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TERI Information Monitor on Environmental Science 3(2): 67–75

Anaerobic digestion technologies for energyrecovery from industrial wastewater - a study inIndian context

Arun Kansal, K V Rajeshwari,Malini Balakrishnan,Kusum Lata, V V N KishoreTERIDarbari Seth BlockHabitat Place, Lodhi RoadNew Delhi - 110 003

Anaerobic digestion of biodegradable waste results in both energy genera-tion and reduction of greenhouse gas emissions. It would not only replacethe use of fossil fuels in various applications but would also utilize methanegenerated from the waste. In spite of the fact that there is significant poten-tial of energy generation from industrial wastewater in India, the technol-ogy is yet to be fully established. This work reviews the current status inanaerobic treatment technology and examines the various reactor typessuitable for treatment of wastewater. The problems associated with theimplementation of anaerobic digestion in selected industrial sectors arealso discussed. Finally, the programmes initiated by the Government ofIndia to promote the technology are reviewed.

IntroductionThe generation and disposal of large quantities of biode-gradable waste without adequate treatment results insignificant environmental pollution. Besides health re-lated problems for the population near the sites wherewaste is dumped, further degradation of waste in theenvironment can lead to the release of greenhouse gases(GHGs) such as methane and carbon dioxide. In the ab-sence of any waste treatment, as is normally the case,the environmental damage costs to the society works outto be more than the financial costs to the industry. Someof the waste streams are treated by conventional meanslike aeration which is both energy intensive and expen-sive, and generates a significant quantity of biologicalsludge which must then be disposed of. In this context,anaerobic digestion offers potential energy savings andis a more stable process for medium and high strengthorganic effluents. Apart from treating the wastewater,the methane produced from the anaerobic system can berecovered. Besides reducing the amount of GHGs bycontrolled use of methane from waste, the substitutionof oil and coal with bioenergy will result in saving theglobal environment by reducing the use of fossil fuels.

An increasing realization of the potential of anaerobictreatment is evident from the large number of recent re-search publications on this process. Till the late 1960s,aerobic processes were very popular for biologicaltreatment of waste. The energy crisis in the early 1970s,coupled with increasingly stringent pollution controlregulations, brought about a significant change in themethodology of waste treatment. Energy conservationin industrial processes became a major concern and

anaerobic processes rapidly emerged as an acceptablealternative. This led to the development of a range ofreactor designs suitable for the treatment of low, me-dium, and high strength wastewater.

The anaerobic process has several advantages overthe other available methods of waste treatment. Mostsignificantly, it is able to accommodate relatively highrates of organic loading. With increasing use of anaero-bic technology for treating various process streams, it isexpected that industries would become more economi-cally competitive because of their more judicious use ofnatural resources. Therefore, anaerobic digestion tech-nology is almost certainly assured of increased usage inthe future.

The aim of this paper is to assess the current status inanaerobic treatment technology and suggest ways toadopt anaerobic digestion for wastewater treatment.This work also covers the problems associated with theimplementation of anaerobic digestion technology andfuture course of action in the Indian context in the lightof current legislation and relevant standards of dis-charge.

Sources of pollutionIndia is bestowed with abundant water resources. How-ever, large-scale abstraction in the upper stretches andincreased human and industrial activities along thebanks have rendered most of the Indian rivers vulner-able to pollution and health hazards and made them unfitfor designated use. Water resources are polluted by var-ied sources, the most critical of which are city sewageand industrial waste discharge. Sewage contributes

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about 60% of the total pollution load in terms of bio-chemical oxygen demand (BOD). In the industrial sec-tor, water pollution is caused by a few industrialsub-sectors which release toxic wastes and organic pol-lutants. Total wastewater generation from major waterconsuming industries such as agro-based industries, re-fineries, petrochemicals, fertilizers, and industrialchemicals was estimated to be about 3000 million litresper day (mld) in 1997 (TERI 1998). Almost 65%–70% ofthe organic pollutants released in the water bodies in thecountry are accounted for by food and agro-product in-dustries such as distilleries, sugar factories, and pulpand paper mills. Table 1 gives the share of industrialoutput to water pollution in India while Table 2 summa-rizes the characteristics of wastewater which is gener-ated from various agro-based industries.

