Waste Biomass to Energy

Published on 17/05/2011

First Update 14/03/2017

Biomass wastes are generated in large quantities in developing countries especially in the Asia Pacific region. Agricultural Farms/ Fields in urban areas, agro processing industries, urban vegetable market places, road sweepings and road side plantations are some areas which generate significant biomass waste. The management of these areas is generally in the hands of poor farmers and the unorganized sector, rural households and the low income tiny agro based industry sector. Almost 200 million tones of household and agro processing wastes are generated annually in India and disposed in a dispersed manner .Since they are associated with little or no production costs they are either unused or utilized  inefficiently. Large amounts of leafy wastes are burnt resulting in air pollution. Effluents and other wastes create problems of Water and soil pollution. Dumping has serious consequences. During the process of organic decomposition of these wastes on land, organic matter percolates into the ground water or runs off to surface waters causing pollution which leads to health hazards and fish mortality.

These wastes have a renewable energy potential and a   potential of reutilization in an Environment friendly way. Some estimates are as follows:
Distillery-350 MW
Sugar-285MW
Paper and Pulp-58MW
Dairy-58MW
Poultry-44MW
Starch-40MW
Slaughter Houses-100MW

To utilize these wastes gainfully, farmers, rural cottage agro industries and their associations, local governments and Municipal organizations, NGO’s and self help groups  can be mobilized . This would give a decentralized energy generation source, improve the working and living conditions and gives a cleaner local and global environment.

Many Industries in India have started using Biomethanation Technologies. The gas produced serves as a useful source of energy while the slurry has a good fertilizer potential. The savings in fossil fuel has resulted in reducing costs and thereby increasing profits.

At a biomethanation plant installed in Sakthi Sugars, Maharashtra the Internal Rate of Return has been reported as high as 32% and the Biogas substituted for almost 87% of the consumption of Furnace oil. A biogas based power plant of 1 MW capacity was installed at the K.M.Sugar mills in Uttar Pradesh with financial assistance from the Ministry of Non Conventional Energy Sources, Govt. of India. It utilizes 12000 cubic meters of biogas produced from 400 KL of spent wash per day. Kanoria Chemicals Ankleshwar has installed a 2 MW power plant based on biogas.

Many Sugar mills have also started using press mud, earlier considered as waste, for the production of biogas. Press mud has 75% organic matter and 29% total solid content out of which 65% is volatile. Four biogas plants each having a capacity of 85 cubic meters were set up at the Pravarnagar, Sugar Factory at Maharashtra with financial assistance from the MNES, Govt. of India .A biogas yield of 165 liters of Biogas per Kg. press mud (having 60% methane) with a processing time of 35 days was observed during monitoring of the stabilized biogas plant. The biogas from the plant was piped to 196 households within factory premises for 4 hours daily to meet cooking needs.

The Pradeshik Investment Corporation of U.P. (PICUP) had estimated that a 60000 TPA biofertiliser unit based on spent wash and press mud would require an investment of Rs. 209 lakhs( Land,116;Building,6.00;Plant machinery59.90 plus others). PICUP envisages a debt equity ratio of 1.49:1. Manpower required is 10 and the total power requirement is 400KVA.The cost of production works to Rs. 400 per ton, the selling price Rs. 1000 per ton and a repayment of 5 to 6 years.

Cane leaves left in the fields after harvesting of sugarcane form a thick mat on the fields and are generally burnt in the open fields without extracting any form of energy causing widespread pollution. An NGO called the Appropriate Technology Institute (ARTI) has developed an oven and retort kiln technology to char leafy waste. The plant can be operated by three persons and generate 100Kg. per day of char which can be turned into briquettes by using an extruder. In a period of 25 weeks during the sugarcane harvesting period, a family can generate about 15 tonnes of Briquettes which would earn an income of Rs. 75000. Under the Ashden Award a project using this technology aims to manage 4.5 million tones of sugar cane wastes generated in Maharashtra. Ten Sugarcane demonstration plants will be set up in Maharashtra. These briquettes are being used as a source of fuel and in innovative applications like keeping food warm in Tiffin boxes for long periods.

Leafy wastes can be a rich source of biogas. The biogas potential of leafy wastes is almost twice that of cow dung. The total annual production of leafy biomass in India is of the order of 1130 million tones. Even if 10% of this be mobilized for biogas production about 2/3rd of the rural families estimated at 100million rural households could be provided with biogas for cooking. ASTRA, IISc., has successfully developed and demonstrated several “plug flow” biogas plants in the field using leafy biomass as feed material in the southern states of Kerala.

Paper production is energy intensive. Energy costs account for more than 30% of the cost of paper production. Chemical recovery in agro based paper mills is a major constraint with most of the industries discharging untreated or partially treated black liquor which accounts for more than 80% pollution from such mills. Biomethanation plants for pulp and paper mill effluents have been installed at a few places in India and the gas is being flared to the boiler and cofired with rice husk.

