WO2018047200A1

WO2018047200A1 - A process for generation of biogas from organic matter via its liquefaction to liquid biocrude

Info

Publication number: WO2018047200A1
Application number: PCT/IN2017/050385
Authority: WO
Inventors: Arvind Mallinath Lali; Manju Bishan SHARMA; Hitesh Suresh PAWAR; Suhas Sundarrao GORE
Original assignee: Arvind Mallinath Lali
Priority date: 2016-09-06
Filing date: 2017-09-06
Publication date: 2018-03-15

Abstract

The present invention relates to anaerobic digestion (AD) process for generation of biogas in near theoretical yields and enhanced productivities from liquid biocrude obtained from a continuous, high yield process operating under moderate temperature and pressure for liquefaction of organic matter. The basis of the invention is the surprisingly excellent amenability of liquid biocrude to anaerobic digestion, and hence the invention imparts great ease and high efficiency to the overall process despite the variable quality of solid organic matter. AD of liquid biocrude results in more than 90% COD reduction with biogas yield greater than 90% containing at least 55% (v/v) methane at OLRs more than 15 g COD/1, day in less than 24 h. The biogas produced can be used for direct replacement of petro-CNG as transport fuel or as power for electricity generation.

Description

A process for generation of biogas from organic matter via its liquefaction to liquid biocrude

TECHNICAL FIELD

[0001] The present invention relates to a process for rapid generation of biomethane in high yield from organic matter, and which involves dual steps of liquefaction of organic matter to liquid biocrude followed by anaerobic digestion of the obtained liquid biocrude.

BACKGROUND OF INVENTION

[0002] Providing adequate and affordable energy is essential for eradicating poverty, improving human welfare and raising living standards worldwide. Organic waste matter can be a viable option for the generation of energy in coming decades since utilization of these achieves the dual goal of cleaning cities as well as generation of energy. Thus, the organic waste has emerged as major environmental issues in India due to lack of proper management. Studies reveal that about 90% of the organic waste is disposed of unscientifically in open dumps and landfills or burnt creating problems to public health and the environment. Land-filling poses serious pollution hazards, including ground water pollution, air pollution, and soil contamination. Moreover land- filling and composting require large surface areas (Environmental Technology, 2013, 34, 13-14, 2085-2097) and are not suitable for countries like India. Several conventional biological, and chemical methods to convert organic matter into energy are known in the art but each of them are associated with several drawbacks. While the biological methods are too slow and non-eco- friendly, the thermal methods are expensive in both capital and operating parameters. Incineration is capable of reducing the waste volume and demands lesser space as compared to land filling but is not ideal for low calorific value substrates. Moreover, the high capital, maintenance and pollution control cost associated with the process makes incineration beyond the reach of developing countries.

[0003] Gasification and pyrolysis though hold distinct promises, but have limitations due to moisture content and heterogeneous nature of the organic matter. Known technologies for handling organic matter are resource intensive and cost money to operate while wasting the carbon content present in the organic matter. As a result, the developing and the less developed countries find it difficult to operate the waste treatment plants.

[0004] Anaerobic digestion (AD) has been tried but the sheer time (hydraulic retention time or HRT) taken by the digesters (between 30-50 days) for conversion to biogas, coupled with production of sludge as by-product waste, makes the technology unsuitable. Moreover, the development of AD technologies for treatment of organic matter is more recent and less mature due to its complex, heterogeneous, and recalcitrant nature. One of the major challenges of AD of organic matter is their slow digestibility and the rate-limiting hydrolysis step (Journal of Biomedicine and Biotechnology, doi 10.1155/2011/953065, 2011) and hence there is need for strategies to improve the properties of organic matter thus making it more amenable and homogenous for rapid and efficient anaerobic digestion. Yet, of all the biological methods, AD of organic matter to biogas appears to be the most attractive biological treatment due to the high energy recovery linked to the process and its limited environmental impact and will provide environmental conservation and public health benefits.

[0005] Organic matter is majorly composed of 75-80% of biodegradable components that can be efficiently converted into carbon rich fuel. Biomethane production via AD is one of the clean energy options for the sustainable utilization of organic matter. Basically, AD is the consequence of a series of metabolic interactions among various groups of microorganisms. Methane production is a complex multi-step process which is divided into four phases: (a) hydrolysis, (b) acidogenesis, (c) acetogenesis and (d) methanogenesis and these individual steps are carried out by different class of microbes. In the first phase, hydrolytic bacteria secrete enzymes to hydrolyze polymers to simple monomers such as glucose and amino acids. The acidogenic or acetogenic bacteria convert these monomeric fragmented organic molecules to higher volatile fatty acids (VFAs), H₂, and acetic acid. Finally, the methanogens convert these VFAs into CH₄ and C0₂.