The Central Pollution Control Board (CPCB) has se-lected 17 categories of major polluting industries forpriority action. The status of pollution control in theseindustries is shown in Table 3. More than 50% of theunits in four categories, namely, distillery, pulp andpaper, textiles, and iron and steel are yet to attain satis-factory performance levels with regard to installation

Table 1. Share of different industries in water pollu-tion in India

Industry Share in terms ofBOD (%)

Industrial chemicals 29Iron and steel 0Non-ferrous metals 10Other chemicals 1Food products 38Paper and pulp products 19Non-metallic mineral products 0Petroleum refineries 2Textiles 1

Source. World Bank (1996)

Table 2. Wastewater characteristics of various sectors of industries

Description Distillery Sugar Pulp and paper Dairy Edible oil Coffee

Wastewatergeneration 12–16 m3/m3 0.2–1.8 m3/tonne 230 m3/tonne 3 m3/m3 57 m3/tonne 5 m3/tonne

(per unit product)COD (mg/l) 90 000–110 000 1800–3200 5908 1120–3360 3200–6000 2800BOD (mg/l) 35 000–50 000 720–1500 1800 320–1750 NA 1510PH 4.0–5 4–7 7–9 5.6–8 5–10 5–5.5TS (mg/l) 8000–120 000 3500 8 831 NA NA NATSS (mg/l) NA NA NA 68–240 NA 311Oil and grease (mg/l) NA NA NA 68–240 400 NA

Note. COD—chemical oxygen demand; TS—total solids; TSS—total suspended solids; NA—not available

Table 3. Pollution control systems in major pollutingindustries

Category of industry Total units Industrieswith ETP (%)

Caustic soda 13 92Cement 253 55Dairy 127 69Distilleries 218 50Fertilizers 108 69General engineering 851 78Integrated iron and steel 237 34Inorganic chemicals 442 8Man-made fibre 16 75Mining 77 44Oil drilling 15 73Pulp and paper 279 32Pesticide 70 73Petrochemical 67 36Pharmaceutical 256 80Refinery 26 50Rubber products 118 64Sugar 393 74Tannery 85 62Textile 559 44Thermal power 87 70

Source. CPCB (1997)

and operation of effluent treatment plants (ETP) andemission control systems.

Development of anaerobic treatmentsystemsAnaerobic digestion of biodegradable wastes involves alarge spectrum of bacteria of which three main groupsare distinguishable.1. The first group comprises fermenting bacteria

which perform hydrolysis and acidogenesis. Thisinvolves the action of exo-enzymes to hydrolysepolymeric matter like proteins, fats, and carbohy-drates into smaller units which can then enter the

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cells to undergo an oxidation-reduction process re-sulting in the formation of volatile fatty acids(VFA) and some carbon dioxide and hydrogen. Thefermenting bacteria are usually designated as acidi-fying or acidogenic population because they pro-duce VFA.

2. Acetogenic bacteria constitute the second group andare responsible for breaking down the products ofthe acidification step to form acetate. In addition,hydrogen and carbon dioxide (in the case of oddnumbered carbon compounds) are also producedduring acetogenesis.

3. The third group involves methanogenic bacteriawhich convert acetate or carbon dioxide and hydrogeninto methane. Other possible methanogenic substrateslike formate, methanol, carbon monoxide, and methy-lamines are of minor importance in most anaerobic di-gestion processes.

In addition to these three main groups, hydrogen con-suming acetogenic bacteria are always present in smallnumbers in an anaerobic digester. They produce acetatefrom carbon dioxide and hydrogen and, therefore, com-pete for hydrogen with the methanogenic bacteria. Also,the synthesis of propionate from acetate, as well as pro-duction of longer chain VFA, occurs to a limited extentin anaerobic digestion. Competition for hydrogen canalso be expected from sulphate reducing bacteria in thecase of sulphate containing wastes (DeZeeuw 1986).

It was a long accepted belief that anaerobic digestionwas feasible only for the treatment of concentratedwastes such as manure and sewage sludge with long re-tention times (Table 4). Around 1950, anaerobic treat-ment of wastewater was attempted and the concept ofhigh rate systems received importance with the use ofmixing devices. The latter helped to break scum in thedigester and increase contact between organisms and thesubstrate. Special reactor types for wastewater treat-ment such as the anaerobic contact processes were alsodeveloped. The energy crisis in 1973 greatly increasedthe interest in anaerobic digestion for all biodegradablewastewater. Advanced methods such as the upflowanaerobic sludge blanket (UASB) process and variousfixed film reactor types based on the principle of sludgeimmobilization were introduced at this point. Atpresent, anaerobic digestion is a popular option and is awidely used wastewater treatment method.

