biomethanation of organic waste, anaerobic degradation,degradation of organic waste
TRANSCRIPT
BIOMETHANATION
OF
MUNICIPAL SOLID WASTE
Presented by,
Salin Kumar Sasi
URBAN WASTE SCENARIO
• Urban India generates about 1.4 lakh MT/day of MSW
• Requires 1750 acres of land for land filling/year
Courtesy-MNRE
PHASES
• PHASE I – MSW SCENARIO IN INDIA
• PHASE II – BIOMETHANATION
• PHASE III – FACTORS AFFECTING
BIOMETHANATION
• PHASE IV – BIOMETHANATION PROCESS
• PHASE V – BIOMETHANATION OF MSW IN INDIA
• PHASE VI – BIOMETHANATION PLANT IN
ABROAD AND INDIA
• PHASE VII – RESULTS AND DISCUSSIONS
PHASE I
MSW SCENARIO IN INDIA
Courtesy-MNRE
TECHNOLOGICAL OPTIONS FOR
ENERGY RECOVERY FROM URBAN WASTES
Courtesy-MNRE
Courtesy-MNRE
POTENTIAL OF ENERGY FROM
URBAN WASTES
2007 2017
MSW
(lakh tpd)1.48 2.15 3.03
MW 2550 3670 5200
MLW
(mcd)17.75 20.70 24.75
MW 330 390 460
2012
Courtesy-MNRE
INDIAN SCENARIO
• As per MSW Rule 2000, biodegradable material
should not be deposited in the sanitary landfill
• Therefore there is almost no scope of generation of
biogas in the form of landfill gas from new sanitary
landfills
• However, there is a huge potential of trapping the
landfill gas generated in the old dump-sites across
the country, particularly the large ones with more
than 5 meter thickness (height plus depth)
Courtesy-MNES
Courtesy-NEERI
WTE TECHNOLOGIES
• Bio-methanation
• Incineration
• RDF
• Gasification
• Integrated systems
MERITS OF BIOMETHANATION
• Reduction in land requirement for MSW disposal.
• Preservation of environmental quality.
• Production of stabilized sludge can be used as
soil conditioner in the agricultural field.
• Energy generation which will reduce operational
cost.
• Supplement national actions to achieve real, long
term, measurable and cost effective GHG’s
reductions in accordance with Kyoto Protocol.
PHASE II
BIOMETHANATION
Courtesy-MNRE
PRINCIPLES
• Complex process leading to generation of methane and carbon dioxide.
• Process involves three steps (Barlaz et al 1990) Hydrolysis Acidification Methanogenesis
• Process can be carried out in Single step Two step
HYDROLYSIS
• Anaerobic bacteria breakdown complex organic molecules (proteins, cellulose, lignin and lipids) into soluble monomer molecules such as amino acids, glucose, fatty acids and glycerol.
• Monomers are available to the next group of bacteria.
• Hydrolysis of complex molecules is catalyzed by extra cellular enzymes (cellulose, proteases and lipases).
• Hydrolytic phase is relatively slow ,can be limiting in anaerobic digestion.
ACIDOGENESIS
• Acidogenic bacteria converts sugar, aminoacids and fatty acids to organic acids (acetic, propionic, formic, lactic, butyric acids), alcohols and ketones (ethanol, methanol, glycerol and acetone), acetate, CO2and H2.
• Acetate is the main product of carbohydrate fermentation.
• The products formed vary with type of bacteria as well as with the culture conditions (temperature, pH etc).
ACETOGENESIS
• Acetogenic bacteria converts fatty acids and alcohols into acetate, hydrogen and carbon dioxide .
• Acetogenic bacteria requires low hydrogen for fatty acids conversion .
• Under relatively high hydrogen partial pressure, acetate formation is reduced and the substrate is converted to propionic acid, butyric acid and ethanol rather than methane.
METHANOGENESIS
• Methanogenesis in microbes is a form of anaerobic respiration.
• Methanogens do not use oxygen to breathe, oxygen inhibits the growth of methanogens.
• Terminal electron acceptor in methanogenesis is carbon.