[0006] In the overall AD process for biomethane production, hydrolysis to simpler monomeric components is the rate limiting step as it takes almost 10-12 days for breakdown of complex polymeric substances depending upon the microbial consortium and conditions. Moreover, the heterogeneity or diversity of any organic matter further adds to prolonged hydrolysis phase and thus longer HRT resulting in slow biogas production rate and hence low productivities. Thus, in order to increase the overall rate of biogas process it is very important to generate a liquid stream of uniform composition and easy digestible simple non-complex components. The present disclosure aims at using liquefaction process to produce liquid biocrude which when subjected to well designed AD process yields biomethane in near theoretical yields with improved productivities.

[0007] WO2016/030480 discloses a method with use of enzyme for the solubilisation of municipal solid waste (MSW) with the resulting liquid being used for the production of bioethanol or biogas. But the recovery and reuse of enzyme is complex and an energy intensive unit operation for such a diverse feed. The high cost of enzyme is also a major factor for the development of techno-commercial process.

[0008] WO2013140416 discloses a design of a compact anaerobic digestion system to convert household waste materials into methane rich biogas and use of concentrated compost slurry for agriculture soil applications. They have fabricated biodigesters which generate biogas having CH4 content greater than 75% and carbon dioxide content less than 25%, and gas production rate with a ratio of 1 or above with respect to volume of digester.

[0009] US5389258 describes anaerobic decomposition of organic wastes and biogas generation in which solids or semi solids are fed to a reactor at the top and fermented liquor is collected at the bottom and mixed with the solids with fresh solids using pumps and elaborate systems. The use of such method for waste treatment encounters the problems of cumbersome unit operation and lower productivity.

[0010] TERI (Tata Energy Research Institute) has reported a modified two-phasic high-rate digester for fibrous and semi-solid municipal solid waste. These processes consist of extracting a high COD (-15,000 -20,000 mg/1) organic leachate from the vegetable waste in an acidification reactor and treating the leachate in an up flow anaerobic sludge blanket (UASB) reactor. But treatment and disposal of the liquid is a serious problem in the process.

[0011] Hartmann et al., {Water Sci. Technol. 2006, 53, 8, 7-22.) discloses the use of organic MSW for the production of biogas by anaerobic digestion with exploration of mesophilic and thermophilic bacteria in a single-stage and multi-stage processes. The highest biogas yields are achieved by means of wet thermophilic processes at OLRs > 6 kg-VS/m d .

[0012] Sivanesan et ah, (Journal of Hazardous Materials. 2007, 141, 301-304) describes anaerobic digestion process for production of biogas from municipal solid waste (MSW) and domestic sewage by using batch type of reactor at 26 to 36°C temperature and HRT of 25 days. They have operated process at optimum organic loading rate of 2.9 kg of VS/m³.day.

[0013] Li et al, (Bioresource Technology 100, 2009, 112-129) discloses study of MSW, a mixture of MSW and paper waste, a mixture of MSW and biosolids, and a mixture of paper and biosolids under thermophilic digestion at 50°C for 20 days and obtained biogas yield of 457- 557mL/g VS.

[0014] Getahun et ah, {Environ Monit Assess. 2014, 186, 7, and 4637-4646) have studied the different categories of wastes like fruit waste, food waste, yard waste, paper waste, and mixed waste for the biogas production in a laboratory-scale batch digester for a total period of 8 weeks at a temperature of 15-30°C. Thus, the overall process is very slow and energy intensive to be implemented at a large scale.

[0015] WO2014095669 describes a method and plant for producing biogas from lignocellulosic biomass, wherein said process comprises: (a) mixing of the lignocellulosic biomass having an average particle size of less than 200 mm with aqueous solutions at a temperature of 60-100°C and/or with the aid of steam; (b) heating of the lignocellulosic biomass to 130-200°C and maintaining the thus heated lignocellulosic biomass for a duration of 5-120 min; (c) anaerobic fermentation of the thermally treated lignocellulosic biomass by means of microorganisms and recovery of the biogas produced. But the process disclosed in the present disclosure specifies only use of lignocellulosic biomass.

[0016] CN105414158 describes an anaerobic fermentation coupling and hydrothermal liquidation treatment method for kitchen waste. The anaerobic fermentation coupling and hydrothermal liquidation treatment method comprises: pre-treating the kitchen waste; producing oil by carrying out hydrothermal liquidation on pretreated kitchen waste; producing methane, a biogas residue and biogas liquid through anaerobic fermentation; purifying and utilizing multistage products. The present disclosure specifies only the use of kitchen waste. Moreover, the present method has disclosed HRT of 15-20 days for anaerobic fermentation which reduces the overall process productivity.

