If you've had a chance to see Slumdog Millionaire, then you would have seen the visually striking chase of the young kids by a policeman through the Mumbai slums. Remember the shots of colorful garbage stewn throughout the slum? I wish I could say it was a fake scene, but its not. Within minutes of landing in India, you would realize what a nightmare garbage in India is. The stench, the ugly sight of garbage on roads and over flowing from drains is disgusting until you become conditioned and then blind to it.

Indian cities are under a serious threat of being overwhelmed by the garbage generated everyday by their citizens. Landfill is the only way of waste disposal by Indian municipalities. And all the waste is dumped on abandoned land without any treatment or planning. So if cities exhaust a land, they just find another one to dump garbage on. The Energy Research Institute estimates that 1400 sq. km. of land would be required by 2047 for municipal waste! The cities which had the luxury of a river flowing through them, strangled them by dumping their wastes into them. Yamuna, flowing through Delhi, has practically no living creatures in it.

The World Bank estimates that India's per capita waste generated in urban areas will grow from 0.2- 0.6 kg to 1 kg per head per day by 2030, when the population would be 600 million. Limited by a small budget marked for waste disposal, make city’s Urban Local Bodies (ULBs) ill-equipped to operate an efficient waste collection, storage, treatment and disposal system. So currently 90% of urban waste generated is dumped on low lying land in environmentally unsound methods. With land being a scarce commodity this practice is clearly unsustainable and unsafe for human health and environment. The local municipal bodies need to strategize for managing the rapidly growing amount of waste generated daily. Today they manage to collect only about 50% of the waste, while the rest continues to collect in urban areas.

One method to dispose waste that is being considered, but not seriously enough are waste-to-energy plants. These plants will reduce the physical size of waste to be disposed and also generate electricty to supply to the grid. According to the 10^th National Plan from 2002-03 to 2005-06, estimated capacity for WtE projects in 2100 MW, but currently 34.5 MW of grid connected WtE projects exist.

The amount and characteristics of non-recyclables in Municipal Solid Waste (MSW) dictate the technology for WtE. Indian MSW composition contains higher biodegradables than in the developed nations, and also a lower calorific value due to higher moisture content. Composting had been proposed as a viable solution, but poor yields coupled with requirements for large land to dispose the rejects, resulted in many failed projects. WtE seems to be most qualified solution to waste treatment because it reduces volume of waste in landfill to 60%-90% and also decreases the amount of greenhouse gas emissions from landfills.

I've described some appropriate technologies for India:

All definitions have been taken from Wikipedia, while the notes are Indian contextual additions.

1. Incineration: Incineration, the combustion of organic material such as waste, with energy recovery is the most common WtE implementation. Modern incinerators reduce the volume of the original waste by 95-96 %, depending upon composition and degree of recovery of materials such as metals from the ash for recycling. Incineration without energy and materials recovery is being increasingly banned in OECD countries.

Note: Almost all the operating incineration plants take a feedstock of industrial or agricultural wastes. Incineration of urban wastes in India have been largely unsuccessful because of the nature of the wastes and highly polluting because of the lack of regulation in attaining emission standards in air control(which add to nearly 35% of capital costs abroad). (wiki)

2. Co-firing: Co-firing burns the feedstock (refuse derived fuel) in combination with a fossil fuel, most often coal. This process can reduce overall air pollution emissions, notably sulfur. Nevertheless, co-firing processes do produce some air pollution emissions, and the main concern with these is the release of unburned particles that eventually cause human health issues. Refuse derived fuel (RDF) is a fuel produced by shredding and dehydrating municipal solid waste (MSW) in a converter or steam pressure treating in an autoclave. RDF consists largely of organic components of municipal waste such as plastics and biodegradable waste. 

Note: One of the advantages of co-firing is that an existing plant can be used to burn a new fuel, which may be cheaper or more environmentally friendly. Also it can be used to improve combustion of materials with low energy content, which allows for better equipment performance and decrease in pollutants. (wiki)

3. Gasification: Gasification is a process that converts carbonaceous materials, such as coal, petroleum, biofuel, or biomass, into carbon monoxide and hydrogen by reacting the raw material, such as house waste, or compost at high temperatures with a controlled amount of oxygen and/or steam. The resulting gas mixture is called synthesis gas(syngas) and is itself a fuel. Gasification is a method for extracting energy from many different types of organic materials. The using the syngas is potentially more efficient than direct combustion of the original fuel because it can be combusted at higher temperatures or even in fuel cells. Gasification occurs at greater than 700°C which differentiates it from anaerobic digestion. Note: Almost any organic material even plastic can be used as feedstock, which decreases the need for segregating waste. It has tremendous potential to be used as a way to utilize urban waste. But previous installations have not resulted in positive net energy production. (wiki)

4. Anaerobic digestion: Anaerobic digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen. It is most widely used to treat waste water sludges and organic waste and It produces three principal products: biogas, water and digestate. The biogas is about 50-75% methane and rest is majorly CO2. The released CO2 is not considered to increase atmospheric CO2 concentrations because it comes from an organic source with a short carbon cycle. The water needs further treatment before usage. The digestate can be used as a soil fertilizer with high organic content.