• Two best described pathways involve the use of carbon dioxide and acetic acid as terminal electron acceptors:
CO2+ 4 H2 → CH4 + 2H2O
CH3COOH → CH4 + CO2
Acetate
Short chain fatty acids
Lipase, protease, pectinase
cellulase, amylase produced
by hydrolytic microorganisms
Stage 1 Hydrolysis
Organic matter
(Carbohydrates, lipids, proteins etc)
Stage 2 Acidogenesis
(mainly acetic and formic acid)Stage 3 Acetogenesis
Acetate CO2 and H2
Methane +CO2
ß-oxidation, glycolysis
deamination, ring reduction
and ring cleavage
Carboxylic volatile acids, keto acids,
hyroxy acids, ketones, alcohols,
simple sugars, amino aicds,H2 and CO2
Stage 4 Methanogenesis
Courtesy-Kashyap .D.R et al ,2003
PHASE - III
FACTORS AFFECTING
BIOMETHANATION
Courtesy-MNRE
NUTRIENTS
• Lower nutrient requirement compared to aerobic bacteria.
• COD:N range is 700:5.
• N used in synthesis of Enzymes, RNA, DNA.
• Concentration of various nutrients (Speece et. al ,1996)
N : 50 mg/lP : 10 mg/lS : 5 mg/l
pH
• Most important process control parameter.
• Optimum pH between 6.7 & 7.4 range for methanogenic bacteria (Zehnder et. al. 1982).
• Excess alkalinity or ability to control pH must be present to guard against the accumulation of excess volatile acids.
• The three major sources of the alkalinity are lime, Sodium bicarbonate and sodium hydroxide.
TEMPERATURE
• Constant and Uniform temperature maintenance.
• Three temperature range
Psychrophilic range ; < 200 C.
Mesopholic range ; 200 C to 400C.
Thermophilic range ; >400 C.
• Rates of methane production double for each 100C temperature change in the mesophilic range .
• Loading rates must decrease as temperature decreases to maintain the same extent of treatment.
• Operation in the thermophilic range is not practical because of the high heating energy requirement (Ronald L. Drostle – 1997)
• Study of temperature variation (Alvarez Rene et al 2007).
Forced square-wave temperature variations
(i) 11 0 C and 25 0 C,
(ii) 15 0 C and 29 0 C,
(iii) 19 0 C and 32 0C.
Large cyclic variations in the rate of gas production
and the methane content.
The values for volumetric biogas production rate and
methane yield increased at higher temperatures.
The average volumetric biogas production rate for
cyclic operation between 11 and 25 0C was 0.22 L d -1 L -
1 with a yield of 0.07 m 3CH 4kg -1 VS added (VSadd)
Between 15 and 29 0C the volumetric biogas
production rate increased by 25% (to 0.27 L d -1L-1with
a yield of 0.08 m 3CH 4 kg -1 VSadd).
Between 19 and 32 0C, 7% in biogas production was
found and the methane yield was 0.089 m3 CH4 kg-1
VSadd.
Digester showed an immediate response when the
temperature was elevated, which indicates a well-
maintained metabolic capacity of the methanogenic
bacteria during the period of low temperature.
Periodic temperature variations appear to give less
decrease in process performance than as prior
anticipated.
Courtesy- Alvarez Rene et al 2007
SOLID RETENTION TIME (SRT) AND
HYDRAULIC RETENTION TIME(HRT)
• SRT is defined as the average time the solid particles
remains in the reactor.
• The anaerobic digestion is typically performed in
Continuously Stirred Tank Reactor (CSTR).
• The performance of CSTR is dependent on hydraulic
retention time (HRT) of the substrate and the degree of
contact between the incoming substrate and a viable
bacterial population (Karim et al.,2005).
• An increase or decrease in SRT results in an increase or
decrease of the reaction extent.
MIXING
• Mixing creates a homogeneous substrate preventing
stratification and formation of a surface crust, and
ensures solids remain in suspension.
• Mixing enables heat transfer and particle size reduction
as digestion progresses .
• Mixing can be performed in two different ways(Kaparaju
P et al,2007):
Continuous mixing – SRT is equal to HRT
Non-continuous mixing – SRT is more than HRT
• The effect of continuous , minimal (mixing for 10 min
prior to extraction / feeding) and intermittent mixing
(withholding mixing for 2 hr prior to extraction/feeding)
on methane production was investigated in lab-scale
CSTR (kaparaju P. et. al ,2007) .
• On comparison to continuous mixing, intermittent and
minimal mixing strategies improved methane
productions by 1.3% and 12.5%, respectively.
ALKALINITY
• Calcium, magnesium, and ammonium
bicarbonate are examples of buffering substances
found in a digester .
• A well established digester has a total alkalinity
of 2000 to 5000 mg/L.