Slaughter houses generate considerable solid and liquid wastes Al Kabeer Exports Pvt. Ltd, Medak, Andhra Pradesh has installed an indigenously developed two stage digestion process which handles 60MT of slaughter house wastes per day. The second stage uses modified UASB Technology. The 3000-4000 cubic meters of gas produced per day reduced the furnace oil consumption by over Rs. 40 lakhs per annum. The dried sludge almost 20 TPD is used  as  manure.

Poultry wastes can also be used to produce energy. Western Hatcheries Has installed a demonstration biogas  plant based on UASB technology to treat about 600 Kg. of poultry waste. The biogas produced is collected in gas balloons, pressurized and piped for use in canteen Kitchens. The sludge is used as a fertilizer. The plant is producing 60 cubic meter of gas per day which is equivalent to 24 Kg. of LPG. A 1.2 MW power project for 200 TPD of poultry waste has been set up at Namakhal. The total cost of the project was 14 crores with a capital subsidy of Rs. 3.5 crores.

Pine needles are a difficult forest waste. They cannot serve as fodder. They do not decay as other biomass and piled up pine needles are a major source of forest fires. They are however a good source of biomass fuel. Briquettes made up of charred pine needles are being used in the hill regions of Kumaon and Garhwal. Cities like Gurgaon are using briquettes from local biomass like bagasse and vegetable market wastes.

The organic fractions of municipal wastes can be gainfully utilized to produce biogas. The Technology Informatics Design endeavor (TIDE) in collaboration with the Centre for Sustainable Technologies, IISc., has implemented a project for the conversion of the organic fraction of Municipal wastes into energy and resources in Singupa town, Bellary District. A plug flow biogas reactor has been designed. Data collected shows that 1 Kg. waste gives between 50 to 60 liters of biogas. The C/N ratio of compost was found to be 11.4. Segregation and transportation are limitations that need redressal.

Coffee pulping wastes are a rich source of biogas too. The Indo Norwegian Environment project and the Coffee Board in the Ministry of Commerce have supported a project for biogas generation from coffee pulping wastes. High B.O.D. effluents can be treated in bioreactors to give biogas. The B.O.D. of the treated effluents has been reported to be below the standards prescribed. About 80 cubic meters of biogas is produced for every ton of coffee parchment. 1 cubic meter gas substitutes 0.5 Kg. LPG in cooking operations and 0.25 liters of diesel in dual fuel mode of operation in the generation of 1KWH of power. The technology has been demonstrated in 13 locations and is working satisfactorily. In the off season the bioreactor may be fed with other waste biomass like coffee husk, leaves, grass etc. to produce gas.

A bioreactor for canteen wastes has been installed at the Transport House, KSRTC,Bangalore. This reactor is an immobilized cell bioreactor- a high rate biomethanation plant  using spent biomass as support for the methanogenic bacteria. The biomass would range from rice straw, bagasse, paper shreds, garden cuttings, lawn mowing, vegetable peels, uneaten rice, plate and dish washings, fruit and vegetable rejects etc. On the basis of raw material fed to the reactor every Kg. of feed produces 50 to 80 liters of Biogas. The KSRTC plant can handle 25 Kg. of canteen rejects per day along with the leaf litter. About 1.5 cubic meter of gas is produced every day. At present the gas is being used to keep the food warm.

TERI initiated a project in 1996 for the development of a high rate reactor for biomethanation of fibrous and semisolid organic wastes. Consequently the TERI enhanced acidification and methanation process was developed and patents applied. A 50 Kg. per day green leafy vegetable waste treatment plant is operational at TERI’s Gurgaon campus at Gual Pahari. This has now been converted into a canteen waste treatment plant. Good quality biogas and manure is being generated. The TEAM (TERI Enhanced Acidification and Methanation) is a two stage process. The first phase consists of extracting a high concentration leachate (C.O.D. 15000-20000 Mg. / liter) from the solid waste in the acidification reactor. In the second phase the leachate is treated in the UASB reactor with retention of 16 hours to give methane and more than 60% C.O.D. is discharged. The acidification process residue is good quality manure after drying. The biogas consists of 70 to 75% methane, Carbon dioxide, traces of Hydrogen Sulphide and moisture. The biogas production rate is 0.45 cubic meter per Kg. of C.O.D. removed. The TERI process shows a useful way to turn wastes from food and fruit processing industries, hotels, pilgrim houses, hostels, housing colonies, community kitchens, vegetable markets etc. into wealth. Vegetable markets can produce 20 cubic meters biogas / ton of waste, fruit and vegetable processing 20 cubic meter /ton, press mud 9 cubic meter/ton, food wastes 54 cubic meter/ ton and coffee pulp 10 cubic meter/ton. The manure is richer in N.P.K. than any other natural manure.

The Ministry of Non conventional Energy Sources, India is publishing a news letter named Bioenergy News.

References
www.iges.or.jp/APEIS/RISPO/SPO/Pdf
www.picupindia.com
www.wmc.nic.in/case-studies.asp
www.teriin.org
www.tide-india.org
www.ficci.com
www.mnes.nic.in
www.cgpl.iisc.ernet.in