. Vol.12 - no. 2 (2007), p. 192-201) A fragment of the nutrient solution can be composed of vinasse (5-20%), byproduct of distillation process for ethanol production from alcohol and sugar mills The amount of nutrients added should be sufficient for the development of hydrolytic bacteria.

After the hydrolysis of step (b) is completed, solid / liquid separation of the hydrolyzed material is performed, which can be done by filtration, pressing or centrifugation. The liquid obtained is forwarded to the next step (c).

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

The third step of the inventive process, step (c), comprises the anaerobic digestion of the hydrolyzed material in said step (b) in a third reactor (reactor 30, as shown in figures 1 and 2). The hydrolyzed material in said step (b) is subjected to anaerobic digestion in said third reactor, which operates at temperature in the mesophilic range, more preferably 30-40 ° C. The pH may be controlled by the addition of alkalizing agents such as urea or sodium hydroxide, and should be kept in the range 6.0-8.0, more preferably 6.0-7.0. Alternatively, pH control can be achieved by recirculating the material contained in the reactor, with or without the addition of alkalinizers.

In the present invention, a UASB-type reactor can be used, fed with the liquid fragment obtained after bacterium hydrolysis by bacteria, with or without the addition of enzymes. The lift speed used is in the range of 0.3-1.5 m / hr, more preferably 0.5-1.0 m / hr, retention time of 4-15 hours, preferably 7-10 hours, and volumetric organic charge of 3-30 gDQO / L.day, preferably 10- gDQO / L.day.

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

(i) a first reactor for the pretreatment of organic material or plant biomass by vapor exposure;

(ii) a second reactor for the hydrolysis of the material treated in step (i) by hydrolytic bacteria, with or without cellulase enzyme addition, together or not with xylanase enzymes; and

(iii) a third reactor for anaerobic digestion of hydrolyzed material in step (ii).

EXAMPLES:

EXAMPLE 1:

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

The pretreated bagasse was transferred to the second reactor (hydrolysis reactor) and its hydrolysis was conducted. The hydrolytic reactor operated in mesophilic condition (37 土 0.5oC), pH around 5.5 and solids concentration around 15%, with semi-continuous feeding. Every two days, the second reactor was fed with exploded bagasse and a portion of the hydrolyzed bag (cake for disposal) was removed, and the retention time of solids was around 20 days.

In the second hydrolysis reactor, the cellulosic and hemicellular

The substrate emulsion used (pretreated bagasse) was converted to lower molecular weight agaric by hydrolytic bacteria. For this purpose, the second hydrolytic reactor was inoculated with 20% v / v of anaerobic iodine, with total volatile solids concentration of 32gSTV.L "1 and specific methanogenic activity (AME) of 0.3gDQO.gSTV" 1 .day "1 using standard substrate. Iodine was purchased from an anaerobic brewery effluent digestion unit and was adapted to the substrate used (pretreated bagasse) for about 30 days.

The parameters monitored in the second hydrolysis reactor, to assist in monitoring the stability and performance of the reactor used in the process, were: pH, temperature, alkalinity, volatile fatty acids, COD1 total solids, suspended volatile solids, total volatile solids, fixed solids. totals, bagago density and moisture and cake density and moisture. After the hydrolysis time (48h), the hydrolyzed bagasse was subjected to solid / liquid separation, and the liquid obtained by filtration containing weldable compounds (leached), rich in agar, was sent to the third reactor. Anaerobic digestion.

No type of catalyst was employed in the process, such as industrial enzymes or inorganic acids. The third anaerobic digestion reactor used was a di-

UASB1 type manager fed with the liquid fragment obtained after bacterial hydrolysis of bagago. The lift speed used was 0.5m / h, retention time around 3h and volumetric organic load suitable for this type of reactor. The third UASB reactor was operated in mesophilic condition (37 ± 0.5oC) and pH around 6.

EXAMPLE 2:

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

The pre-treated berry was transferred to the second reactor (reactor

hydrolysis torch) and its hydrolysis was conducted. The hydrolytic reactor operated in a mesophilic condition (37 土 0.5oC) ， pH around 5.5 and solids concentration around 15%, with semi-continuous feeding. Every two days, the second reactor was fed with exploded bagasse and a portion of the hydrolyzed bagago (cake for disposal) was removed, and the retention time of solids was around 20 days.

