Review article Analysis of different techniques used for improvement of biomethanation process: A review Meena Krishania ⇑ , Virendra Kumar, Virendra Kumar Vijay, Anushree Malik Center for Rural Development and Technology, Indian Institute of Technology Delhi, New Delhi 110 016, India article info Article history: Received 21 September 2011 Received in revised form 24 August 2012 Accepted 2 December 2012 Available online 25 December 2012 Keywords: Biomethanation Biofuel Biomass Pretreatment Bioenergy abstract Biomethanation process is a promising eco-friendly solution for the treatment of organic biomass which leads to efficient bioenergy production. However, this technology is necessary to clarify the best opera- tional conditions and suitable reactors for treating the target substrates in order to make the technology assessable to rural areas. Present review is dedicated to focus the various techniques, which can be used to solve the constraints occurring during the gas production and help to enhance gas production. Brief description of possible pretreatments for converting complex lignocellulosic waste to biogas and desired range of operational parameters which are required to enhance the anaerobic digestion are discussed. Further suitable reactors for different substrates have also been analyzed. Ó 2012 Elsevier Ltd. All rights reserved. Contents 1. Introduction ........................................................................................................... 2 2. Feedstocks for biomethanation systems ..................................................................................... 2 3. Pretreatment for biomethanation systems ................................................................................... 3 3.1. Alkali pre-treatment ............................................................................................... 3 3.2. Thermochemical pre-treatment ...................................................................................... 3 3.3. Milling .......................................................................................................... 4 3.4. Additives and nutrients............................................................................................. 4 4. Optimization of operational parameters for biomethanation .................................................................... 4 4.1. Temperature ..................................................................................................... 4 4.2. pH.............................................................................................................. 4 4.3. Fatty acids ....................................................................................................... 4 4.4. Solid concentration ................................................................................................ 4 4.5. Hydraulic Retention Time (HRT) ..................................................................................... 4 4.6. C:N ratio......................................................................................................... 5 4.7. Mixing .......................................................................................................... 5 4.8. Microbial biomass ................................................................................................. 5 4.9. Reactor designing ................................................................................................. 5 5. Socio-economic and environmental benefits of digesters ....................................................................... 6 6. Conclusion ............................................................................................................ 7 References ............................................................................................................ 8 0016-2361/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.fuel.2012.12.007 ⇑ Corresponding author. Tel.: +91 11 26596351; fax: +91 11 26591121. E-mail address: [email protected](M. Krishania). Fuel 106 (2013) 1–9 Contents lists available at SciVerse ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel
Transcript
Fuel 106 (2013) 1–9
Contents lists available at SciVerse ScienceDirect
Fuel
journal homepage: www.elsevier .com/locate / fuel
Review article
Analysis of different techniques used for improvement of biomethanation process:A review
Meena Krishania ⇑, Virendra Kumar, Virendra Kumar Vijay, Anushree MalikCenter for Rural Development and Technology, Indian Institute of Technology Delhi, New Delhi 110 016, India
a r t i c l e i n f o a b s t r a c t
Article history:Received 21 September 2011Received in revised form 24 August 2012Accepted 2 December 2012Available online 25 December 2012
Biomethanation process is a promising eco-friendly solution for the treatment of organic biomass whichleads to efficient bioenergy production. However, this technology is necessary to clarify the best opera-tional conditions and suitable reactors for treating the target substrates in order to make the technologyassessable to rural areas. Present review is dedicated to focus the various techniques, which can be usedto solve the constraints occurring during the gas production and help to enhance gas production. Briefdescription of possible pretreatments for converting complex lignocellulosic waste to biogas and desiredrange of operational parameters which are required to enhance the anaerobic digestion are discussed.Further suitable reactors for different substrates have also been analyzed.
As the fossil fuel resources are very limited and their demand ishigh, the gap can be met with the energy generation from renew-able resources. One of the feasible renewable energy for India isfrom biomass as biomass availability in the country is very high– 150 million MT per annum [1].
