Biofuels
Ag & Energy
|| Biofuels || Renewable
Fuels Standard || Farm Bill || BCO/Pubs ||
Briefings || links
Background:
Biofuels
October, 2003
(Click here for a PDF, printable version of this
document)
Biofuels are renewable fuels derived from agricultural
crops such as corn, sugarcane, and soybeans, or from biomass resources such as
agricultural, wood, animal, and municipal wastes and residues. Ethanol and biodiesel—the predominant
biofuels—can substitute for gasoline and diesel or be blended with them in order to
reduce greenhouse gas emissions, help communities improve air and water quality by
reducing toxins and criteria air pollutants and reusing waste streams, create revenue for
the agriculture sector and support rural economies, and increase energy security.
The use of ethanol
as a transport fuel traces its roots to the 1880’s when Henry Ford built his first
ethanol-fueled automobile, and continued when Ford built the Model-T in 1908 with a
carburetor adjustment that allowed farmers to use ethanol as fuel. Rising taxes on ethanol, combined with a decreasing
price of petroleum and an aggressive campaign run by large oil producers kept ethanol out
of the mainstream.[1] The
use of ethanol as a viable transport fuel was revisited after the oil shortages of the
1970’s sparked interest in domestically produced fuels. UNITED STATES ethanol
production has grown to 2.13 billion gallons in 2002.[2] Today,
ethanol is primarily blended with conventional gasoline in order to extend the volume of
gasoline and as a fuel oxygenate that helps improve air quality.
Rudolf Diesel designed and built the compression
ignition engine or "diesel" engine in the 1890’s. The basic design has
changed little over time. By compressing fuel oil in a chamber, the pressure and
temperature of the oil rise to such a degree that it combusts spontaneously, driving the
engine pistons and moving the vehicle forward. Diesel
engines have been favored for use in buses because they provide the power and fuel
efficiency to carry heavy loads of passengers over long distances. Though diesel engines
have provided enormous benefits to the nation's transportation needs for a long time,
their use has substantial implications for environmental and public health. When
Rudolph Diesel first demonstrated his compression ignition engine in 1898, he used peanut
oil as fuel. Producers continued the use of
vegetable oils in diesel engines, but eventually made a transition to conventional
petroleum diesel because of its relatively lower price, availability, and efficiency.[3] Over
the last few years, interest in biodiesel, which offers many environmental advantages over
conventional diesel, has been growing steadily. Today,
roughly 200 major fleets (public and private) in the United States use biodiesel as
a transportation fuel. Examples of users
include many metropolitan transit systems, school districts, the US military, and
many more. Current dedicated production
capacity is estimated to be between 60 and 80 million gallons per year.[4]
ÞStarched-based
Ethanol is produced by fermenting anddistilling starch crops that have been converted
into simplesugars. In the United States , ethanol is
most often derived from corn that is dedicatedspecifically for ethanol production or from
the biowaste of corngrown for commercial use. Co-products including high proteinanimal
feeds are developed in this process. Ethanol is typically used in blends with
conventionalgasoline at blends of 10% (E10), 85% (E85), and 95% (E95).[5]
[6]
ÞCellulosic ethanolis the same as starch-based ethanolexcept that it is
derived from renewable, essentiallyinexhaustible resources because it utilizes the
cellulose that isfound in all plant matter. Cellulosicethanol can be derived from fast
growing energy crops like willowtrees and switchgrass or from waste products like sugar
canebagasse, rice hulls, orchard prumings, wheat straw, and forestthinnings, municipal
wastes like as waste paper and yard wastes,and industrial wastes such as pulp/paper and
sludge. As with starch-based ethanol, cellulosic ethanol can beblended with gasoline or
used as a pure fuel.
Þ
Biodiesel is a renewable
alternative to conventional diesel. Biodiesel
contains no petroleum, but it can be blended at any level with petroleum diesel to reduce
emissions and improve lubricity. The main
feedstocks for biodiesel are agricultural commodities like soybeans and rapeseed (virgin
oils), or refined cooking oils and unwanted animal fats (non-virgin oils). Making biodiesel is relatively
simple: a fat or oil is reacted with an alcohol (e.g. methanol) in the presence of a
catalyst, and in the process biodiesel and glycerine are produced. Biodiesel
can be used as a full replacement of diesel fuel (B100), but it is most commonly found
mixed at a ratio of 20% biodiesel to 80%normal diesel (B20). At very low blends of 1-2%,
it greatly improves the lubricity of low-sulfur diesel.
|
