Environmental Engineering Reference
In-Depth Information
gasoline mix. The production of this ethanol requires about 1% of Brazil's
total farmable land. Sugar cane can be grown nearly year-round in Brazil
but the program has required government assistance. These subsidies for
the production of ethanol from sugar cane have totaled several billion dol-
lars. Also, Brazil's program has not been able to supply enough fuel and
in order to meet consumer demand, the Brazilian government has been
forced to import ethanol to meet the demand.
REFORMULATED GASOLINE
Reformulated gasoline is an alternative fuel that does not require
engine modifications. It is used mainly because its effectiveness in reduc-
ing tailpipe emissions. Reformulated gasoline was qualified under the
Clean Air Act to compete with other alternatives as an option for meeting
lower emission standards. The formula can vary by region and season,
but reformulated gasoline usually has polluting components like butane,
olefins, and aromatics removed. An octane-enhancer like methyl tertiary
butyl ether (MTBE) has also been added. This can reduce carbon monox-
ide, hydrocarbons and nitrogen oxides and improve combustion efficien-
cy. MTBE was widely used in California, Arizona, and Nevada, but was
phased out after it was found to contaminate water supplies.
ARCO has marketed a reformulated gasoline, EC-1 Regular (emis-
sion control-1), for older vehicles without catalytic converters, in south-
ern California. These older vehicles were only a small segment of the total
car and truck population in the region but produced about a third of the
air pollution. ARCO has also marketed a premium reformulated gasoline,
EC-Premium. The EPA estimated that the ARCO reformulated gasolines
reduced air pollution by almost 150 tons a day in southern California.
NATURAL GAS
Natural gas is found in underground reservoirs and consists mainly
of methane, with smaller amounts of other hydrocarbons such as ethane,
propane, and butane along with inert gases such as carbon dioxide, nitro-
gen, and helium. The composition varies, depending on the region of the
source.
As an engine fuel, natural gas can be used either in a compressed
form as compressed natural gas (CNG) or in a liquid form as liquefied
natural gas (LNG). The major difference between compressed natural gas
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