From ancient time, biomass has always been a good source ofenergy for mankind and it contribute around 14% of the world’s en-ergy supply [2]. In India 80% of the total energy consumed in ruralareas comes from biomass fuels such as fire wood, crop residues,live stock dung [1], municipal solid waste, algae, industrial wasteand agricultural residues which are easily available in abundance.Traditionally biomass has been utilized for cooking through directcombustion in cookstoves (chullahs) producing dust which isharmful for health. Presently agriculture residue usage is limitedto the production of producer gas in which burning process ruinsthe equally important fertilizer and compost value of biomass.There are several methods of conversion of biomass to energy[3]. Biofuels are feasible way to utilize lignocellulosic materialsfor fuel (Fig. 1). Among several technologies the anaerobic diges-tion technology has proved to be viable and promising technology.Recent life cycle assessment studies have demonstrated that bio-gas derived methane (biomethane) is one of the most energy effi-cient and environmentally sustainable vehicle fuel. At the sametime, nutrients contained in the remaining digestate can be usedfor crop production and play a remarkable role in promoting sus-tainable biomass production systems.
A production of biofuels from biomass can contributes in reduc-ing the greenhouse emissions and hence slows down the climatechange. Asian countries, it is estimated that 17,730 Gg of CH4,1,290,000 Gg of CO2 and 179 Gg of N2O are emitted from animalwastes. Using the biogas that can be produced from recoverableanimal wastes as a substitute for fuel such as kerosene in cookingwill reduce net GHG emissions by 53.1%, 19.5% and 61.1% for CH4,CO2 and N2O, respectively [4]. Among several renewable technolo-gies the biomethanation technology is a commercially proventechnology and is widely used for treating biomass. India has builtabout 4 million family sized biogas plants in past [5].
In recent times biomethanation technology has become moreattractive source of renewable energy due to reduced technologicalcost and process efficiency. Different variety of substrates such as
waste water, animal waste, industrial waste, municipal solidwaste, agricultural residues, energy crops [6] and water based re-source like algae [7] are extensively used in this anaerobic technol-ogy. Methane production through biomethanation technology hasbeen evaluated as one of the most energy-efficient and environ-mentally benign way of producing vehicle biofuels and can providemultiple benefits to the users.
In biomethanation process the organic waste is converted intoenergy (methane) and enriched manure by consortium of microorganism’s action in the absence of air, also known as anaerobicdigestion [7]. The important processes in anaerobic digestion arehydrolysis, acidogenesis, acetogenesis, and methanogensis, wherehydrolysis step is an extra cellular process where the hydrolyticand acidogenic bacteria excrete enzyme to catalyze hydrolysis ofcomplex organic materials into smaller units. The hydrolyzed sub-strates are then utilized by acidogenic bacteria. Product such as ace-tate, hydrogen and carbon dioxide can directly be used bymethanogenic bacteria producing methane and carbon dioxide,while other more products such as alcohol and volatile fatty acidsare further oxidized by acetogenic bacteria in syntrophic with themethanogens [8]. The whole process is carried out with the helpof microorganisms and the growth of microorganisms depends onvarious parameters like pH, temperature, C/N ratio, organic loadingrate, reactor designing, inoculums and HRT [9]. Therefore, to harnessfully the anaerobic digestion potential, these parameters should bemaintained in the optimized range. Pre-treatment, additives andreactor designing according to feedstock can solve the major limita-tions like low gas production from agricultural residues, largehydraulic retention time and low gas production in winters [9].
This review paper explores the methane potential of varioussubstrates along with their essential properties. There is specificfocus on anaerobic degradation of lignified biomass with the helpof pretreatment which ensures the complete harnessing of the en-ergy and fertilizer aspect of biomass. Fundamental requirement ofthe optimization of operating parameters is discussed with majorconstraints. Further suitable reactors for substrates have been ana-lyzed in the paper.
2. Feedstocks for biomethanation systems
Feedstock could also be used as the organic waste containingprotein, fats, or carbohydrate cellulose which with the help of
Table 1Feedstocks for biogas production [10,11].
Feedstocks Total waste (fresh) Gas yield (m3/kg of dry matter) Pretreatment requirement Reference
Waste (kg/day/head)Cattle 10–15 0.34 No [10,11]Poultry 0.75 0.46 No [10,14]Sheep 0.75 0.37 No [10,15]Pig 1.3 0.39 Yes [10,16]Night Soil 0.75 0.38 No [10,17]Kitchen 0.25 0.30 Yes [10,22]
microbes can be converted into biomethane energy. The organicwastes for digestion can be classified into three categories i.e. solid,semi-solid and liquid [10]. Solid waste resources contains energycrops, agricultural residues, de oiled seed cakes, weeds, spoilt fod-der, leaves, urban solid waste, etc. Semi Solid waste resources [1]-cattle, sheep, goat and pig wastes (dung and meat), fishery wastes,poultry wastes, slaughter house waste and human waste, aquaticwaste (sea weeds, marine algae, water hyacinth), etc. Liquid wasteresources [10] like distilleries, dairy plants, pulp and paper indus-tries, poultry industries, sugar industries, food processing industry,etc. Table 1 shows the daily availability of the selected feedstockswhich can be used for bio methane production.