In the second hydrolysis reactor, the cellulosic and hemicellulosic fractions of the substrate used (pretreated bagasse) were converted to lower molecular mass agicides by hydrolytic bacteria and commercial enzymes of the cellulase and xylanase types, whose objective was to increase the efficiency. and the productivity of hydrolysis in the second reactor. For this, the second hydrolytic reactor was inoculated with 20% v / v anaerobic iodine, 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 enzymes were diluted in water and applied directly to the bagasse during each feed. Iodine was purchased from an anaerobic digestion unit of and was adapted to the substrate used (pretreated bagago) for about 30 days.The parameters monitored in the second hydrolysis reactor to

To assist in monitoring the stability and performance of the reactor used in the process were: pH, temperature, alkalinity, volatile fatty acids, COD, total solids, suspended volatile solids, total volatile solids, total fixed solids, bagago density and humidity and density and moisture in the pie. After the hydrolysis time (48h), the hydrolyzed bagasse was subjected to solid / liquid separation, and the liquid obtained by

A filtration containing agicide-soluble (leached) 1 compounds was sent to the third anaerobic digestion reactor. The hydrolysis efficiency of the biomass was calculated considering the COD value of the bagasse entering the reactor, COD of the bagasse leaving the reactor and the COD of the leachate, obtained by the analysis of the extracted hydrolyzed bagage liquid. The efficiency of the second hydrolytic reactor increased by about 150% compared to Example 1.

The third anaerobic digestion reactor used was a UASB type reactor reactor, fed with the liquid fragment obtained after the hydrolysis of bagago by bacteria and commercial enzymes. The lift speed used was 0.5m / h, retention time around 3h and volumetric organic load suitable for this type of reactor. The third UASB reactor was operated under mesophilic condition (37 ± 0'5。C) and pH around 6.

EXAMPLE 3:

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

The pretreated bagasse was transferred to the second reactor (hydrolysis reactor) and its hydrolysis was conducted. The hydrolytic reactor operated under thermophilic condition (55 土 0.5土C), pH around 5.5 and solids concentration around 15%, with semi-continuous feeding. Every two days, the second reactor was fed with exploded bagasse and a portion of the hydrolyzed bagago (cake for disposal) was removed, and the retention time of solids was around 20 days.

In the second hydrolysis reactor, the cellulosic and hemicellulosic fragments of the substrate used (pretreated bagasse) were converted to lower molecular weight agaric by hydrolytic bacteria. For this, the second hydrolytic reactor was inoculated with 20% v / v of anaerobic iodine, with total volatile solids concentration of 32gSTV.L "1 and specific methanogenic activity (AME) of 0.3gDQO.gSTV" 1 .day "1 with standard substrate.

Iodine was purchased from an anaerobic digestion unit of brewery effluent and was adapted to the substrate used (pretreated berry) for about 30 days.

The parameters monitored in the second hydrolysis reactor, to assist in monitoring the stability and performance of the reactor used in the process, were: pH, temperature, alkalinity, volatile fatty acids, COD1 total solids, suspended volatile solids, total volatile solids, fixed solids. totals, bagago density and moisture and cake density and moisture. After the hydrolysis time (48h), the hydrolyzed bagasse was subjected to solid / liquid separation, and the liquid obtained by filtration containing aglycemic soluble (leached) compounds was sent to the third anaerobic digestion reactor. . The hydrolysis efficiency of the biomass was calculated considering the COD value of the bagasse entering the reactor, COD of the bagasse leaving the reactor and the COD of the leachate, obtained by the analysis of the liquid extracted from the hydrolyzed bagage. To increase the hydrolysis efficiency, a solution containing specific nutrients was added to promote the synthesis of cellulolytic enzymes by the bacteria present in the anaerobic iodine. The efficiency of the second hydrolytic reactor was about 150% higher than Example 1.

No type of catalyst was employed in the process, such as industrial enzymes or inorganic acids.

The third anaerobic digestion reactor used was a UASB type reactor fed with the liquid fragment obtained after bacterial hydrolysis of bagago. The lift speed used was 0'5m / h, retention time around 3h and volumetric organic load suitable for this type of reactor. The third UASB reactor was operated in mesophilic condition (37 ± 0.5 ° C) and pH around 6 ° C.

EXAMPLE 4:

Sugarcane bagasse was used as biomass material, which was subjected to a pretreatment in a first steam extraction reactor, using temperatures around 200 ° C, pressure 1.6 MPa (16 bar) and reaction time 7 minutes. The moisture of bagago

exploded was around 50%. The pretreated bagasse was transferred to the second reactor (hydrolysis reactor) and its hydrolysis was conducted. The hydrolytic reactor operated in thermophilic condition (55 土 0，5oC), pH around 5.5 and solids concentration around 15%, with semi-continuous feeding. Every two days, the second reactor was fed with exploded bagasse and a portion of the hydrolyzed bag (cake for disposal) was removed, and the retention time of solids was around 20 days.

In the second hydrolysis reactor, the cellulosic and hemicellulosic fractions of the substrate used (pretreated bagasse) were converted to lower molecular mass agicides by hydrolytic bacteria and commercial enzymes of the cellulase and xylanase types, whose objective was to increase the efficiency. and the productivity of hydrolysis in the second reactor. For this, the second hydrolytic reactor was inoculated with 20% v / v anaerobic iodine, 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 cellulase and xylanase. The enzymes were diluted in water and applied directly to the berry during each feed. Iodine was purchased from an anaerobic effluent digestion unit. brewery and was adapted to the substrate used (pretreated bagago) for about 30 days.

