automobiles. In some foreign countries, such as Brazil, automobiles
operate with 100% alcohol fuel. In the United States, we use a mixture of
alcohol and gasoline, known as gasohol, to fuel some vehicles. Gasohol is
a mixture of unleaded gasoline and ethyl alcohol, or ethanol. Ethanol is
sometimes referred to as grain alcohol. Gasohol does not, however,
provide as much energy per volume as gasoline.
Ethanol
Ethanol is produced from biomass by the conversion process known as
fermentation, similar to the way alcohol made for consumption is
produced. Fermentation involves the decomposition of carbohydrates
found in plants with the production of carbon dioxide (CO2) and acids. An
ethanol plant is a plant where the crops are distilled and processed into
alcohol for use as fuel. The alcohol is then often mixed with gasoline.
Gasohol is used to power many automobiles today. It is a mixture of
approximately 10% ethyl alcohol and 90% gasoline. Ethanol can be refined
from cornstalks and other domestically grown plants.
Methanol
Methanol is a clean-burning liquid. It is also known as methyl alcohol.
Methanol can be made from nonrenewable sources of energy, such as coal,
but it can also be made from renewable sources of energy known as
biomass, such as wood, plants, and manure. It is used as a fuel to power
vehicles. Methanol produces more energy per volume than ethanol.
Therefore, it does not need to be mixed with gasoline to produce good
power. Methanol also burns more slowly than gasoline. The redesign of
engines specifically engineered to run on methanol has given methanol the
ability to produce as much power as gasoline. Because methanol burns
more slowly, it has smoother engine performance than gasoline. Methanol is
being substituted for gasoline in some transportation systems, but a large
infrastructure for the refinement and distribution of methanol is not yet in
place in the United States. Furthermore, the amount of land that would
have to be occupied to harvest plant products specifically for conversion to
methanol would be tremendous, if the United States or any other country
attempted to replace gasoline with methanol on a large-scale basis.
Bioconversion
The process that produces energy from the waste products of our society
is known as bioconversion. The waste is known as biomass. Biomass is
organic material, such as trees, plants, grains, and algae. Wastes, such as
manure, garbage, sewage, and paper, are also sources of biomass. All these
sources of biomass can go through a bioconversion. They can be burned or
converted into alcohols, such as ethanol and methanol. Biomass conversion
can also yield petroleum substitutes and methane gas.
A methane digester converts shredded organic materials into methane
gas that can be used for heating, used for power generation, or purified
and stored for distribution. See Figure 5-7. The type of bioconversion
used by a methane digester is also known as anaerobic digestion, or
decay, which refers to decay without the use of oxygen. A less complex
way of using biomass as an energy source is simply to burn the biomass.
Ethanol: Ethyl
alcohol, sometimes
referred to as grain
alcohol.
Fermentation: The
decomposition of
carbohydrates
found in plants
with the produc-
tion of carbon
dioxide (CO2) and
acids.
Methanol: A clean-
burning liquid
used as fuel to
power vehicles. It
can be made from
nonrenewable
sources of energy,
such as coal, or
from renewable
sources of energy,
such as wood,
plants, and
manure. Methanol
produces more
energy than
ethanol, per
volume, and burns
more slowly than
gasoline.
Methyl alcohol:
See Methanol.
Bioconversion: The
process that
produces energy
from the waste
products of our
society.
Biomass: Waste
products that can
be used in biocon-
version. Examples
are organic mate-
rial (such as trees,
plants, grains, and
algae) and wastes
such as manure,
garbage, sewage,
and paper.
Chapter 5
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