Anaerobic reactors for wastewatertreatmentConventional digesters such as sludge and anaerobiccontinuous stirred tank reactors (CSTR) have been usedin India for many decades in sewage treatment plants forstabilization of the activated sludge and sewage solids.

The area is well researched and sufficient informationand operating experience is therefore available on thesubject. In recent times, the emphasis has shifted to highrate biomethanation systems which are based on theconcept of sludge immobilization techniques (UASB,fixed films, etc). Details of these reactors are given inthe following paragraphs.

Fixed film reactorIn stationary fixed film reactors (Figure 1), cells aredeliberately attached to large sized solid support. Thereactor has a biofilm support structure (media) for bio-mass immobilization, wastewater distribution systemfor uniform distribution of wastewater above/below themedia, and effluent draw off and recycle facilities (ifrequired). The fixed film reactors offer distinct advan-tages such as simplicity of construction, elimination ofmechanical mixing, better stability at higher loadingrates, and capability to withstand large toxic shock loads(van den Berg et al. 1985). In addition, these reactorscan tolerate sudden organic shock loads at constant

Table 4. Historical developments in anaerobic treat-ment technology

Investigator Process description

M Louis Mouras (1881) Mouras-Automatic ScavengerWD Scot-Moncrieff The first application of an anaerobic

(1880) England filterDonald Cameron Septic tank

(1883) EnglandAt Matunga Waste disposal tanks at leper colony

Bombay (1897) with gas collectorsHarry W Chark Sludge was formed in a separate

(1899) USA tankWilliam O Travis Travis tank with hydrolysing

(1904) chamberKarl Imhoff (1905) Modification of Travis tankGermany (1927) The first sludge heating apparatus

in a separate digestion tank was setup. The collected gas was deliveredto municipal gas system.

Fair and Moore (1930) Importance of seeding and pHcontrol

Morgan and Torpey Mixing in digester and development(1950) of high rate digestion

Stander (1950) Development of Clarigester andanaerobic baffled reactor based onrotating biological contacter (RBC)concepts

Young and McCarty Anaerobic filter(1969)

Lettinga (1979) UASB Switzenbum and Developed the further concept of

Jewell (1980) anaerobic filters to fixed filmreactors

Source. Khanna (1989)

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hydraulic loading and recover normal performancewithin a few days if the alkalinity is high enough tomaintain the pH above 6.2 (Kennedy, Droste 1985). Thereactors can process different waste streams with littlecompromise in capacity and can adapt readily to changes intemperature. This is important for installations wherewastewater characteristics change rapidly. The reactorstart-up can be very quick after a period of starvation (oneor two days to reach maximum capacity after three weeksof starvation) (van den Berg et al. 1985).

The main limitation of this design is that the reactorvolume is relatively high compared to other high rateprocesses due to the volume of the media. Another com-mon problem associated with stationary fixed film reac-tors is clogging due to non-uniform growth of biofilmthickness and/or high suspended solids concentration inthe wastewater. Non-uniform growth and consequentclogging occurs especially at the influent entry (van denBerg et al. 1985). Some measures to combat this prob-lem include recirculation of effluent and gas for devel-oping a relatively thin film and sloughing of biomass;provision for relatively thin layer of media near the loadentering area to accumulate the excess biofilm; and im-provement in the flow distribution system to avoid verylow liquid velocity.

Activated carbon, polyvinyl chloride (PVC) supports,hard rock particles, and ceramic rings are the varioustypes of film support which have been tried. Reactorconfiguration and operation (upflow or downflow modeof operation) have a marked effect on performance ofthe reactor (van den Berg et al. 1985). With wastes con-taining large amounts of hard-to-digest suspended sol-ids, recirculation aids in degradation since it keeps thesolids in suspension (Kennedy, van den Berg 1982).

Figure 1. Schematic diagram of fixed bed reactor

Upflow anaerobic sludge blanket reactorUASB technology is being used extensively for a largenumber of different types of industrial effluents. Thesystem uses sludge granules as a means of achievinghigh mean cell residence time (MCRT) thereby achiev-ing highly cost effective designs. UASB processes havefound a variety of applications in recent years in thetreatment of high strength and low/medium strengthwastewater and a variety of other substrates. The pro-cess has been applied to wastewater generated from awide cross-section of industries such as distilleries,food processing units, tanneries, etc., in addition tomunicipal wastewater. A major advantage is that thetechnology has less investment requirements comparedto an anaerobic filter or a fluidized bed system. Notabledisadvantages include (i) long start-up period, (ii) re-quires sufficient amount of granular seed sludge forfaster start-up, and (iii) significant wash-out of sludgeduring the initial phase of the process.

