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 Trash collection has reached a saturation
point in Mumbai. BMC is already looking into the means
of using the waste to create energy. But with high costs
to create such a plant they are ready to pay over Rs 300
crore to create another garbage dump.
The Americas, European countries are already trying to
create energy from waste through different methods.
Garbage contains valuable raw materials and also energy,
which can be reclaimed in a number of ways. The oldest
process is capturing the methane gas given off by
rotting organic materials. Small-scale production is
simple, but it needs considerable amounts of manure or
other organic materials. These facilities produce clean,
renewable energy through the combustion of solid waste
in specially designed plants equipped with modern
pollution control equipment to clean the emissions.
For example in America the trash volume is reduced by
90% and the remaining residue is regularly tested and
consistently meets strict EPA standards allowing reuse
or disposal in landfills. There are 89 such plants
operating in 27 states managing about 13 percent of
America’s trash, or about 95,000 tons each day.
Waste-to-energy generates about 2,500 megawatts of
electricity to meet the power needs of two million
homes, and disposes trash of over 36 million people.
This $10 billion industry employs more than 6,000
American workers with annual wages in excess of $400
million.
EPA data shows that the dioxin emissions have decreased
by 99% in the past ten years, and have less than
one-half of one percent of the national dioxin. Mercury
emissions have gone down by more than 95% and now
represent two percent of man-made mercury emissions.
This helps avoid 33 million metric tons of carbon
dioxide that would otherwise be released into the
atmosphere.
They recycle more than 700,000 tons of ferrous metals
and more than 3 million tons of glass, metal, plastics,
batteries, ash and yard waste. This method helps promote
energy diversity by helping cities meet the challenge of
trash disposal. These plants generally operate in or
near an urban area, easing transmission to the customer
with the power being sold as “base load” electricity.
At the incinerator there exists a “bag house” that works
like a giant vacuum cleaner with hundreds of fabric
filter bags that clean the air of soot, smoke and
metals.
· A “scrubber” sprays slurry of lime into the hot
exhaust. This neutralizes acid gases, just as a gardener
uses lime to neutralize acidic soil. Scrubbing also can
improve the capture of mercury in the exhaust.
· “Selective Non-Catalytic Reduction” or “SNCR” converts
nitrogen oxides – a cause of urban smog – to harmless
nitrogen by spraying ammonia or urea into the hot
furnace.
· “Carbon Injection” systems blow charcoal into the
exhaust gas to absorb mercury. Carbon injection also
controls organic emissions such as dioxins
residue from waste-to-energy facilities represents about
10% by volume of the original trash. Ash makes good
cover in landfills because it exhibits concrete-like
properties causing it to harden once it is placed and
compacted in a landfill, reducing the potential for
rainwater to leach contaminants from trash landfills
into the ground. Nearly 3 million tons of
waste-to-energy ash is beneficially reused as landfill
cover, roadbed or building material.
Source: - www.wte.com
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