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In a previous article I have discussed why we as humans would process waste (mainly solid) as a source of energy. There is plenty of waste to collect and dispose so why not use some of them to obtain some energy?
On the other hand, waste is a problem for our society because waste is a source of environmental and public health concerns. Both problems (increased amounts of solid and liquid waste being generated and tapping new sources of energy) can be solved by looking at waste as an alternative source of energy. Technology is available to efficiently convert waste to energy.
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Waste to Energy plants: How do they work?
Basically, a waste to energy plant work very much like a coal (or petroleum) plant. But instead of burning coal (or oil), a waste to energy plant uses garbage as fuel. In very simple terms a waste to energy plants follows four basic processes:
1. The waste (plant fuel) is burned. Heat is released.
2. The heat is used in a boiler to convert water into steam.
3. The steam is used to move the blades of a turbine to generate electricity.
4. The generated electricity is sent, along power lines, to the final users (homes, schools, businesses).
Experts have calculated the amount of energy that can be “extracted" from solid waste. A typical mix of urban solid waste (that includes paper, plastic, some organics) can produce more than 500 kilowatt-hours (kWh) of electricity per 1000 Kilograms. Thins electricity is said to be enough to be used by an office in a building for an entire day.
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Waste to Energy Plants help to Reduce the Amount of Waste to Dispose
In addition to generating energy from solid waste, a waste to energy plant helps decrease the amount (tonnage) of waste needed for final disposition in landfills, reducing, thus, the environmental and public health concerns. Burning waste leaves a small fraction of solid waste called ash. The percentage of ash left, after using waste to generate electricity, is variable and depends on the waste being used but it can range from 15 to 20%. So, 100 Tons of solid waste can be reduced to 15-20 tons of ashes to finally dispose in a landfill.
There are many places in the world (and in the US) where waste is used to generate electricity. Waste to energy plants are seen as a way to solve two of today’s most pressing issues: energy scarcity and reduction in waste to be disposed.
Turner and Heffington. 2004. Energy Management Handbook: CRC Press