A UASB reactor (Figure 2) essentially consists of agas–solids separator (to retain the anaerobic sludgewithin the reactor), an influent distribution system, andeffluent draw off facilities. With a sophisticated feed dis-tribution system installed in a UASB reactor, effluentrecycle (to fluidize the sludge bed) is not necessary as suf-ficient contact between wastewater and sludge is guaran-teed even at low organic loads (Kaul, Nandy 1998).

Figure 2. Schematic diagram of UASB reactor

Gas

Effluent

FeedFeed

EffluentGas solidseparator

Gas baffle

Influent

Sludgebed zone

Sludgeblanket zone

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Anaerobic fluidized bed treatmentIn the anaerobic fluidized bed (Figure 3), the media forbacterial attachment and growth is kept in the fluidizedstate through application of high upflow velocities, nor-mally achieved by recycling the effluent. Increasing re-cycling allows the process to tend towards theoperational characteristics of a completely mixed sys-tem. The design of a fluidized bed thus consists of awastewater distributor, a media support structure, me-dia, head space, effluent draw off, and recycle facili-ties. The thickness of the biofilm is controlled by thebed regeneration and by the size and density of the inertmedia in combination with the upflow velocity. Excesssludge can be removed from the top of the fluidized bedwhere the biofilm tends to have the maximum thickness.

Fluidized bed technology is more effective thananaerobic filter technology as it favours the transport ofmicrobial cells from the bulk to the surface and thusenhances the contact between the micro-organisms andthe substrate (Perez et al. 1998). These reactors haveseveral advantages over anaerobic filters. They are lesslikely to clog and have a low hydraulic head loss com-bined with better hydraulic circulation (Collivingnarelliet al. 1991). They are able to operate at lower requiredretention times and/or higher loading rates (Perez et al.1998) and have a greater surface area per unit of reactorvolume. Finally, the capital cost is lower due to reducedreactor volumes. However, the recycling of effluentmay be necessary to achieve bed expansion. Thus, thestationary packed bed technology is adequate for thetreatment of easily biodegradable wastewater or where

Figure 3. Schematic diagram of anaerobic fluidized bed sys-tem

high COD removal is not required, while the fluidizedbed technology is especially suitable for treatment ofhazardous wastes with recalcitrant compositions (Perezet al. 1998).

Hybrid reactorThe hybrid reactor (Figure 4) is an improved version ofthe UASB system and combines the merits of the upflowsludge blanket and fixed film reactors. This reactor of-fers strong resistance to disturbances such as large fluc-tuations in loading rate. As most of the microbes adherefirmly to the support media, any change in fermentationconditions would only temporarily affect the microbes.Even at a very high upflow velocity of effluent, thebiofilm is not washed away.

A successful phase separation (in terms of acidogenicand methanogenic phases) can be achieved with thistype of design. Thus, not only does the hybrid reactorprovide the best environment for the growth of both theorganisms (acidogens and methanogens), it also over-comes the limitations normally experienced with theUASB system.

The hybrid reactor can be used for a wide variety ofindustrial effluents and it is possible to maintain the de-sired pH conditions for both the acidogens and themethanogens. The inert matrix material increases theretention of the granular sludge and prevents the wash-out of the microbial population. By choosing a suitablehighly porous packing material with a large specific sur-face, the adhesion of microbes can be greatly improvedand the concentration of activated sludge in the reactorscan be considerably enhanced. The rate of mass transferis also higher owing to the increased contact time be-tween the feed and the microbes. As the material whichimmobilizes the microbes can capture most of the

Figure 4. Schematic diagram of hybrid reactor

Gas

Fluidizedsludgebed

Effluent

FeedFeed

Gas Gas

Sludge bed

Effluent

Anaerobicfilter

Feed

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sludge when the slurry passes through the reactor, theloss of sludge is minimized. Apart from the advantagesof simplicity in operation and design, the hybrid reactoralso works out to be more economical than fixed bedsystem at the industrial scale.