There are several organic wastes available in India but agricul-tural waste and crop residue has the highest contribution [1]. Agri-cultural residues are good source for anaerobic digestion due tolarge availability of biomass. Agricultural residues contains 15–20% lignin and C/N ratio varies from 130 to 150 [3]. Because ofthese complex characteristics and properties, agricultural residuesneed pre-treatment and additives to enhance the biogas produc-tion. Some of feedstocks need treatment and some are naturallygood for biomethanation [11]. Table 2 shows the properties ofsome lignocellulosic materials.
3. Pretreatment for biomethanation systems
Agricultural residues or lignocellulosic biomass is the mostabundant renewable resource with the potential of conversion tobiofuels. An agricultural residue contains high percentage of ligno-celluloses, which is hardly biodegradable by anaerobic bacteria.Biological and chemical pre-treatment have proved to be promis-ing methods to improve biogas production from lignocellulosicbiomass [12]. Pre-treatment is aim at the improvement of anaero-bic digestion efficiency and the choice of suitable reactors makesthe process even more efficient [13,23]. There are several pretreat-ments for lignocellulosic materials, some of effective pretreat-ments are briefly explained below.
3.1. Alkali pre-treatment
Alkali pre-treatment is done with NaOH (sodium hydroxide),Ca(OH)2 (lime) or ammonia to remove lignin. This process helps
to make a part of the hemicelluloses and cellulose accessible toenzymes. NaOH is found to be the best and capable enough toincrease biogas production by approximate 16.6% [30–32].Furthermore, treatment of the sludge with dilute NaOH (e.g.1.6 g/l) at room or low temperature (25–35 �C) helps to improvethe volatile solids (VS) removal by 40–90% [33]. A similar treat-ment by 5 g/kg NaOH on municipal solid waste has been reportedto improve the formation of biogas by 35% [34]. Alkaline pre-treat-ment proved to be more effective on agricultural residues than onwoody materials [35]. Sulfuric acid lignin (SAL) could be easily dis-solved in an alkaline medium, especially sodium hydroxide solu-tion at neutral pH [36]. In steam explosion, pre-treatment ofwheat straw it is first treated with steam at 200–220 �C and 15–22 bar. Then the residue is delignified by 2% H2O2 at 50 �C for 5 hat pH 11.5 [37]. The steam explosion pre-treatment results in a sig-nificant loss of hemicelluloses, and about 11–12% lignin removal,while the alkaline peroxide post-treatment results in 81–88% re-moval of the original lignin, which altogether removes 92–99% ofthe original lignin from wheat straw [38].
3.2. Thermochemical pre-treatment
Acid treatment of lignocellulosic materials at a high tempera-ture can efficiently enhance the enzymatic hydrolysis. Sulfuric acidis the most applied acid, while other acids such as Hydrochloricacid and Nitric acid can also be used. Dilute-acid pre-treatmentcan be performed either for short retention time (e.g. 5 min) athigh temperature (e.g. 180 �C) or for a relatively longer retentiontime (e.g. 30–90 min) at lower temperatures (e.g. 120 �C) [33].Dilute-acid hydrolysis is the most commonly applied methodamongst the chemical pre-treatment methods. At temperature(e.g. 140–190 �C) and low concentration of acid (e.g. 0.1–1% sulfu-ric acid), the dilute-acid treatment can achieve high reaction ratesand significantly improve cellulose hydrolysis. Almost 100% hemi-cellulose removal is possible by dilute-acid pretreatment. Diluteacid pre-treatment can disrupt lignin and increases the cellulose’ssusceptibility to enzymatic hydrolysis, but it not effective in dis-solving lignin [37]. Thermo chemical pre-treatment of chickenmanure with NaOH and H2SO4 at 100 �C was found to increaseboth methane yield and biodegradability [38]. Pre-treatment by
4 M. Krishania et al. / Fuel 106 (2013) 1–9
microwave/alkali/H2O2 had the highest hydrolysis rate and highestglucose content comparing to other chemical pretreatments [39].
