Waste to Energy Technologies and Pathways

Every year tons and tons of waste are generated world over. Despite our best efforts to reduce, reuse and recycle, waste keeps arising. Globally the estimated quantity of just the solid wastes generation alone was 12 billion tons in the year 2002 and about 19 billion tons of solid wastes are expected to be generated annually by 2025. In India alone, 1700 million tons of waste is generated from various sources. The waste management market valued at $ 227 million in 2008 is expected to reach $ 600 million in 2013.

Solid waste generation in India (2010) (in MT/ yr)

Organic solid waste such as cattle waste, poultry waste etc…	985
Agro waste/ gardening waste including coffee/sugar/natural rubber/pulp, farm waste, used flowers, vegetable waste etc…	660
Sewage sludge, human manure etc.	72
Other wastes (office waste (including shredded paper), slaughterhouse waste, Dairy & food processing plant effluent.	300

In a broad sense wastes can be classified into solid wastes, liquid wastes and special wastes. Categorization of waste with an almost exhaustive list of examples has been summarized in the below figure

A number of solid, liquid and gaseous fuels can be generated from these wastes through diverse technologies. They can be used for various applications in power, transport and heating.

Solid fuel refers to various types of solid material that are used as fuel to produce energy usually by the process of combustion or gasification. Solid fuels include briquettes, charcoal, pellets and solid recovered fuel (SRF). The most important liquid fuels include ethanol, biodiesel, bio oil, synfuels and other hydrocarbon biofuels. Gaseous fuel apart from being used for power is also increasingly being used for transport and heating. Some of the gaseous fuels include biogas/methane, syngas/producer gas etc.

In the following sections, we analyze the technology options for reusing waste for energy recovery and also find out the business opportunities that lie along the value chain.

There are a number of new and emerging technologies for producing energy from waste without direct combustion. While it is tough to summarize all the technologies in a single flow diagram, we have attempted to compile the main categories and processes for waste-to-energy generation.

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