Anaerobic treatment systems in India –current statusConsidering the overall deterioration of the quality ofwater resources, it is of utmost importance to find con-sistent long-term solutions. In the recent past, there hasbeen an exponential growth in the application of anaero-bic technology, both for municipal and industrial waste-water treatment. The most widely used designs havebeen the UASB, fixed film, and expanded fluidized bedreactors. A 0.4 mld capacity sewage treatment plantbased on fixed film reactor has been installed at theRegional Research Laboratory, Bhubaneshwar under theUnited Nations Development Programme–Global Envi-ronment Facility (UNDP–GEF) assisted programme.Apart from small-scale demonstrations, a number offull-scale treatment units are also being built, several ofthem under various river action plans. The world’s firstfull-scale UASB demonstration plant for municipalwastewater was built in Kanpur, Uttar Pradesh in 1989under the Indo–Dutch Project and has been in operationsince then. The plant is designed to treat 5 mld domesticwastewater and the reported biogas yield is 0.1–0.15 m3/kg COD removed with a methane content of 75%–80%(Khan 1995). The performance data of the plant is pre-sented in Table 5.

Subsequently, under the same project, a 14 mld unitwas designed and built in Mirzapur, Uttar Pradesh andanother 36 mld unit has been operational since March1995 in Kanpur (Tare et al. 1997). The performance ofthe plants is summarized in Table 6. A similar plant of 50mld capacity is now being built to treat the sewage inHyderabad city (Tare et al. 1997).

High rate anaerobic treatment technologies have alsobeen adopted by several Indian industries. Different

Table 5. Performance data of the 5 mld UASB demon-stration plant in Kanpur

Parameter Concentration (mg/litre)

Influent Effluent Removalefficiency (%)

COD 552 136 75.3BOD 222 44 80.2TSS 322 68 78.9

Source. Khan (1995)

reactor designs like UASB (Jalgaonkar 1995), hybridreactor (Bardiya et al. 1995) and fixed film reactor(Manihar 1995) have been employed for distillery andsugar waste treatment. Currently, there are two full-scale plants which are operational for the treatment ofpulp and paper mill effluent. A CSTR type anaerobictreatment plant has been installed in Pudumjee Pulp andPaper Mills, Pune to treat around 250 m3 effluent perday with a BOD and COD removal of approximately85% and 65% respectively (personal communication).Recently, a 3.81 m3 wastewater treatment plant basedon UASB technology was successfully commissioned atSatia Paper Mills, Punjab (Naithan, Mathur 1997). Acommercial tannery in Kanpur has installed a 10 000 li-tre capacity UASB reactor. With an HRT of 12 h, theplant was able to achieve 70% reduction in COD(Rajamani et al. 1995). The sludge produced was stable,less in volume, and had good dewatering capacity. Yetanother sector is the dairy industry which produceslarge amounts of wastewater suitable for anaerobictreatment and controlled methane production. Extensivepilot plant studies in the state of Maharashtra were car-ried out to develop an anaerobic treatment process fordairy wastewater (Tare et al. 1997). A case study in amilk processing unit in Maharashtra showed thatanaerobic treatment can achieve savings to the tune ofRs 25 million per year in Maharashtra alone (Tare et al.1997).

In addition to commercial operations, several labora-tories in India are actively involved in the R&D ofanaerobic treatment systems. A study carried out onR&D projects sponsored by the Ministry of Non-con-ventional Energy Sources (MNES) over the last 15years indicates that more than half (62%) the projectswere devoted to research while the remainder dealt withdemonstration and evaluation of the technology.

Table 6. Performance of full-scale anaerobic reactorstreating municipal wastewater

Parameters Kanpur Mirzapur(36 mld) (14 mld)

Volume (m3 ) 12 000 4800Hydraulic retention time (h) 8 8Organic loading (kg COD/m3d) 5.625 1.10Upflow velocity (m/h) 0.92 0.61COD removal (%) 24–50 49–65BOD removal (%) 25–47 58–71TSS removal (%) 29–73 50–76Effluent COD (mg/litre) 551–730 133–254Effluent BOD (mg/litre) 220–303 58–84Effluent TSS (mg/litre) 220–825 91–148

Source. Prasad (1995), Hammad (1996)

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Constraints in implementation of anaerobicdigestion technology in selected industriesThis section discusses the major barriers faced in theimplementation of anaerobic digestion in industries in-cluding distilleries, pulp and paper, and dairy.