[0017] To overcome the problems described in the prior art there is need to develop a process for generation of biogas from organic matter which is liquefied by using liquefaction process to produce liquid biocrude which when subjected to well designed AD process yields biomethane in near theoretical yields with improved productivities. Objects of present invention

[0018] The primary object of the present disclosure is to use a continuous, high yield, moderate temperature, pressure, and rapid process for liquefaction of organic matter to produce a liquid biocrude which when subjected to well designed anaerobic digestion (AD) process yields biomethane in near theoretical yields (greater than 90%) and productivities greater than 5.0m³/m³.day with an hydraulic retention time (HRT) of less than 24 h and deploying organic loading rates (OLR) greater than 15 g COD/1, day.

SUMMARY

[0019] In one of the aspects of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain a biocrude; and (b) anaerobic digestion of the biocrude to obtain a biogas.

[0020] These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described. It is to be understood that the present disclosure includes all such variations and modifications. The disclosure also includes all such steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any or more of such steps or features.

Definitions:

[0022] For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are collected here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below.

[0023] The articles "a", "an" and "the" are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

[0024] The terms "comprise" and "comprising" are used in the inclusive, open sense, meaning that additional elements may be included. Throughout this specification, unless the context requires otherwise the word "comprise", and variations, such as "comprises" and "comprising", will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps.

[0025] The term "including" is used to mean "including but not limited to". "Including" and "including but not limited to" are used interchangeably.

[0026] The term "at least one" is used to mean one or more and thus includes individual components as well as mixtures/combinations.

[0027] Ratios, concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or subranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a temperature ranges of about 25-40 C should be interpreted to include not only the explicitly recited limits of about 25 C to about 40 C, but also to include sub-ranges, such as 25-30 C, 28-38 C, and so forth, as well as individual amounts, including fractional amounts, within the specified ranges, such as 25.2 C, and 38.5 ^°C, for example.

[0028] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described. All publications mentioned herein are incorporated herein by reference.

[0029] The present disclosure is not to be limited in scope by the specific implementations described herein, which are intended for the purposes of exemplification only. Functionally- equivalent products, compositions, and methods are clearly within the scope of the disclosure, as described herein. [0030] The term "COD" used herein refers to chemical oxygen demand. Chemical oxygen demand is used to indirectly determine the organic content present in aqueous waste. It is typically given as mg/L of oxygen consumed per liter of aqueous waste.

[0031] The term "organic matter" used herein refers to any organic substance which is discarded after primary use, or it is worthless, defective and of no use. An organic matter is selected from the group but not limited to municipal solid waste, garbage, lignocellulosic biomass, algae, road sweeping, kitchen waste, vegetable waste, cooked food waste, paper waste, garden waste, agriculture and forestry waste etc.

[0032] The term "liquefaction" used herein refers to process in which organic matter is converted into its liquid form. The process may involve thermochemical treatment with catalyst or without catalyst.

[0033] The term "liquid biocrude" used herein refers to carbon rich liquid fraction obtained by liquefaction of organic matter selected from the group but not limited to municipal solid waste, garbage, lignocellulosic biomass, algae, road sweeping, kitchen waste, vegetable waste, cooked food waste, paper waste, garden waste agriculture and forestry waste etc. The obtained liquid biocrude is rich source of fragmented organic compounds, sugars, amino acids, carboxylic acids, phenols, aldehydes, aromatics and micronutrients etc. It is used interchangeably with "biocrude" or "bio-crude" or "bio-crude oil".

[0034] The term "well designed anaerobic digestion" used herein refers to continuous and rapid rate biodigestion process for efficient utilisation of greater than 95% of substrate COD fed for maximum conversion to biomethane in more than 90% of theoretical yield at HRT of less than 24 h in a well controlled and operated digester.

[0035] The term "yield on carbon" used herein refers to the concentration of carbon obtained in liquefied biocrude with respect to the concentration of carbon present in the feed.

[0036] The term "theoretical yield" used herein refers to the stoichiometric amount of biomethane produced per gram COD of liquid biocrude (350 ml CH g COD) at standard temperature & pressure (STP) conditions.

[0037] The term "hydraulic retention time (HRT)" used herein refers to the ratio of digester volume to feed volume added per day and is expressed in hours (h).

[0038] The term "organic loading rates (OLR)" used herein refers to the amount of substrate COD per unit time per volume of digester and is expressed in g COD/1, day [0039] Considering the environmental impact of organic waste, waste management is an important problem. On the other end, the energy-crisis necessitates a strategy to successfully obtain fuel. Anaerobic digestion of waste has typically tackled both these problems by converting waste to fuel. However, known procedures in the art for anaerobic digestion of waste are time consuming, often requiring several days to complete. Hence, the object of the present disclosure is to conveniently convert the organic waste to useful biogas fuel using a process that can be completed within 24 hours and is easy to implement.

[0040] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain a biocrude; and (b) anaerobic digestion of a biocrude to obtain the biogas.

[0041] In an embodiment of the present disclosure there is provided a process as described herein, wherein the productivity of the process is in the range of 5-15 m³ biogas/m³.day.