Note: Establishing a plant requires low investment and such plants have been promoted by the Indian government as one of the most useful methods decentralized cheap electricity generation. There’s also potential for gaining additional financial support through the CDM. (wiki)

5. Landfill gas power: Large municipal or industrial landfills produce gas that can be tapped to generate electricity. Microorganisms that live in organic materials such as food wastes or paper cause these materials to decompose. This produces landfill gas, typically comprised of roughly 60 percent methane and 40 percent carbon dioxide (or "CO2"). Landfill gas is collected from landfills by drilling "wells" into the landfills, and collecting the gases through pipes. Once the landfill gas is processed, it can be combined with natural gas to fuel conventional combustion turbines or used to fuel small combustion or combined cycle turbines. Landfill gas may also be used in fuel cell technologies, which use chemical reactions to create electricity, and are much more efficient than combustion turbines. Landfill gas if not used will emerge as methane and CO2 into the atmosphere. 

Note: Specially designed landfill sites are needed to tap the gas. Currently none exist, but construction is not very high capital intensive. Existing landfill sites in developed world show that profitability is low, but nevertheless this is a possible source of decreasing carbon emissions and producing electricity. (wiki)

Past experiences with WtE:

Several small decentralized projects utilizing industrial waste have been successful in generating energy for local captive usage. But experience with generating energy from MSW has been unsatisfactory so far.

MSW based private WtE projects had contractual agreements with a ULB for delivery of waste. International ULBs typically pay a tipping fee to the WtE operator for accepting the waste. But in India contrary to payment of tipping fee, ULBs expected royalty from the profits generated through waste treatment. The energy generated was generally fed to the local grid under a Power PurchaseAgreement (PPA).

Projects setup in Timarpur (Delhi) and Lucknow shut down due to mismatch of wastes received and plant design. Also lack of accountability on part of the ULB in waste segregation and regularity aggravated the problems.

The Refuse Derived Fuel (RDF) plants set up in Hyderabad and Vijayawada still operate, but at a fraction of their installed capacities of 6 MW each. To overcome the low calorific values of MSW received they supplement the feedstock with agricultural waste. But these plants remain underutilized due to desired amount of MSW not being received.

Other projects make it clear that major issues have been quality and amount of MSW received due to lack of a strategy in waste disposal and poor administration of ULBs. Additionally technology development and adaption to Indian scenario has also been an issue. Project viability was further hindered by disputes and litigations over payment of compensation by ULBs for non-delivery of agreed feedstock in return for a royalty on profits generated.

Due to lack of awareness among the public and ULBs there has also been some resistance to these facilities owing to increased levels of local pollution and health hazards from these setups. This resistance resulted in slower land acquisition as well.

Soon afterward the government of India (GOI) was slapped with several litigations against providing subsidies without any analysis of the WtE projects. But in the past couple of years there has been increasing initiative by the government of India to restart the WtE market.

Renewed support:

In 2007 the Supreme Court allowed the GOI to subsidize five commercially run WtE plants on a pilot basis and take a decision on future of WtE on the basis of these pilot operations. In 2008 three MSW processing plants with power plants were awarded to private players. Two of the projects are MSW with attached power plants while one is an integrated MSW Management plant. These projects were developed on the basis of the recommendations of the SC Expert Committee on Solid Waste Management through special purpose vehicles (SPVs) which undertook waste characterization, plant design, technology selection, engineering and finalizing all contracts. These SPVs were transferred to successful bidders following a tariff based competitive bidding system.

The Twelfth Finance Commission has recommended states to provide grants to support collection, segregation and transportation of MSW under the Jawaharlal Nehru National Urban Renewal Mission to boost waste management in 63 big cities of the country. The GOI has also promised a subsidy of USD 30m (INR 150 crore) for MSW projects according to project type and scope.

So there is some momentum at the center to find solutions to the growing problem of disposing waste, but the local bodies are not adequately equipped to locally solve the issues. Additionally project developers need to understand local wastes carefully before introducing a technology that was previously successful in a different country.