A high strength effluent producer, the distillery sec-tor has to meet stringent pollution control regulations.This makes distilleries one of the most suitable areas forenergy generation through biomethanation. However,only 145 out of 254 distilleries in the country haveadopted anaerobic digestion for wastewater treatment(Chauhan 1998). This could partly be attributed to thefact that high rate anaerobic digestion technologies wereestablished in India during the early 1990s. Most of theplants installed prior to this period were based mainlyon the aerobic process. There is some hesitation tochange over to anaerobic technology partly due to thelack of information on installations operating success-fully, such as in the case of UASB reactors. Moreover,it is difficult to obtain reliable plant scale data becausedistilleries are unwilling to divulge the digester perfor-mance due to fear of reprisals from the pollution controlauthorities.

Although a significant potential exists for the energygeneration from anaerobic technology, most of the dairyindustries employ aerobic plants for effluent treatment.Thus, installing an anaerobic plant after demolishing theexisting aerobic unit is not acceptable due to the addi-tional cost. Moreover, being in the small-scale sectormost of them do not find it economically feasible to in-stall a treatment plant even though the high strength ef-fluent does not meet the pollution limits.

Although pulp and paper mill effluent is a prime can-didate for anaerobic treatment, instances of its use arelimited. One reason is the presence of toxic componentsin the effluent which results in non-adaptation of themicro-organisms. Apart from identifying cultureswhich can adapt to toxic compounds in the effluent, an-other solution would be to segregate the waste streamssuch that the streams containing large concentration ofchemicals are diverted away from the anaerobic diges-tion process. This could aid considerably in the effec-tive implementation of anaerobic digestion technologyin the pulp and paper sector.

Promotion of biomethanation technologyin IndiaFor over two decades, anaerobic digestion has beenused in India as a low cost method of treatment for thestabilization of sewage sludge and sewage. India is per-haps next only to China as far as anaerobic digestion ofanimal dung in small-scale plants is concerned. To meetthe growing energy needs of the country, the Govern-ment of India (GoI) has placed growing emphasis on

new and renewable sources of energy (NRSE) as is evi-dent by growing financial outlays earmarked for theSeventh (Rs 5.8 billion) and Eighth (Rs 8.51 billion)Five Year Plans (UNDP 1994). During the Eighth Planperiod, Rs 3.2 billion was allocated for promotion ofbiogas through the concerted efforts of the MNES. Sofar, 2.7 million biogas plants have been installed in In-dia, with a further potential to install 1200 millionplants (MNES 1998).

The GoI, under the chairmanship of Secretary,MNES set up the National Bioenergy Board (NBB) on 1April 1994 as the national apex agency for providingpolicy guidelines and directions for harnessingbioenergy from urban, municipal, and industrial wastes.A National Pilot Programme on energy recovery fromurban, municipal, and industrial wastes covering allstates and union territories was launched in 1995. Theprogramme aims at promotion, development, demon-stration, dissemination, and adoption of appropriateconversion technologies for both solid and liquid wastesthrough improved waste management and introductionof fiscal and financial incentives. Projects utilizingwastes from urban, municipal, and industrial sectors forenergy recovery would be set up under the NationalProgramme (MNES 1995). The overall goals and objec-tives of the programme include:• creation of conducive conditions and environment,

with fiscal and financial regime to help promote, de-velop, demonstrate, and disseminate utilization ofwaste for recovery of energy and resources,

• improvement of the waste management practicesthrough adoption of technologies for conversion ofsuch wastes into energy, and

• promoting the setting up of projects utilizing wastesfrom urban, municipal, and industrial sectors.

In addition, MNES has initiated a project partially as-sisted by UNDP–GEF for the development of high ratebiomethanation processes as a means of reducing GHGemission. This is scheduled to be completed by 1 Sep-tember 1999 and has a total outlay of Rs 400 million.The project covers up-scaling, validating, and full-scaledemonstration of mature technology. The overall objec-tives of the scheme are:• development of institutional framework at national

level to generate necessary awareness and capabili-ties to provide impetus to the Bioenergy Develop-ment Programme utilizing high rate biomethanationprocesses;

• development of requisite expertise and capabilitiesin the national and state level institutes, R&D organi-zations, and universities to assimilate and adapt tech-nologies, improve applied R&D skills in the field ofhigh rate biomethanation processes, and to provide

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technical know-how and assistance in setting upplants using the biomethanation process;

• promotion of the use of biomethanation technologyand biogas utilization as cost effective means of en-ergy generation through demonstration sub-projectsand national and local level seminars and workshops,promotional campaign, training, and demonstration;and

• development of a national master plan and a shelf ofinvestment proposals to utilize this important renew-able resource through commercialization of pro-cesses.