[0042] In an embodiment of the present disclosure there is provided a process as described herein, wherein the anaerobic digestion of biocrude to obtain biogas is carried out with a hydraulic retention time (HRT) in the range of 18-24 hours.

[0043] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain a biocrude; and (b) anaerobic digestion of the biocrude to obtain a biogas, wherein the productivity of the process is in the range of 5-15 m³ biogas/m³.day.

[0044] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain a biocrude; and (b) anaerobic digestion of the biocrude to obtain a biogas, wherein the anaerobic digestion of biocrude to obtain biogas is carried out with a hydraulic retention in the range of 18-24 hours.

[0045] Another embodiment of the present disclosure provides a process for production of liquid biocrude from organic matter, wherein organic matter used is selected from the group but not limited to municipal solid waste, garbage, lignocellulosic biomass, algae, road sweeping, kitchen waste, vegetable waste, cooked food waste, paper waste, garden waste agriculture and forestry waste, etc.

[0046] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain a biocrude; and (b) anaerobic digestion of the biocrude to obtain a biogas, wherein the liquefaction of organic waste to obtain biocrude comprises the steps of: (a) contacting the organic waste with water to form a first mixture; (b) heating the first mixture to obtain a second mixture; and (c) processing the second mixture to obtain the biocrude.

[0047] In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein the biocrude is obtained as liquid with at least 50% yield on carbon.

[0048] In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein the biocrude has a chemical oxygen demand (COD) in the range of 25-30 g L.

[0049] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain a biocrude; and (b) anaerobic digestion of the biocrude to obtain a biogas, wherein the liquefaction of organic waste to obtain biocrude comprises the steps of: (a) contacting the organic waste with water to form a first mixture; (b) heating the first mixture to obtain a second mixture; and (c) processing the second mixture to obtain the biocrude, and the biocrude is obtained as liquid with at least 50% yield on carbon.

[0050] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain biocrude; and (b) anaerobic digestion of biocrude to obtain biogas, wherein the liquefaction of organic waste to obtain biocrude comprises the steps of: (a) contacting the organic waste with water to form a first mixture; (b) heating the first mixture to obtain a second mixture; and (c) processing the second mixture to obtain the biocrude, and the biocrude has a chemical oxygen demand (COD) in the range of 25-30 g/L.

[0051] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain biocrude; and (b) anaerobic digestion of biocrude to obtain biogas, wherein the liquefaction of organic waste to obtain biocrude comprises the steps of: (a) contacting the organic waste with water to form a first mixture; (b) heating the first mixture to obtain a second mixture; and (c) processing the second mixture to obtain the biocrude, and the first mixture comprises at least 70% water by weight with respect to the first mixture. [0052] In another embodiment of present disclosure there is provided a continuous and rapid AD process for generation of biogas from liquid biocrude, wherein said liquid biocrude comprises fragmented organic compounds, sugars, amino acids, carboxylic acids, phenols, aldehydes, aromatics, micronutrients, and combinations thereof.

[0053] In an embodiment of the present disclosure there is provided a process for generation of biogas from liquid biocrude, wherein liquid biocrude used for AD comprises a biodegradable carbon rich organic fraction obtained after liquefaction. The liquid biocrude is used directly or diluted suitably or treated chemically for biogas production. The process parameters such as but not limited to pH, conductivity, nutrient addition etc. may vary as process obligation.

[0054] In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein processing the second mixture to obtain the biocrude may be carried out by any downstream process such as but not limited to filtration, extraction, distillation and chromatographic separation, membrane separation, selective precipitation, adsorptive separation and combinations thereof.

[0055]In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein heating the first mixture to obtain a second mixture is optionally carried out in the presence of a catalyst selected from the group consisting of transition metals, ionic liquids such as aromatic and aliphatic nitrogen based sulfonic acid ionic liquids, alkali such as alkali metal hydroxides, and carbonates, acids such as Bronsted acids, super acids, and combinations thereof. In another embodiment of the present disclosure, the heating the first mixture to obtain a second mixture is optionally carried out in the presence of an ionic liquid catalyst. In an embodiment of the present disclosure the alkalis are a broad category consisting of sodium hydroxide, potassium hydroxide, and combinations thereof. In an embodiment of the present disclosure the acids are a broad category consisting of selected from the group consisting of hydrochloric acid, sulfuric acid, and combinations thereof. In yet another embodiment of the present disclosure the catalyst is sodium hydroxide. In yet another embodiment of the present disclosure the catalyst is an Imidazole backbone sulfonic acid counter ion Bronsted acid ionic liquid. In yet another embodiment of the present disclosure the catalyst is a Polyethyleneimine (PEI) back bone sulfonic acid counter ion Bronsted acid ionic liquid.

