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Freshwater Management
Series No. 7
Phytotechnologies
A Technical
Approach in Environmental Management
III. Examples
of Environmental Applications of Phytotechnology >
J. Bio-Energy
Biofuels, such as ethanol and methane are commonly produced from plants grown
and harvested for this purpose and from waste plant biomass, including wood
or agricultural residues. These sources of energy are renewable and relatively
clean, and can be produced in most regions where pla nts can be grown.
Brazil, for example has produced fuel alcohol for years from fermented sugar
cane. Fuel-making factories are built in areas where the cane is grown, minimizing
the need for transport. Cane debris left behind after the fermentable juice
is squeezed out is used as boiler fuel, supplying steam for stills, sterilization
of equipment, and local electrical production. Since no other fuel is required
for these operations, the fuel alcohol produced is a net gain.
The biggest part of the carbohydrate content in plants is not in the form
of either starch or sugars but in cellulose – the material making up
the structural cell walls of stems, leaves, hills, husks, cobs, etc. Lignocellulose
(a mixture of cellulose, hemicellulose, and lignin) in wood and paper wastes
makes a vast, cheap, widespread and largely untapped renewable source of biomass
that can be converted to fuel. However, lignocellulose is very difficult to
break down and convert into sugars and alcohol. The breakdown of cellulose
alone re leases a mixture of sugars, including glucose, xylose, mannose, galactose
and arabinose. Work is now being done to determine the best enzymes for rapidly
and efficiently metabolize all of these sugars into ethanol With the right
microbes feeding on the sugar residues found in waste paper and other biomass,
significant quantities of ethanol could be produced each year.
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