There are many types of
biomass—organic matter such as plants, residue from agriculture and
forestry, and the organic component of municipal and industrial
wastes—that can now be used to produce fuels, chemicals, and power. Wood
has been used to provide heat for thousands of years. This flexibility has
resulted in increased use of biomass technologies. According to the Energy
Information Administration, 53% of all renewable energy consumed in the
United States was biomass-based in 2007.
Biomass technologies break
down organic matter to release stored energy from the sun.
Biofuels
Biofuels are liquid or gaseous fuels produced from biomass. Most biofuels
are used for transportation, but some are used as fuels to produce
electricity. The expanded use of biofuels offers an array of benefits for
our energy security, economic growth, and environment.
Current biofuels research
focuses on new forms of biofuels such as ethanol and biodiesel, and on
biofuels conversion processes.
Ethanol
Ethanol—an alcohol—is made primarily from the starch in corn grain. It is
most commonly used as an additive to petroleum-based fuels to reduce toxic
air emissions and increase octane. Today, roughly half of the gasoline
sold in the United States includes 5%-10% ethanol.
Biodiesel
Biodiesel use is relatively small, but its benefits to air quality are
dramatic.
Biodiesel is produced
through a process that combines organically-derived oils with alcohol
(ethanol or methanol) in the presence of a catalyst to form ethyl or
methyl ester. The biomass-derived ethyl or methyl esters can be blended
with conventional diesel fuel or used as a neat fuel (100% biodiesel).
Biomass Resources
Biomass resources include any plant-derived organic matter that is
available on a renewable basis. These materials are commonly referred to
as feedstocks.
Biomass Feedstocks
Biomass feedstocks include dedicated energy crops, agricultural crops,
forestry residues, aquatic crops, biomass processing residues, municipal
waste, and animal waste.
Dedicated energy crops
Herbaceous energy crops are perennials that are harvested annually after
taking 2 to 3 years to reach full productivity. These include such grasses
as switchgrass, miscanthus (also known as elephant grass or e-grass),
bamboo, sweet sorghum, tall fescue, kochia, wheatgrass, and others.
Short-rotation woody crops
are fast-growing hardwood trees that are harvested within 5 to 8 years of
planting. These include hybrid poplar, hybrid willow, silver maple,
eastern cottonwood, green ash, black walnut, sweetgum, and sycamore.
Agricultural Crops
Agricultural crops include currently available commodity products such as
cornstarch and corn oil, soybean oil and meal, wheat starch, and vegetable
oils. They generally yield sugars, oils, and extractives, although they
can also be used to produce plastics as well as other chemicals and
products.
Agriculture Crop Residues
Agriculture crop residues include biomass materials, primarily stalks and
leaves, that are not harvested or removed from fields in commercial use.
Examples include corn stover (stalks, leaves, husks, and cobs), wheat
straw, and rice straw. With approximately 80 million acres of corn planted
annually, corn stover is expected to become a major feedstock for biopower
applications.
Forestry Residues
Forestry residues include biomass not harvested or removed from logging
sites in commercial hardwood and softwood stands as well as material
resulting from forest management operations such as pre-commercial
thinning and removal of dead and dying trees.
Aquatic Crops
There are a variety of aquatic biomass resources, such as algae, giant
kelp, other seaweed, and marine microflora.
Biomass Processing Residues
Biomass processing yields byproducts and waste streams that are
collectively called residues and have significant energy potential.
Residues are simple to use because they have already been collected. For
example, the processing of wood for products or pulp produces unused
sawdust, bark, branches, and leaves/needles.
Municipal Waste
Residential, commercial, and institutional post-consumer waste contains a
significant proportion of plant-derived organic material that constitute a
renewable energy resource. Waste paper, cardboard, wood waste, and yard
waste are examples of biomass resources in municipal waste.
Animal Waste
Farms and animal-processing operations create animal wastes that
constitute a complex source of organic materials with environmental
consequences. These wastes can be used to make many products, including
energy.
Some biomass feedstocks,
such as municipal waste, are found throughout the United States. Others,
such as energy crops, are concentrated in the eastern half of the country.
As technologies develop to more efficiently process complex feedstocks,
the biomass resource base will expand.
Biogas
Collecting Gas from Landfills
Landfills can be a source of energy. Organic waste produces a gas called
methane as it decomposes, or rots.
Methane is the same
energy-rich gas that is in natural gas, the fuel sold by natural gas
utility companies. It is colorless and odorless. Natural gas utilities add
an odorant (bad smell) so people can detect seeping gas, but it can be
dangerous to people or the environment. New rules require landfills to
collect methane gas as a pollution and safety measure.