[0056] In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein heating the first mixture to obtain a second mixture is carried out at a temperature in the range of 30-250 °C at a stirring speed in the range of 300-450 rpm for a period in the range of 5-150 min. In another embodiment of the present disclosure, heating the first mixture to obtain a second mixture is carried out at a temperature in the range of 120 °C at a stirring speed in the range of 400 rpm for a period in the range of 120 min. In yet another embodiment of the present disclosure, heating the first mixture to obtain a second mixture is carried out at a temperature in the range of 250 °C at a stirring speed in the range of 400 rpm for a period in the range of 120 min.

[0057] In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein heating the first mixture to obtain a second mixture is optionally carried out under pressure in the range of 5-50 bar.

[0058] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain biocrude; and (b) anaerobic digestion of biocrude to obtain biogas, wherein the liquefaction of organic waste to obtain biocrude comprises the steps of: (a) contacting the organic waste with water to form a first mixture; (b) heating the first mixture to obtain a second mixture is carried out in the presence of an ionic liquid catalyst at a temperature in the range of 120 °C at a stirring speed in the range of 400 rpm for a period in the range of 120 min under a N₂ pressure of 20 bar; and (c) processing the second mixture to obtain the biocrude is carried out by filtration.

[0059] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain biocrude; and (b) anaerobic digestion of biocrude to obtain biogas, wherein the liquefaction of organic waste to obtain biocrude comprises the steps of: (a) contacting the organic waste with water to form a first mixture; (b) heating the first mixture to obtain a second mixture is carried out in the presence of sodium hydroxide at a temperature in the range of 250 °C at a stirring speed in the range of 400 rpm for a period in the range of 120; and (c) processing the second mixture to obtain the biocrude is carried out by filtration

[0060] Another embodiment of the present disclosure provides a process for liquefaction of organic matter for production of liquid biocrude, wherein said liquefaction of said organic matter may be carried out by using methods such as but not limited to catalytic liquefaction (CTL), hydrothermal liquefaction (HTL), catalytic upgrading (CTU), hydrothermal upgrading (HTU), enzymatic treatment, thermochemical treatment etc. [0061] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain biocrude; and (b) anaerobic digestion of biocrude to obtain biogas, wherein the anaerobic digestion of biocrude to obtain biogas comprises the steps of: (a) contacting the biocrude with a microbial consortium to obtain a slurry; and (b) anaerobically digesting the slurry to obtain the biogas.

[0062] In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein the biogas has a minimum biomethane content of 55% (v/v). In another embodiment of the present disclosure the biogas has a minimum biomethane content of 60% (v/v). In yet another embodiment of the present disclosure the biogas has a biomethane content of 80% (v/v).

[0063] In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein the process achieves a conversion of at least 80%. In another embodiment of the present disclosure the process achieves a conversion of at least 90%. In another embodiment of the present disclosure the process achieves a conversion of 95%.

[0064] In present disclosure, the liquid biocrude obtained from liquefaction of organic matter is fed to high rate biodigester for biogas production in near theoretical value (greater than 90%).

[0065] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain biocrude; and (b) anaerobic digestion of biocrude to obtain biogas, wherein the liquefaction of organic waste to obtain biocrude comprises the steps of (a) contacting the organic waste with water to form a first mixture; (b) heating the first mixture to obtain a second mixture; and (c) processing the second mixture to obtain the biocrude and the anaerobic digestion of biocrude to obtain biogas comprises the steps of: (a) contacting the biocrude with a microbial consortium to obtain a slurry; and (b) anaerobically digesting the slurry to obtain the biogas.

[0066] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain biocrude; and (b) anaerobic digestion of biocrude to obtain biogas, wherein the liquefaction of organic waste to obtain biocrude comprises the steps of (a) contacting the organic waste with water to form a first mixture; (b) heating the first mixture to obtain a second mixture; and (c) processing the second mixture to obtain the biocrude and the anaerobic digestion of biocrude to obtain biogas comprises the steps of: (a) contacting the biocrude with a microbial consortium to obtain a slurry; and (b) anaerobically digesting the slurry to obtain the biogas and the biogas has a minimum biomethane content of 55% (v/v).

[0067] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain biocrude; and (b) anaerobic digestion of biocrude to obtain biogas, wherein the liquefaction of organic waste to obtain biocrude comprises the steps of (a) contacting the organic waste with water to form a first mixture; (b) heating the first mixture to obtain a second mixture; and (c) processing the second mixture to obtain the biocrude and the anaerobic digestion of biocrude to obtain biogas comprises the steps of: (a) contacting the biocrude with a microbial consortium to obtain a slurry; and (b) anaerobically digesting the slurry to obtain the biogas and the process achieves a conversion of at least 80%.

