Technological Options for Energy Recovery fromWaste2.1 Basic Techniques of Energy Recovery from WasteEnergy can be recovered from the organic fraction of waste (biodegradable as well asnon-biodegradable) through thermal, thermo-chemical and biochemical methods. (Eaiwaste to Energy treatment process, 2011)A brief description of the commonly applied technologies for energy generation fromwaste is as follows2.

1.1 Anaerobic Digestion/Biomethanation (commonly called as gobar gas)This techologies has been used in India since ages for treatment of waste and it is Indigeneous technologies yet this technology faces lack of fund and research due to which wewaste the huge potential it can provide. In this process, the organic fraction of the waste(Fruit and vegetable remains, Cattle dung and human excreata) is segregated and fed intoa closed container (biogas digester). In the digester, the segregated waste undergoesbiodegradation in presence of methanogenic (methane producing) bacteria and underanaerobic(without air/oxygen) conditions, producing methane-rich biogas and effluent.The biogas mostly methaneCH4 can be used either for cooking/heating applications,or for generating motive power or electricity through gas engines, low-pressure gas turbines, or steam turbines like we use in thermal power plants.

The sludge from anaerobicdigestion, after stabilization, can be used as a soil conditioner (bio-Manure) which isbetter alternative than fertilizer in terms of soil quality and environmental protection.4It can even be sold depending upon its composition, which is determined mainly by thecomposition of the waste input.2.1.2 Combustion/IncinerationA rather easy way to deal with waste but environmentally polluting one, with low credibility to give positive economic potential.

In this process, wastes are directly burned inpresence of excess air (oxygen) at high temperatures (about 800oC), which liberats heatenergy, inert gases, and ash (many of which is harmful). Combustion results in transferof 65% {80% of heat content of the organic matter to hot air, steam, and hot water. Thesteam generated, in turn, can be used in steam turbines to generate power.2.1.3 Pyrolysis/ GasificationA rather new technique which is still being tested in many countries like sweden and chinahas the potential to be the main technologies o be used in future.Pyrolysis is a processof chemical decomposition of organic matter brought about by heat.

In this process, theorganic material is heated in absence of air until the molecules thermally break down largemolecules to gas comprising smaller molecules (known collectively as syngas(mixtureCOand H2)) has large use in chemical production.Gasification can also take place as a result of partial combustion of organic matter inlimited supply of oxygen or air. The gas so produced is known as producer gas(MixtureofCO and N2). The gases produced by pyrolysis mainly comprise carbon monoxide(25%), hydrogen and hydrocarbons (15%), and carbon dioxide and nitrogen (60%). Aftercleaning the syngas or producer gas the gas is burned in internal combustion (IC) enginegenerator sets or turbines to generate electricity.2.

1.4 Landfill Gas recoveryA suitable technology for present Scenario, acheap and minimal infrasture is required toproduce electricity. The waste dumped in a landfill becomes enclosed, over a period oftime, to anaerobic digestion. As a result, its organic fraction volatilizes and decomposes,leading to production of ‘landfill gas'(again methane), which contains a high percentageof methane (about 50%).Methane if we let it go to atmosphere is in itself has 30 times more green housepotential than carbon dioxide while it can be utilized to form energy and will convert toless green house potentialCO2. Methane burn with non-sooty flame and leave no ashafter burning and thus a cleaner fuel.

3 Indian Government Support for Waste to EnergyProjectsMNRE has promoted the national programme for the recovery of energy from industrialand urban wastes. Various financial incentives and other eligibility criteria have beenproposed by MNRE to encourage the participation in waste-to-energy projects. Theseare listed below:• Financial assistance will be provided by way of interest subsidy for commercialprojects