• The principal consumer of alkalinity in a reactor
is carbon dioxide .
TOXICITY
• Toxicity depends upon the nature of the substance
, concentration and acclimatization .
• NH 4-N concentration of 1500-3000 mg/L at 200C
and pH 7.4 and above is considered stimulatory .
• Anaerobic process is highly sensitive to toxicants
due to slow growth rate.
PHASE-IV
BIOMETHANATION PROCESS
Courtesy-MNRE
BIOMETHANATION INCLUDES FOUR
MAJOR ELEMENTS
1. Pretreatment.
2. Digestion.
3. Gas purification
4. Residue treatment.
PRETREATMENT
• Separate out inorganic matter and materials which disrupt mechanical operation of the digester
• Increase the biodegradability of the substrate.
• Classification of the refuse by either wet or dry separation processes
• Provides the feedstock with a high concentration of digestible matter, relatively free of metals, glass and grit
• Dry separation processes offer the advantage of flexibility in selecting the desired water content
• Wet separation processes operate at low solids concentrations, and have the disadvantage of requiring a dewatering step
DIGESTION
• Organic feedstock is mixed with nutrients and control chemicals.
• Lime and ferrous salts are added for pH and hydrogen sulfide control.
• Digester operates at mesophilic conditions ( 370C ).
• The conversion occurs in two steps firstly solids are solubilized or digested by enzymic action, secondly the soluble products are fermented in a series of reactions resulting in the production of methane and carbon dioxide.
PRODUCTS OF DIGESTION
• Consist of two streams
The gas stream is composed of approximately equal
volumes of methane and carbon dioxide.
The slurry stream is composed of an aqueous
suspension of undigested organic matter.
SINGLE-STAGE HIGH RATE
DIGESTION
• Process done in single digester
• Uniform feed is very important
• Digester fed on daily cycle of 8 or 24 hours.
• Digester tank may have fixed roof or floating
roof.
TWO-STAGE DIGESTION
• Seldom used in modern digester design.
• High rate digester coupled with second tank in
series.
• Second tank not provided with mixing
contraption.
• Less than 10% of the gas generated comes from
second tank
GAS TREATMENT AND HANDLING
• Gas from digester contains methane, carbon dioxide and trace quantities of hydrogen sulfide.
• CO2 and H2S must be removed if the methane gas is to be pumped for combustion purpose.
• Standard method of removing acid gases from natural gas is by absorption with monoethanolamine (MEA), the MEA is then regenerated and recirculated.
• Methane must also be dried, accomplished by a glycol dehydration process in which the moisture is absorbed in dry glycol, which is also regenerated and recirculated.
PHASE V
BIOMETHANATION OF MSW IN
INDIA
Project for generation of 5 MW power from Municipal Solid
Waste at Lucknow (Courtesy MNRE)
Courtesy-MNRE
ENERGY RECOVERY POTENTIAL
Courtesy-Ambulkar.A.R et al 2003
Energy ResourcesMaterial Resources
Commercial
sources
Non-conventional
sources
Industrial
Utilization
Agricultural
Consumption
Human
Consumption
Waste Generation
Manure
Biomethanation
TechnologyBiogas
Processing
of waste
Degradable
organic matterInerts
Municipal
Solid waste
Energy Generation-Consumption in System
Role of Biomethanation Technology
in the system
Energy ResourcesEnergy ResourcesMaterial ResourcesMaterial Resources
Commercial
sources
Commercial
sources
Non-conventional
sources
Non-conventional
sources
Industrial
Utilization
Industrial
Utilization
Agricultural
Consumption
Agricultural
Consumption
Human
Consumption
Human
Consumption
Waste GenerationWaste Generation
ManureManure
Biomethanation
Technology
Biomethanation
TechnologyBiogasBiogas
Processing
of waste
Processing
of waste
Degradable
organic matter
Degradable
organic matterInertsInerts
Municipal
Solid waste
Municipal
Solid waste
Energy Generation-Consumption in System
Role of Biomethanation Technology
in the system
ENERGY GENERATION/CONSUMPTION IN
SYSTEM
Courtesy-Ambulkar.A.R et al 2003
Parameters related with Technical
Feasibility
Need for obtaining waste
with desired composition
addressing the following
issues:
• Annual seasonal
variation in waste
composition.
• Identification of
points for collection
of waste.
• Source specific
collection of waste.