[0068] In an embodiment of the present disclosure there is provided a process for production of biogas comprising: (a) liquefaction of organic waste to obtain biocrude; and (b) anaerobic digestion of biocrude to obtain biogas, wherein the liquefaction of organic waste to obtain biocrude comprises the steps of (a) contacting the organic waste with water to form a first mixture; (b) heating the first mixture to obtain a second mixture; and (c) processing the second mixture to obtain the biocrude and the anaerobic digestion of biocrude to obtain biogas comprises the steps of: (a) contacting the biocrude with a microbial consortium to obtain a slurry; and (b) anaerobically digesting the slurry to obtain the biogas and the biogas is produced with a theoretical yield of at least 90%.

[0069] In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein the microbial consortium comprises microorganisms selected from the phylum consisting of Euryarcheota, Firmicutes, Chlorofliexi, Spirochates, Proteobacteria and combinations thereof. The microbial consortium is procured locally and the digester is operated under mesophilic conditions.

[0070] In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein anaerobically digesting the slurry to obtain the biogas is carried out at a temperature in the range of 35-40 °C. In another embodiment of the present disclosure the anaerobically digestion of the slurry to obtain the biogas is carried out at a temperature of 36°C. [0071] In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein contacting the biocrude with a microbial consortium to obtain a slurry is carried out in an anaerobic digester at an organic loading rate in range of 15-25 kg/m³.day.

[0072] In the present disclosure numerous liquefaction strategies have been developed to enhance the reactivity of liquid biocrude and to increase the yield of biogas. Typical goals of liquefaction process include (a) production of amenable and digestible liquid biocrude that enhances biogas yields, (b) avoiding the degradation of sugars, (c) minimizing the formation of inhibitors for subsequent fermentation steps, and (d) cost effective operation and minimize heat and power consumption.

[0073] Yet another embodiment of present disclosure provides a rapid process for generation of biogas from liquid biocrude obtained from liquefaction process, wherein said obtained energy rich liquid biocrude is much more amenable and readily digestible by anaerobic microbial consortia. In an embodiment of the present disclosure the liquefaction of organic waste: a) mimmizes inhibitors selected from the group consisting of long chain fatty acids (C₁₂ to C₂₀), furfural, hydroxyl methyl, furfural, and combinations thereof; and b) produces easily digestible monomers such as hydroxybenzoic acid, benzoic acid, syringic acid, valeric acid, isovaleric acid, acetic acid, propionic acid, xylose, arabinose, glucose etc.

[0074] According to another embodiment of the present disclosure there is provided a high rate AD process for production of biomethane from liquid biocrude using efficient biodigesters, wherein the biodigesters used is selected from the group but not limited to upflow anaerobic sludge blanket (UASB), expanded granular sludge blanket (EGSB), hybrid upflow anaerobic sludge blanket (HUASB), plug flow reactors (PFR), anaerobic fixed bed reactor (AFBR), continuous stirred tank reactor (CSTR) etc. In an embodiment of the present disclosure the biodigester used is CSTR. In another embodiment of the present disclosure the biodigester used is EUASB.

[0075] Another embodiment of the present disclosure provides a process for generation of biogas from liquid biocrude obtained by liquefaction of organic matter, wherein said process may be carried out in continuous mode either single stage or two stages.

[0076] In an embodiment of present disclosure there is provided a process for generation of biogas from liquid biocrude by AD in biodigester, wherein said biodigester comprises of (a) feed inlet and outlet with pumps, (b) gas liquid solid separator (GLSS), (c) gas collection vessel, (d) temperature control unit. The design of biodigester can be modified according to parameters such as but not limited to height, diameter, feed flow rate and temperature etc. and can be varied as per process obligation.

[0077] Another embodiment of present disclosure there is provided a continuous process for generation of biogas from liquid biocrude by anaerobic digestion with high yield, wherein said process is carried out at moderate temperature & pressure. The high rate process for liquefaction of organic matter to produce a liquid biocrude which when subjected to well designed anaerobic digestion (AD) process yields biomethane in near theoretical yields (greater than 90%) and productivities greater than 5.0m³/m³.day with an high retention time (HRT) of less than 24h and deploying organic loading rates (OLR) greater than 15 g COD/1, day.

[0078] One of the embodiments of present disclosure provides a process for generation of biogas from liquid biocrude by anaerobic digestion, wherein said process comprises: a) obtaining liquid biocrude from organic matter in at least 50% yield on carbon by using liquefaction process operated at temperatures below 200°C; b) feeding liquid biocrude obtained from step (a) to anaerobic biodigester at OLRs in excess of 15 g COD/1, day to produce biogas in greater than 90% of theoretical yield and containing at least 55% (v/v) methane, at a productivity greater than 5.0 m³/m³.day resulting in an HRT of less than 24h.

[0079] In most preferred embodiment of present disclosure there is provided a process for generation of biogas from liquid biocrude, wherein said process is carried out by anaerobic digestion (AD). In said AD, liquid biocrude is fed to biodigester at OLRs in excess of 15 g COD/1, day to produce biogas in greater than 90% of theoretical yield and containing at least 55% (v/v) methane at productivity greater than 5.0 m /m .day resulting in an HRT of less than 24h.