The scheme which originally planned to cover 16demonstration sub-projects has been expanded to covera total of 29 sub-projects in nine sectors viz., sewage(3); pulp and paper effluents (3); vegetable marketwastes (6); leather effluent/abattoir wastes (6); biogasutilization for power (4); food and fruit processing in-dustry waste (2); municipal solid wastes (2); dairywastes (1); and animal waste and agroresidues (2)(MNES 1998). Of these, four sub-projects viz., (i)biomethanation of sewage treatment, (ii) biometha-nation for treatment of slaughter house waste, (iii)biomethanation of paper mill black liquor, and (iv)evaluation of biomethanation systems have already beencompleted.

Financial incentives for promotion ofbiomethanationSome of the major incentives for the promotion ofbiomethanation technology are listed below.• Interest subsidy, i.e. 10% on the loan amount for the

entire loan repayment period, subject to maximumcapitalized amount of Rs 10 million per mega wattelectricity (MWe)

• Investment subsidy, i.e. 50% of direct equity stake inthe project cost limited to Rs 10 million/MWe

• Rs 1.5 million/MWe to municipal corporations/urbanlocal bodies, subject to their coordinated actions forfinalization of clearances/agreements for makingland available at token lease rent for minimum leaseperiod of 30 years, garbage availability free of cost atproject site, and for power purchase/ sale

• Rs 0.5 million/MWe to state nodal agencies subjectto their involvement in actions indicated above

• A sum of two per cent of the interest subsidychannelized through the lead financial institution, asservice charges, subject to a maximum of Rs 0.2 mil-lion per project on reimbursement basis

• State electricity boards are eligible for the followingincentives for the waste to energy projects:– 25% of cost of equipment for interconnection/

evacuation facilities (up to Rs 0.15 million/MWe)

– Cash incentive for power fed in to gridFirst 50 million units/year - 5 paise/unitNext 100 million units/year - 4 paise/unitNext 150 million units/year - 3 paise/unit

• Preparation of detailed project report/technical feasi-bility report etc. up to 50% of the cost, subject to amaximum of Rs 0.2 million

• Financial support of up to 50% of project cost limitedto Rs 30 million/MWe including the cost of land asper revenue records for setting up innovative demon-stration project(s) based on emerging technologies/packages

• Cost sharing of up to 50% of the incremental capitalcost of power generation system at sewage treatmentplants

Fiscal incentivesThe following tax benefits are applicable tobiomethanation projects.• Accelerated 100% depreciation in the first year• Tax holiday for five years• No excise duty on gas engines and municipal waste

conversion devices producing energy• Concessional custom duty of 10% for all goods, im-

ported by a manufacturer / supplier for the manufac-ture and supply of machinery and equipment to apower generating plant (other than captive powergenerating plant)

• Concessional customs duty (20% custom duty +13% countervailing duties) on project import

ConclusionsThough anaerobic digestion systems have been opera-tional in certain industries like distilleries for sometime, there is still some apprehension regarding adopt-ing this technology in other sectors. This stems fromvarious factors like limited availability of experiencedconsultants to implement the technology, little full-scaleexperience, lack of operator training within the indus-tries for process maintenance, and restricted interactionbetween research organizations and commercial devel-opers/vendors. Since a large number of Indian indus-tries are yet to establish adequate wastewater treatmentfacilities, the GoI is actively promoting anaerobic diges-tion technology. Apart from funding pilot studies, fi-nancial and fiscal incentives are also provided forestablishing full-scale plants. Also, under the UNDP–GEF assistance programme, MNES is encouraging bothnational and international entrepreneurs to demonstrateproven anaerobic technologies in various industrial anddomestic sectors. In addition, there is an urgent need formore intensive interaction between research organiza-tions and suppliers of anaerobic systems. This is sup-ported by the fact that over the last 15 years, even

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though MNES has sponsored more than 90 researchoriented projects on biogas production, there is still lackof sufficient design information. Out of the nearly 60demonstration projects, only one has been scaled up forcommercial operation. This indicates a wide gap be-tween R&D efforts and technology implementationpointing to the need for more effort towards technologyadoption aspects.

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