Ensuring process kinetics
to be fast enough for
implementation at plant
scale addressing the
following parameters with
optimum conditions:
• pH
• Digester Temperature
(Thermophilic,
mesophilic conditions)
• Carbon to Nitrogen ratio
• Maintenance of
COD/BOD values of the
reactor feed.
Ensuring the
conditioning of waste
at processing site with
respect to the
following points:
• Removal of non-
biodegradables
• Removal of
binders like soil
particles, stones,
etc.
• Adjustment of
water content in
the feed to the
reactor.
Parameters related with Technical
Feasibility
Parameters related with Technical
Feasibility
Need for obtaining waste
with desired composition
addressing the following
issues:
• Annual seasonal
variation in waste
composition.
• Identification of
points for collection
of waste.
• Source specific
collection of waste.
Need for obtaining waste
with desired composition
addressing the following
issues:
• Annual seasonal
variation in waste
composition.
• Identification of
points for collection
of waste.
• Source specific
collection of waste.
Ensuring process kinetics
to be fast enough for
implementation at plant
scale addressing the
following parameters with
optimum conditions:
• pH
• Digester Temperature
(Thermophilic,
mesophilic conditions)
• Carbon to Nitrogen ratio
• Maintenance of
COD/BOD values of the
reactor feed.
Ensuring process kinetics
to be fast enough for
implementation at plant
scale addressing the
following parameters with
optimum conditions:
• pH
• Digester Temperature
(Thermophilic,
mesophilic conditions)
• Carbon to Nitrogen ratio
• Maintenance of
COD/BOD values of the
reactor feed.
Ensuring the
conditioning of waste
at processing site with
respect to the
following points:
• Removal of non-
biodegradables
• Removal of
binders like soil
particles, stones,
etc.
• Adjustment of
water content in
the feed to the
reactor.
Ensuring the
conditioning of waste
at processing site with
respect to the
following points:
• Removal of non-
biodegradables
• Removal of
binders like soil
particles, stones,
etc.
• Adjustment of
water content in
the feed to the
reactor.
PARAMETERS RESPONSIBLE FOR TECHNICAL
FEASIBILITY OF BIOMETHANATION PLANT
Courtesy-Ambulkar.A.R et al 2003
Factors affecting the
economy of plant
Compromise with the
quality of raw material as
energy generation
source
•MSW being a
heterogeneous
mixture has a
remarkable seasonal
variation which
hampers the quality
of product
Energy inefficiency associated
with the plant
• Biological processing is a time
consuming process and hence
energy generation rates are
low.
• Net energy generation rate is
low as it involves the
efficiencies associated with
both biogas generation and
biogas combustion.
• The calorific value of biogas is
comparatively less as it
contains about 50% CO2 along
with methane.
Costs associated with
Pre- and Post- treatment
of the feed
• Raw material being a
heterogeneous
mixture with
considerable amount
of inerts and needs
pre-treatment.
• Large amount of
wastewater is
generated with
needs an efficient
method for treatment.
Problems associated with
marketing of products
• Uncertainty in markets
for the digestate
represents a
commercial risk, which
impacts on the
technology’s costs.
• Other energy
generation sources
will have to competitive
edge over the biogas.
• Compost is not yet
established as a
product marketable.
Factors affecting the
economy of plant
Factors affecting the
economy of plant
Compromise with the
quality of raw material as
energy generation
source
•MSW being a
heterogeneous
mixture has a
remarkable seasonal
variation which
hampers the quality
of product
Compromise with the
quality of raw material as
energy generation
source
•MSW being a
heterogeneous
mixture has a
remarkable seasonal
variation which
hampers the quality
of product
Energy inefficiency associated
with the plant
• Biological processing is a time
consuming process and hence
energy generation rates are
low.
• Net energy generation rate is
low as it involves the
efficiencies associated with
both biogas generation and
biogas combustion.
• The calorific value of biogas is
comparatively less as it
contains about 50% CO2 along
with methane.
Energy inefficiency associated
with the plant
• Biological processing is a time
consuming process and hence
energy generation rates are
low.
• Net energy generation rate is
low as it involves the
efficiencies associated with
both biogas generation and
biogas combustion.
• The calorific value of biogas is
comparatively less as it
contains about 50% CO2 along
with methane.
Costs associated with
Pre- and Post- treatment
of the feed
• Raw material being a
heterogeneous
mixture with
considerable amount
of inerts and needs
pre-treatment.