[0080] In an embodiment of the present disclosure there is provided a process for production of biogas as described herein, wherein the biogas is used as a fuel in automobile, industrial, electricity generation and agricultural applications.

[0081] The invention is further illustrated by working examples as detailed below. The examples are meant for illustrative purposes only and are not meant imply restriction to the scope of the disclosure in any manner. EXAMPLES

[0082] The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of present disclosure. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the claimed subject matter.

[0083] Several conventional biochemical and thermochemical treatment methods have been studied in prior art to reclaim the energy from MSW. But available conventional methods of treating MSW are inefficient to reclaim the energy from MSW efficiently. In this regard, ionic liquids are dynamic molecules possessing several attractive qualities such as biodegradability, high polarity, ability to dissolve lipophilic molecules and negligible vapor pressure, which mark them out as potential catalysts. A convenient synthetic route to obtain these molecules is discussed below.

[0084] The following paragraphs discuss in detail the process for production of biocrude and the process for obtaining biogas from biocrude. The yield (or theoretical yield) and conversion (or biocrude COD consumption) were calculated using the following formulaic Biocrude COD Consumption (%) = Feed COD (mg/L) -Final COD (mg/l) X 100

Feed COD (mg/l)

Biogas yield (%) = Biogas generation (Litres at NTP)/ day X 100

Biocrude COD (gm) consumed X 0.756 (Litres)

Example 1:

Production of liquid biocrude from market waste by using catalytic liquefaction (CTL) process

[0085] The liquefaction reaction was conducted in batch mode operation in a 100 ml Amar reactor autoclave assembly having four peach bladed ampler and proportional integral device (PID) temperature controller with accuracy ± 1 °C. The autoclave was loaded with 10 gm of crushed market MSW (H₂0 content 70%; first mixture) and blended with ionic liquid catalyst (30% w/w of dry MSW) and then pressurized at 20 bar N₂ pressure and then heated at 120°C for 120 minutes at 400 rpm to obtain the second mixture. The ionic liquid used for the process was Imidazole backbone sulfonic acid counter ion Bronsted acid ionic liquid or Polyethyleneimine (PEI) back bone sulfonic acid counter ion Bronsted acid ionic liquid. After the completion of reaction, the reactor vessel was allowed to cool to room temperature before opening reactor vessel. Sufficient amount of water was added to the reaction mixture followed by vacuum filtration to remove unreacted organic matter to obtain the biocrude. The resulting filtrate was then subjected to COD analysis and the liquid biocrude with 25-30g/L COD was loaded at different OLRs on to biodigester for biomethane production.

Example 2:

Production of liquid biocrude from market waste by using hydrothermal liquefaction (HTL) process

[0086] The liquefaction reaction was conducted in batch mode operation in a 100 ml Amar reactor autoclave assembly having four peach bladed ampler and PID temperature controller with accuracy ± 1 °C. The autoclave was loaded with 10 gm of crushed market MSW (H₂0 content 70%; first mixture) and blended with sodium hydroxide catalyst (20% w/w of dry MSW) and then heated at 250°C for 120 minutes at 400 rpm to obtain the second mixture. After the completion of reaction, the reactor vessel was allowed to cool to room temperature before opening reactor vessel. Sufficient amount of water was added to the reaction mixture followed by vacuum filtration to remove unreacted organic matter to obtain the biocrude. The resulting filtrate was then subjected to COD analysis and the liquid biocrude with 28-30g/L COD was loaded at different OLRs on to biodigester for biomethane production.

Example 3:

Biogas production by anaerobic digestion (AD) using liquid biocrude

[0087] The anaerobic digestion of biocrude to biogas was conducted in continuous mode using both CSTR (5L) and EUASB (2L) type high cell density biodigesters under well optimised operating conditions (different HRTs and OLRs) using acclimatized microbial consortium. The slurry of biocrude and microbial consortium (Schreiber Dynamix Dairies, Pvt. Ltd. Baramati, Maharashtra) was subjected to anaerobic digestion (35-40 °C; OLR of 15-25 g COD/1, day) to obtain the biogas. The microbial consortium comprises microorganisms selected from the phylum consisting of Euryarcheota, Firmicutes, Chlorofliexi, Spirochates, Proteobacteria, and combinations thereof. The COD analysis of digester inflow and outflow was performed to estimate the percentage of substrate utilized and transformed into biogas. The biogas produced was collected in the gas collection vessel and was periodically analyzed for methane composition using GC-TCD (New Chrom, India). Example 4:

Characterization of Biogas

[0088] The Table 1 below provides details of the biogas produced by the method outlined in Examples 3.