The parameters monitored in the second hydrolysis reactor, to assist in monitoring the stability and performance of the reactor used in the process, were: pH, temperature, alkalinity, volatile fatty acids, COD1 total solids, suspended volatile solids, total volatile solids, fixed solids. totals, bagago density and moisture and cake density and moisture. After the hydrolysis time (48h), the hydrolyzed bagasse was subjected to solid / liquid separation, and the liquid obtained by filtration containing weldable compounds (leached), rich in sugars, was sent to the third anaerobic digestion reactor. . The hydrolysis efficiency of the biomass was calculated considering the COD value of the bagasse entering the reactor, COD of the bagasse leaving the reactor and the leachate COD obtained.

by the analysis of the liquid extracted from the hydrolyzed bagasse. To increase the hydrolysis efficiency, a solution containing specific nutrients was added to promote the synthesis of cellulolytic enzymes by the bacteria present in the anaerobic iodine. The efficiency of the second hydrolytic reactor was around 175% over Example 1.

The third anaerobic digestion reactor used was a UASB-type digestor reactor fed with the liquid fragment obtained after bagasse hydrolysis by commercial bacteria and enzymes. The lift speed used was 0.5m / h, retention time around 3h and volumetric organic load suitable for this type of reactor. The third UASB reactor was operated under mesophilic condition (37 土 0.5oC) and pH around 6.

Claims (16)

1. Biogas production process, characterized by the fact that it comprises the steps of: (a) pretreatment of plant biomass by steam explosion; (b) hydrolysis of the material treated in step (a) by hydrolytic bacteria; and (c) anaerobic digestion of the hydrolyzed material in step (b); wherein steps (a), (b) and (c) are performed in separate reactors and is the product of step (c) and biogas. Process according to Claim 1, characterized in that the plant 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 a steam blasting process for the pretreatment of plant biomass in a reactor with a temperature of 160 to 260 ° C. and pressure from 0.62 to 4.7 MPa. Process according to any one of claims 1-3 ', characterized in that the biomass obtained in step (a) may be subjected to a washing step for recovery of organic material from the hydrolysis of the hemicellular fraction, which may be This liquid can be sent directly to the reactor of step (c). Process according to any one of claims 1-4 ', characterized in that step (b) comprises hydrolysis of the material treated in step (a) in a reactor that can operate under metallurgical conditions; with hydrolytic bacteria, pH 5.0-8.0, preferably 5.0-6.0, concentration of solids 5-50%, preferably 5-15%, semi-continuous or continuous feeding and temperature 20-20 ° C. 70 ° C, preferably 30-40 ° C. Process according to any one of claims 1-4, characterized in that step (b) comprises hydrolysis of the material treated in step (a) in a reactor that can operate under thermophilic conditions. with hydrolytic bacteria, pH 5.0-8.0, preferably -5.0-6.0, 5-50% solids concentration, preferably 5-15%, semicontinuous or continuous feeding and temperature 20-70 ° C, preferably 45-55 ° C. Process according to Claims 5 and 6, characterized in that the pH is controlled by the addition of alkalizing agents such as urea and sodium hydroxide, alternatively with recirculation of the material contained in the reactor with or without the addition. of alkalinizers. Process according to any one of claims 1-7, characterized in that the hydrolytic bacteria from the reactor of step (b) are obtained by inoculating said reactor with 5-40-% v / v anaerobic iodine, preferably from 10-20% v / v. Process according to any one of claims 1-8, characterized in that the reactor of step (b) further comprises adding an organic nutrient solution. Process according to any one of claims 1-9 ', characterized in that step (b) further comprises the addition of cellulase enzymes in conjunction or not with xylanase enzymes. A process according to any one of claims 1-10 'wherein step (b) further comprises solid / liquid separation of the hydrolyzed material from step (b), wherein the liquid with - having soluble organic material is obtained and directed to step (c). Process according to any one of claims 1-11, characterized in that step (c) comprises the anaerobic digestion of the hydrolyzed material in step (b) in a reactor having mesophilic conditions with temperature preferably 30-40 ° C, pH 6.0-8.0, preferably 6.0-7.0. Process according to Claim 12, characterized in that the pH is controlled by the addition of alkalizing agents such as urea and sodium hydroxide, alternatively with recirculation of the material contained in the reactor with or without the addition of alkalinizers. Process according to any one of claims 1-13, characterized in that the process can be carried out without the addition of industrial enzymes. Process according to any one of claims 1-14, characterized in that the process can be carried out with the addition of industrial enzymes. System for carrying out the bio-gas production process as defined in any one of claims 1-15, characterized in that it comprises: (i) a first reactor for the pretreatment of plant biomass by blast steam; (ii) a second reactor for the hydrolysis of the material treated in step (i) by hydrolytic bacteria; and (iii) a third reactor for anaerobic digestion of hydrolyzed material in step (ii).