3.3. Milling
Milling can improve susceptibility to enzymatic hydrolysis byreducing the size of the material, and degree of crystallinity oflignocelluloses. This helps in improving enzymatic degradation ofthese materials towards biogas production [33]. Methane yield in-creases with decreasing in particle size. Biogas production fromrice straw with combination of grinding, heating, and ammoniatreatment (2%) results in the highest biogas yield [11]. In anotherstudy, grinding of municipal solid waste from 2.2 to 1.1 mm hadno effect on mesophilic digestion, but improved thermophilicdigestion by 14% [33].
3.4. Additives and nutrients
For the growth and survival of microorganism and for efficientbiogas production nutrients are required. Essential nutrient re-quired for proper anaerobic digestion should have the ratio ofC:N:P:S = 600:15:5:1 for sufficient biogas production [7]. Manytrace elements are very important to develop biofilm in reactor likeFe, Zn, Cu, Ni and Co. Fe (5 mg/l), Zn (1 mg/l), Cu 0.1 (mg/l), Ni(1.2 mg/l) and Co (4.8 mg/l), have been reported to improve thebiomethanation process [11]. Addition of nickel can increase ace-tate utilization rate of methane forming bacteria as F430 enzymein the bacteria contains nickel [39]. For optimal growth the bacte-rial cells need cobalt to buildup the Co-containing corroid factor III.For digestion of agricultural residues, addition of micronutrientand macronutrients are absolutely necessary. Besides these ele-ments, some substrates also enhance the biogas production andits composition. Addition of pectin to cattle dung slurry increasesthe biogas yield. It not only enhances biogas but also impart pro-cess stability during period of fluctuating temperature [40].
Addition of 5% commercial charcoal to cow dung slurry on dryweight basis raised the yield 17–35% [41]. Addition of inert mate-rials like vermiculite, bagasse, gulmohar leaves, wheat straw,ground nut shells and lugiminous plants leaves increase the biogasyield, gas composition and extent of biodegradation [3].
4. Optimization of operational parameters for biomethanation
4.1. Temperature
Optimized range of temperature; thermophilic is 50–60 �C,mesophilic is 32–35 �C and psychophilic is up to 20 �C (As VS deg-radation is less in low temperature, psychophilic bacteria producesgas at very low rate) [42]. Small variation in temperature of diges-ter affects the biological activity of anaerobic bacteria thus reduc-ing the rate of gas production [43]. However, HRT depends on thetemperature. Constant temperature is important for preventingnegative effects on biogas production. Wood chips degrades morerapidly at 55 �C (thermophilic temperature, 11 days it degradescompletely whereas at 38 �C it degrades completely in 20 days)[44]. Most of methanogenic microorganisms are mesophilic andvery sensitive to thermal temperature. The growth rate of microbesis higher at thermophilic temperature; the process becomes faster,more efficient and reduces more HRT than the mesophilic. Thethermophilic temperatures also result in imbalance and high riskfor ammonia inhibition. Increase in temperature also increasesammonia toxicity [7,45]. Some options to increase the heatingwithin the reactors in rural areas are passive solar heating, under-ground digester and combination of both. Digesters with black
coating adsorb heat and none insulating material for digesters helpto maintain the temperature.
4.2. pH
Biomethanation process takes place in a relatively narrow pHrange, from 6.5 to 8.5 [23]. pH is necessary to be in desired rangebecause it directly affects the growth of microbes. The optimalpH of methanogensis is around pH 7.0, the optimum pH of hydro-lysis and acidogenesis has been reported as between 5.5 and 6.5[33]. This variation in pH makes biomethanation process workeffectively in two stage process-hydrolysis/acidogenesis and ace-togensis/methanogensis separately [23]. The pH value increasesby ammonia accumulation during degradation of protein, whileaccumulation of VFA (volatile fatty acid), resulting from degrada-tion of organic matter (1 g of volatile acids produces per gram ofvolatile solids) [46] decreases the pH value. pH below 6.6 is toxicto methanogenisis [47], it is important to maintain pH in desiredrange for efficient gas production [48]. pH can be maintained bycalcium hydroxide (1 g/l).
