Re: How does trash become electricity?
Date: Sun Jun 28 00:28:09 1998
Posted By: Madhu Siddalingaiah, Physicist, author, consultant
Area of science: Earth Sciences
Some types of trash is disposed by burning in large incinerators. The heat
from the fires can be used to generate electricity in the same way is coal
fired power plants. The heat is used to boil water and produce high
pressure steam. The steam is allowed to expand and cool inside turbines.
The turbines turn electric generators which produce electricity.
Recycling aluminum doesn't directly produce electricity but it helps to
reduce the demand for electricity. Extracting pure aluminum from the ore
consumes a large amount of electricity. The ore is called Bauxite, named
after a city in France where it was first found. Recovering pure aluminum
through recycling takes much less electricity, so we save energy and money.
Bob Peeples adds:
Because of big changes in the public utility regulations, this has beco
one of the fastest growing industries in the United States. I spoke wit
Ms. Ann Murphy, Recycling Edu
Specialist for the Spokane, Washington Regional Solid Waste System.
There are two common ways to recover energy from refuse:
The Spokane Regional Solid Waste System also prints a really nice
newsletter called Recycling RAP. I got some of the information a
from their February, 1998 issue. I'll bet that Ms. Murphy would send yo
one if you e-mailed her with your Postal address!
- If the waste material has already been sent to a landfill, it will
decomposing and will be producing methane gas. This is a "greenhouse ga
and is normally burned up in a flare so that it is not released to the
environment. The methane gas can be used to power large engines that dr
electric generators. The City of Spokane has two G398 Caterpillar engin
that convert methane to 900,000 watts (enough energy to run 15,000 60W
light bulbs, 24 hours a day). Spokane started producing commercial powe
with these new engines about two weeks ago.
- Waste can also be delivered directly to a steam turbine electric po
plant. The City of Spokane also has one of these. The picture above is
schematic diagram of the Spokane waste to energy plant, and is linked t
their web site if you would like more detailed information. They have u
this plant to produce electric power since 1991, and have processed abo
million tons of solid waste into electric power since it opened. They f
the trash into a burner that operates at about 2000°F to heat a
boiler. The boiler produces steam to drive a turbine generator. Twenty
truckloads of waste is reduced to one or two truckloads of ash in the
process, so the landfill will last much longer. Special filters and gas
"scrubbers" clean the exhaust for release into the air.
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