• Large amount of
wastewater is
generated with
needs an efficient
method for treatment.
Costs associated with
Pre- and Post- treatment
of the feed
• Raw material being a
heterogeneous
mixture with
considerable amount
of inerts and needs
pre-treatment.
• Large amount of
wastewater is
generated with
needs an efficient
method for treatment.
Problems associated with
marketing of products
• Uncertainty in markets
for the digestate
represents a
commercial risk, which
impacts on the
technology’s costs.
• Other energy
generation sources
will have to competitive
edge over the biogas.
• Compost is not yet
established as a
product marketable.
Problems associated with
marketing of products
• Uncertainty in markets
for the digestate
represents a
commercial risk, which
impacts on the
technology’s costs.
• Other energy
generation sources
will have to competitive
edge over the biogas.
• Compost is not yet
established as a
product marketable.
PARAMETERS AFFECTING THE COMMERCIAL
VIABILITY OF BIOMETHANATION PLANT
Courtesy-Ambulkar.A.R et al 2003
Factors enhancing the
economy of plant
Reduction in costs
• Reduction in raw
material transportation
cost.
• The feed MSW is very
cheap and so less raw
material cost.
Financial Incentives from
government
• Financial and fiscal
incentives offered by the
Ministry of Non
Conventional Energy
Sources.
• Constitutional Amendment
Act and emphasis on
privatization has led to the
creation of this market in
India.
Factors enhancing the
economy of plant
Factors enhancing the
economy of plant
Reduction in costs
• Reduction in raw
material transportation
cost.
• The feed MSW is very
cheap and so less raw
material cost.
Reduction in costs
• Reduction in raw
material transportation
cost.
• The feed MSW is very
cheap and so less raw
material cost.
Financial Incentives from
government
• Financial and fiscal
incentives offered by the
Ministry of Non
Conventional Energy
Sources.
• Constitutional Amendment
Act and emphasis on
privatization has led to the
creation of this market in
India.
Financial Incentives from
government
• Financial and fiscal
incentives offered by the
Ministry of Non
Conventional Energy
Sources.
• Constitutional Amendment
Act and emphasis on
privatization has led to the
creation of this market in
India.
PARAMETERS FAVORING THE COMMERCIAL
VIABILITY OF BIOMETHANATION PLANT
Courtesy-Ambulkar.A.R et al 2003
PHASE VI
BIOMETHANATION PLANT IN
ABROAD AND INDIA
VALORGATM PLANT AT FRANCE
• PrincipleThe Valorga process is an anaerobic biological treatment process for waste organic fraction .
• Advantages
Adapted to the treatment of organic municipal solid waste
The process operates under anaerobic conditions with a high dry solid content of 25 - 35 %, owing to a specific process design.
Anaerobic digestion leads to the production of a high methane content gas: the biogas.
Does not require a large land area.
VALORGATM PROCESS
SPRERI PLANT AT ANAND Courtesy- SPRERI
SPRERI PLANT AT ANAND
SARDAR PATEL RENEWABLE ENERGY RESEARCH INSTITUTE
APPROPRIATE RURAL TECHNOLOGY
INSTITUTE (ARTI), PUNE
Schematic description of the small ARTI compact
biogas plant. Courtesy-ARTI
APPROPRIATE RURAL TECHNOLOGY INSTITUTE
(ARTI), PUNE
Construction of an ARTI compact
biogas plant.
ARTI biogas plant for treatment of
kitchen waste at household level.
The design, has won the Ashden Award for Sustainable Energy 2006
Bhabha Atomic Research Centre (BARC), Mumbai
Courtesy-MNES
Biogas Plant at Trombay
Courtesy-MNES
Parameters of BARC technology
Courtesy-MNES
The Energy and Resources Institute (TERI), New Delhi
Courtesy-TERI
Waste is fed into the acidification module. UASB unit
The Energy and Resources Institute (TERI), New Delhi
Courtesy-TERI
PROJECTS INSTALLED FOR
ENERGY FROM URBAN WASTES
• 6.6 MW project based on MSW at Hyderabad
• 6 MW project based on MSW at Vijayawada
• 5 MW project based on MSW at Lucknow
• 1 MW power from Cattle Dung at Ludhiana
• 150 kW plant for Veg. Market, sewage and
slaughterhouse waste at Vijayawada
• 250 kW power from Veg. Market wastes at
Chennai.