4.3. Fatty acids
VFA’s (acetic acid, propionic acid and butyric acid) are key inter-mediate in the biomethanation process which are capable of inhib-iting methanogensis at high concentration [7]. Pullammanappallilet al. [49] reported the digester failure when the concentration ofacidic acid and propionic acid reached above 3000 mg/l. Sudden in-crease in organic loading rate is expected to cause an accumulationof high VFA’s, since acetogens grow at a slower rate and subse-quently a significant drop in pH occurs. High VFA inhibits growthof acid producing bacteria thus reducing rate of acidogensis. Fer-mentation of sugar is inhibited by total VFA concentrations above4 g/l [50,51]. Formation of volatile fatty acids from fats/lipids andammonia from proteins beyond a particular range inhibit themethane production [51–53].
4.4. Solid concentration
The degradable part of feed material in a unit volume of slurry isdefined as solid concentration. The total solids (TS) concentrationof the waste influences the pH, temperature and effectiveness ofthe microorganisms in the decomposition process. The solid con-centration is optimized according to the reactor design. Normally7–9% solid concentration is best suited for floating dome reactors[9,54]. The CSTR was simulated over a range of % TS concentrationof 4–10, at a maximum fractional conversion of 0.8 to cater for sys-tem inefficiencies [55]. Table 3 shows the % TS in feedstock’s forbiomethanation. It is found that the highest gas production fromdairy manure is 15.2% TS [1]. High organic loading rate (OLR) re-duce the HRT and capital cost generated by size of digesters [56].
4.5. Hydraulic Retention Time (HRT)
Most anaerobic systems are designed to retain the waste for afixed number of days. Number of days the materials stays in thetank is called the Hydraulic Retention Time or HRT [57]. TheHydraulic Retention Time is equal to the volume of the tank di-vided by the daily flow, HRT = Volume (V)/Flow (Q). In tropicalcountries like India, HRT varies from 30 to 50 days and is depen-dent on the weather conditions [58]. HRT is important since itestablishes the quantity of time available for bacterial growthand subsequent conversion of the organic material to gas. TheHRT vary with the feedstocks, concentration of solids and temper-ature. Increase in temperature reduces the HRT of substrate into
Table 3The total solid content and C/N ratio of some common organic materials [10,11,56].
Materials Dry matter content (%) Water content (%) C/N ratio
CSTR Cattle Dung 0.5 m3/m3/d 35 37 9.2 [73]Agricultural waste 0.29 m3/kg COD 20 55 1.9(COD) [13]Industrial water 0.66–1.47 m3/m3/d 1 30 N. A. [74]
UASB Agricultural waste 0.267 m3/kg COD 20 55 2.8(COD) [13]Food waste 25 l/g VS 16 35 4.5 [76]Industrial water 0.1 m3/kg COD 0.6 atm. T – [79]
M. Krishania et al. / Fuel 106 (2013) 1–9 5
the digesters. Table 4 shows the variation in HRT with temperatureand substrates concentration.
4.6. C:N ratio
The C/N (carbon to nitrogen) ratio in the feedstock is veryimportant because high level of nitrogen (>80 mg/l) as undisso-ciate ammonia (at low C/N ratio) can cause toxicity, while low levelof nitrogen (at high C/N ratio) can inhibit the rate of digestion. It isnecessary to maintain proper C/N ratio of substrate in desiredrange. It has been established that during biomethanation processmicroorganisms utilize carbon 25–30 times more than nitrogen[9]. C/N ratio also can be optimized according to the type of reactor,the two-stage reactor has been reported as reliable process with C/N ratios less than 20 [59]. The Co-digestion of different compatiblesubstrate can also be used to maintain the C/N ratios. Table 3shows the C/N ratios of different organic wastes.