Table 1 : Composition of Biogas

[0089] The process as described in present disclosure (outlined in Examples 1-3), relates to a process that allows the convenient conversion of organic waste to economically-viable biogas. As can be seen from Table 1, the obtained biogas is primarily composed of methane (or biomethane). The calorific value of methane is 50-55 MJ/ g and also, methane is well-known to be a green-fuel. Hence, process as described in the present disclosure provides a biogas which is both energy-rich and is environmentally-benign. The said process of the present disclosure is advantageous as it has both high yield (> 90%) and conversion (> 80%) and can be carried out with a HRT of less than 24 hours.

[0090] Although the subject matter has been described in considerable details with reference to certain examples and embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications can be made without departing from the present subject matter as defined.

Claims

I/We Claim:

1. A process for production of biogas comprising :

a) liquefaction of organic waste to obtain a biocrude; and

b) anaerobic digestion of biocrude to obtain biogas.

2. The process for production of biogas as claimed in claim 1, wherein the process has productivity in the range of 5-15 m³ biogas/m³.day.

3. The process for production of biogas as claimed in claim 1, wherein the anaerobic digestion of biocrude to obtain biogas is carried out with a hydraulic retention in the range of 18-24 hours.

4. The process for production of biogas as claimed in claim 1, wherein the organic waste is selected from the group consisting of municipal solid waste, garbage, lignocellulosic biomass, algae, road sweeping, kitchen waste, vegetable waste, cooked food waste, paper waste, garden waste, agriculture waste, forestry waste, and combinations thereof.

5. The process for production of biogas as claimed in any of the claims 1-4, wherein the liquefaction of organic waste to obtain the biocrude comprises the steps of:

a) contacting the organic waste with water to form a first mixture;

b) heating the first mixture to obtain a second mixture; and

c) processing the second mixture to obtain the biocrude.

6. The process for production of biogas as claimed in claim 5, wherein the biocrude is obtained as a liquid with at least 50% yield on carbon.

7. The process for production of biogas as claimed in any of the claims 1-5, wherein the biocrude has a chemical oxygen demand (COD) in the range of 25-30 g/L.

8. The process for production of biogas as claimed in claim 5, wherein the biocrude comprises a compound selected from the group consisting of fragmented organic compounds, sugars, amino acids, carboxylic acids, phenols, aldehydes, aromatics, micronutrients, and combinations thereof.

9. The process for production of biogas as claimed in claim 5, wherein heating the first mixture to obtain the second mixture is optionally carried out in the presence of a catalyst selected from the group consisting of transition metals, ionic liquids, alkali, acids, and combinations thereof.

10. The process for production of biogas as claimed in claim 5, wherein heating the first mixture to obtain a second mixture is carried out at a temperature in the range of 30-250 °C at a stirring speed in the range of 300-450 rpm for a period in the range of 5-150 min.

11. The process for production of biogas as claimed in claim 5, wherein heating the first mixture to obtain a second mixture is optionally carried out under pressure in the range of 5- 50 bar.

12. The process for production of biogas as claimed in claim 5, wherein the liquefaction of organic waste is carried out by a process selected from the group consisting of catalytic liquefaction (CTL), hydrothermal liquefaction (HTL), catalytic upgrading (CTU), hydrothermal upgrading (HTU), enzymatic treatment, thermochemical treatment, and combination thereof.

13. The process for production of the biogas as claimed in any of the claims 1-8, wherein the anaerobic digestion of the biocrude to obtain the biogas comprises the steps of:

a) contacting the biocrude with a microbial consortium to obtain a slurry; and b) anaerobically digesting the slurry to obtain the biogas.

14. The process for production of biogas as claimed in claim 13, wherein the biogas has a minimum biomethane content of 55% (v/v).

15. The process for production of biogas as claimed claim 13, wherein the process achieves a conversion of at least 80%.

16. The process for production of biogas as claimed in claim 13, wherein the biogas is produced with a theoretical yield of at least 90%.

17. The process for production of biogas as claimed in claim 13, wherein the microbial consortium comprises microorganisms selected from the phylum consisting of Euryarcheota, Firmicutes, Chlorofliexi, Spirochates, Proteobacteria, and combinations thereof.

18. The process for production of biogas as claimed in claim 13, wherein anaerobically digesting the slurry to obtain the biogas is carried out at a temperature in the range of 35-40 °C.

19. The process for production of biogas as claimed in claim 13, wherein contacting the biocrude with the microbial consortium to obtain the slurry is carried out in an anaerobic digester at an organic loading rate in range of 15-25 g COD/1, day.

20. The process for production of biogas as claimed in any of the claims 1-19, wherein the liquefaction of organic waste minimizes inhibitors and produces easily digestible monomeric components.

21. The process as claimed in any of the claims 1-19, wherein the biogas is used as a fuel in automobile, industrial, electricity generation, and agricultural applications.