Page 15 - Energy from Toxic Organic Waste for Heat and Power Generation

4 Energy from Toxic Organic Waste for Heat and Power Generation

become a subject of concern globally and nationally. The more advanced
the human settlements, the more complex the waste management. There is
a continuous search for wide-ranging solutions for this problem, but it is
increasingly realized that solutions based on technological advances with-
out human intervention cannot sustain for long and this, in turn, results in
complicating the matters further. Management of waste which generally
involves proper segregation and scientific recycling of all the components
is in fact the ideal way of dealing with toxic waste. Waste management is a
commonly used name and defined as the application of techniques to en-
sure an orderly execution of the various functions of collection, transport,
processing, treatment, and disposal of waste. It has developed from its early
beginnings of mere dumping to a sophisticated range of options including
reuse, recycle, incineration with energy recovery, advanced landfill design
and engineering, and a range of alternative technologies. It aims at an over-
all waste management system which would be the best environmentally and
economically sustainable for a socially acceptable method. This not only
would avoid the above referred consequences, but give economic or mon-
etary returns in some or the other forms.
Nonetheless, land filling is still the dominant waste management option
for the United States as well as many other countries around the world.
Landfill releases biogas by the decomposition of garbage. Biogas is com-
posed of methane and carbon dioxide. Methane is a by-product of the an-
aerobic digestion of waste by the bacterial community, and these bacteria
thrive in landfills with high amounts of moisture. Methane concentrations
can reach up to 50% of the composition of landfill gas at maximum anaer-
obic decomposition. In developing countries, few landfills have the facility
for methane recovery as the required capital for methane recovery instal-
lations is lacking. The methane gas seeps into porous soil surrounding the
waste and eventually migrates into basements, posing an explosion risk.
Carbon dioxide buildup may cause asphyxiation. Carbon dioxide is readily
absorbed for use in photosynthesis, but methane is less easily broken down
and is considered 20 times more potent as a greenhouse gas. For every
metric ton of unsorted waste (containing 0.3 Mt. carbon), 0.2 Mt. are con-
verted to landfill gasses. Of this gas, carbon dioxide and methane each com-
prises 0.09 Mt. It is believed that landfill gasses supply 50% of human-caused
methane emissions and 2%–4% of all worldwide greenhouse gasses; this is
clearly an area of concern in global environmental issues. The capture of
methane from landfill gas (biogas) and its filtration by adopting either cryo-
genic separation, membrane separation, or chemical separation may lead to