4.7. Mixing
Mixing is a physical operation which creates uniformities in flu-ids and eliminates any concentration and temperature gradients.The main aim of stirring the digester contents is to provide an inti-mate contact between micro organisms and substrate for enhanc-ing the biomethanation process. Mixing doesn’t always take placecontinuously because excessive mixing can reduce biogas produc-tion. It is reported that slow mixing allow the digester to better ab-sorb the disturbance of shock loading than high mixing of thereactor contents [59]. Excessive mixing can disrupt the granules(microbial biomass) structure; reduce the rate of oxidation of fattyacids which can lead to digester instability [60,61]. A survey con-ducted by the German Federal Agricultural Research Centre(2006) observed 60% of anaerobic digesters installed operate sub-mersible mixers. 40% paddle, long shaft, central mixers or a combi-nation of them. A study carried out by the University of Natural
Resources and Applied Life Sciences, Vienna revealed average mix-ing times of 3–4 h per day. 10–20 rpm is suitable for high solidcontents.
As a first estimate the overall daily power consumption can becalculated as such:
Daily energy consumption ðkW hÞ¼ number of mixers � 3—4 h � power input ðkWÞ:
4.8. Microbial biomass
During the degradation of waste within an anaerobic digester,facultative anaerobic bacteria like Enterobacter spp., produce avariety of acids and alcohols, carbon dioxide and hydrogen fromcarbohydrates, lipids and proteins [46]. Anaerobes are active in ab-sence of oxygen and some anaerobes are strong acid producer,such as, Streptococcus spp. [52]. In anaerobic digestion, strict anaer-obes, methanogens are used to convert the acetate, alcohol, carbondioxide and hydrogen into methane by methane forming bacterialike Methanobacterium, Methanococcus, etc. For efficient degrada-tion of waste in biomethanation specific group of micro organismsare necessary [62]. Anaerobes survive and degrade substrate mostefficiently when the oxidation–reduction potential (ORP) of theirenvironment is between 200 and 400 mV (millivolt) [46]. Microbialflora of anaerobic digestion was analyzed and found that, the 185bacteria and 25 Eukaryota phylotypes were have closest sequencedata [63]. In Anaerobic digestion nearly 90% of the archaeal and60% of the bacterial species-level diversity in digesters [64].
4.9. Reactor designing
Various digester configurations are employed using differentapproaches such as one-stage or two-stage digesters, wet or dry/semi-dry digesters, batch or continuous digesters [65], attached
Fig. 2. Showing different types of common biogas reactors in India (a) laboratory batch reactor, (b) fixed Dome reactor, (c) floating dome reactor, (d) continues stirrer tankreactor (CSTR), (e) plug flow and, (f) up flow anaerobic sludge blanket (UASB) [8,48,68].
6 M. Krishania et al. / Fuel 106 (2013) 1–9
or non-attached biomass digesters, high-rate digesters and digest-ers with combination of different approaches [66]. The gas produc-tion varies considerably with time, and several units must beoperated simultaneously to maintain a constant gas supply [10].The fermentation works out normally with solid content (6–10%TS) known as wet fermentation and at high concentration (morethan 20%) known as dry fermentation. [67] have reported thatthe fermentation can proceed at TS concentrations up to 32%.Choice of reactor type is determined according to waste character-ization, particularly by solid contents. High total solid substratesare mainly treated in continuous flow stirred tank reactors (CSTRs),while soluble organic waste are treated using high rate biofilm sys-tems such as up flow anaerobic sludge blanket (UASB) reactors[13]. Fig. 2 shows the different types of bioreactors used for biogasproduction from different wastes. CSTR and Plug flow reactors arebest for agricultural residues [48,13]. Table 4 lists the suitabledigesters for the different substrates. Table 5 some examples ofsuccessfully running biomethanation projects in India.
5. Socio-economic and environmental benefits of digesters
Biogas production covers around 60% of fuel needs for cooking,leading to 50–60% decrease in firewood consumption (i.e. defores-tation) and greenhouse gases emissions; while the annual incomeis increased by 3–5.5% due to fertilizer saving as shown in Table 6[81]. The use of traditional fuels produces smoke and particulatethat pollute the environment and causes several respiratory dis-eases. The biogas provides a clean fuel that helps reducing air pol-lution and no respiratory diseases. However the H2S content is indesired limit. In developing countries, like China and India, the bio-gas generated in household digesters meets all cooking fuel needs;sometimes it is even used for lighting, breeding, heating water orelectricity generation. Which sources of energy have been usedso far and to what extent they can be replaced must be determinedfor the economic evaluation of biogas by means of calorific valuerelations. The monetary benefits of biogas depend mainly on howfar commercial fuels can be replaced and their respective price
Table 5Some examples of successfully running biomethanation projects in India [80].