PHASE VII
RESULTS ANS DISCUSSIONS
SALIENT POINTS
ULTIMATE GOAL OF BIOMETHANATION
DEVELOPMENT OF NATIONAL POLICY
DEVELOPMENT OF APPROPRIATE TECHNOLOGY
IMPROVEMENTS IN COLLECTION AND
TRANSPORTATION SYSTEMS
MARKETING STRATEGY
ALLOCATION OF FUNDING
PUBLIC AWARENESS
CONCLUSION
Considerable potential for enhancing the biogas
production from the present stock of MSW
generated in the country.
Drastic reduction in the emission of CH4 and
CO2, earning the country precious carbon credits.
Assist in implementation of KYOTO protocol.
REFERENCES
Alvarez Rene and Liden Gunnar (2007), ‘The effect of temperature variation on biomethanation’, Bioresource Technology 99 (2008) pp 7278- 7284.
Ambulkar A.R and Shekdar A.V (2003), ‘Prospects of biomethanation technology in the Indian context: a pragmatic approach’, Resources Conservation and Recycling 40 (2004) pp 111-128.
Bhattacharyya J.K., Kumar S., Devotta S., (2008), ‘Studies on acidification in two-phase biomethanation process of municipal solid waste’, Waste Management 28 (1), 164-169. Bioresource Technology 77 (2000) pp 612-623.
Dhussa A. K and Tiwari R.C (2000), Article on Waste-to-energy in India.http://www.undp.org.in/programme/GEF/march00/page 12-14.
Kaparaju P, Buendia I, Ellegaard L and Angelidakia I (2007), ‘Effect of mixing on methane production during Thermophilic anaerobic digestion of manure: Lab-scale and pilot-scale studies’, Bioresource Technology 99 (2008) pp 4919-4928.
Karim K., Hoffmann R., Klasson K.T., Al-Dahhan M.H.,(2005), ‘Anaerobic digestion of animal waste : effect of mixing’, Science Technology 45, pp 3397-3606.
Kashyap. D.R, Dadhich. K. S, Sharma. S. K (2003), ‘Biomethanation under psychrophilic conditions’, Bioresource Technology 87 (2003) pp 147 - 153.
Kim I.S., Kim D.H., Hyun S.H.,(2002), ‘Effect of particle size and sodium concentration on anaerobic thermophilic food waste digestion’, Science Technology 41,pp 61-73.
Kumar D., Khare M., Alappat B.J.(2001), ‘Leachate generation from municipal landfills in New Delhi, India’.27th WEDC Conference on People and Systems for Water, Sanitation and Health, Lusaka, Zambia.
Mahindrakar AB, Shekdar AV.(2000), ‘ Health risks from open dumps: a perspective’, Bioresource Technology 63 (2000) pp 281 - 293.
Muller Christian., (2007), ‘Anaerobic digestion of biodegradable solid waste in Low and Middle income countries’, Eawag Aquatic Research.
Municipal Solid Waste (Management and Handling) Rules,(2000), MNES, Govt of India, New Delhi.
NEERI Report (2005), ‘Assessment of Status of Municipal Solid Waste Management in Metro Cities, State Capitals, Class I Cities and Class II Towns’.
Parkin G. F,Owen, William F, (1986)*, ‘ Fundamentals of anaerobic digestion of waste water sludges’, J. Env. Engg. Div. ASCE, Vol. 112, No. 5, pp 867-920.
Ronald, L. Drostle, (1997)*, ‘Theory and practice of water and waste water treatment’, John Wiley and sons, Inc USA ( NewYork).
Sawyer, Clair N, Mc Carty, Perry L. and Gene F. Parkin (2003), ‘Chemistry for Environmental Engineering and Sciences (Fifth Edition), Tata McGraw Hill Book Company, pp 689-697.
Solid waste manual (2004), MNES, Govt of India.
Speece R.E. (1983)*, ‘Anaerobic biotechnology for Industrial waste water treatment’. Env. Sci.and Tech Vol.17, No.19, pp 416A.
Vavilin V.A., Angelidaki I., (2005), ‘Anaerobic degradation of solid material: Importance of initiation centers for methanogenesis, mixing intensity and 2D distributed model’, Biotechnology, Bioengineering 89(1), 13-122.
Zehnder, A.J, K. Ingvorsen and T. Marti (1982)*, ‘ Microbiology of methanogen bacteria in anaerobic digestion’, pp 45-68.
* - Papers not referred in original
WISHING A VERY HAPPY
TEACHER’S DAY