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16.10.2015, 23:03 | |
BIOFUEL Biofuels are produced from living organisms or from metabolic
by-products (organic or food waste products). In order to be considered a
biofuel the fuel must contain over 80 per cent renewable
materials. It is originally derived from the photosynthesis process and can
therefore often be referred to as a solar energy source. There are many pros
and cons to using biofuels as an energy source. Unlike other
renewable energy sources, biomass can be converted directly into liquid fuels -
biofuels - for our transportation needs (cars, trucks, buses, airplanes, and
trains). The two most common types of biofuels are ethanol and biodiesel. Ethanol is an alcohol, the same found in beer and
wine. It is made by fermentation of any biomass high in carbohydrates
(starches, sugars, or celluloses) through a process similar to brewing beer.
Ethanol is mostly used as a fuel additive to cut down a vehicle's carbon
monoxide and other smog-causing emissions. But flexible-fuel vehicles, which
run on mixtures of gasoline and up to 85% ethanol, are now available. Biodiesel is made by combining alcohol (usually
methanol) with vegetable oil, animal fat, or recycled cooking greases. It can
be used as an additive to reduce vehicle emissions (typically 20%) or in its
pure form as a renewable alternative fuel for diesel engines. Other biofuels
include methanol and reformulated gasoline components. Methanol, commonly
called wood alcohol, is currently produced from natural gas, but could also be
produced from biomass. There
are a number of ways to convert biomass to methanol, but the most likely
approach is gasification. Gasification involves vaporizing the biomass at high
temperatures, then removing impurities from the hot gas and passing it through
a catalyst, which converts it into methanol. Most reformulated
gasoline components produced from biomass are pollution-reducing fuel
additives, such as methyl tertiary butyl ether (MTBE) and ethyl tertiary butyl
ether (ETBE).
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