States (India) Capacity Year
Andhra Pradesh1. Biogas plant based on Starch Industry Wastes at Vensa Biotek, Samalkot, A.P. 0.70 MW 1999–
20002. Biogas generation project based on liquid abattoir waste at M/s Alkabeer Exports Ltd., Medak, A.P. 0.25 MW 1997–983. Biogas based power generation project by M/s Sri Sarvaraya Sugars Ltd. at Chelluru Village, East Godavari Distt., A.P. 1.00 MW 2006–074. Biogas based power generation project by M/s Tern Distilleries (P)Ltd., Tallapalam Village, Visakhapatanam, A.P. 0.75 MW 2006–07
Gujarat1. Biogas based power project at Kanoria Chemicals & Industries Ltd., Ankleshwar, Gujarat 2.00 MW 1998–992. Starch industry waste based biogas to power (through 100% biogas engine) project by M/s Sayaji Industry Ltd., Ahmedabad, Gujarat,
Ahmedabad,1.00 MW 2008–09
Karnataka1. Biogas based power project at Ugar Sugar Works, Bel gaum, Karnataka 1.00 MW 1999–
20002. Starch industry waste based biomethanation project by M/s Riddhi Siddhi Gluco Boils Pvt. Ltd., Gokak, Karnataka 2.00 MW 2007–08
Madhya Pradesh1. Biogas based power project at Som Distilleries Ltd., Raisen, M.P. 2.7 MW 1999–
20002. Tannery liquid waste based biomethanation project by M/s Bhopal Gelatines Pvt. Ltd., Jinsi, Bhopal 0.08 MW 2008–09
Maharashtra1. Biogas based Power Generation Project at Brihan Sugar Syndicate Ltd., Sheerpur, Dist. Solapur, Maharashtra 1.00 MW 2000–012. Seafood industry waste based biomethanation project by M/s Gadre Marine Export Pvt. Ltd., Ratnagiri, Maharashtra 0.86 MW 2006–073. Biogas based power project with 100% biogas engine by M/s Tilak Nagar Distilleries, Ahmednagar 0.694 MW 2008–09
Punjab1. Biogas generation project for Paper Mill black liquor at Satia Paper Mills, Muktsar, Punjab 0.75 MW 1997–982. Biogas waste based power project by M/s Chandigarh Distillers and Bottlers Ltd., Banur, Dist. Patiala, Punjab 8.25 MW 2007–08
Tamil Nadu1. Biogas generation project for paper mill effluents at Tamil Nadu Newsprints and Papers Ltd., Karur, TN 1.25 MW 2002–032. Biogas based power project with 100% biogas engine by M/s Trichi Distillers & Chemicals Ltd., Senthannipuram, Tiruchirapalli 1.40 MW 2008–093. Tapioca Starch Industry Liquid waste based biomethanation project by M/s Spac Tapioca Products (India) Ltd., Poonachi Bhavani TK ,
Erode, Tamilnadu1.00 MW 2008–09
Uttar Pradesh1. Biogas based power generation project at Saraya Distilleries, Gorakhpur, U.P. 2.00 MW 2002–032. Food industry waste based biomethanation project by M/s Saf Yeast Co. Pvt. Ltd., 101, UPSIDC, Industrial Area, Sandila, Distt. Hardoi, U.P. 0.73 MW 2006–07
Uttarakhand1. Starch industry liquid waste based biomethanation project by M/s Riddhi Siddhi Gluco Biols, Udham Singh Nagar, Uttarakhand 1.52 MW 2007–08
Present research is mainly focusing on renewable energy likebiomethane production from the large available biomasses (ligno-cellulosic). Inclusion of highly lignified biomass for production ofbiogas is necessary to meet energy requirement. In present
8 M. Krishania et al. / Fuel 106 (2013) 1–9
scenario agriculture residue usage is limited to the production ofproducer gas in which burning process ruins the equally importantfertilizer and compost value of biomass. Degradation of lignifiedbiomass is difficult but it could be done through pre-treatment,adding additives and suitable reactor designing which can alsosolve the major limitations like low gas production from agricul-tural residues in winters and large hydraulic retention time.Further, optimization of all operating parameters like pH, Temper-ature, C/N ratio, HRT and inoculums help to fully harness the bio-methanation technology and maximizing the production ofbiomethane per unit of biomass.
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