Biogas—also known as biomethane, swamp gas, landfill gas, or
digester gas—is the gaseous product of anaerobic digestion (decomposition
without oxygen) of organic matter. In addition to providing electricity and
heat, biogas is useful as a vehicle fuel. When processed to purity standards,
biogas is called renewable natural gas and can substitute for natural gas as an
alternative fuel for natural gas vehicles.
Biogas is usually 50% to 80% methane and 20% to 50% carbon
dioxide with traces of gases such as hydrogen, carbon monoxide, and nitrogen.
In contrast, natural gas is usually more than 70% methane with most of the rest
being other hydrocarbons (such as propane and butane) and traces of carbon
dioxide and other contaminants.
More than half the gas used in Sweden's 11,500 natural gas
vehicles is biogas. Germany and Austria are targeting 20% biogas in natural gas
vehicle fuel. In the United States, biogas vehicle activities have been on a
smaller scale.
Production
Biogas is a product of decomposing organic matter, such as
sewage, animal byproducts, and agricultural, industrial, and municipal solid
waste. Biogas must be upgraded to a purity standard to fuel vehicles and be
distributed via the existing natural gas grid.
Biogas from Landfills
Landfills are the third-largest source of human-related
methane emissions in the United States. Methane can be captured from landfills
and used to produce biogas. Methane gas collection is practical for landfills
at least 40 feet deep with at least 1 million tons of waste.
Find examples of landfills using biogas for vehicle fuel
from the Sanitation Districts of Los Angeles County.
Biogas from Livestock Operations
Biogas recovery systems at livestock operations caewable energy in cost-effective ways. Animal manure can be collected and
delivered to an anaerobic digester to stabilize and optimize methane
production. The resulting biogas can be used to fuel natural gas vehicles.
The U.S. Environmental Protection Agency (EPA) estimates 8,200
U.S. dairy and swine operations could support biogas recovery systems with the
potential to generate more than 13 million megawatt-hours and displace about
1,670 megawatts of fossil fuel-fired generation collectively per year. Biogas
recovery systems are also feasible at some poultry operations.
An example of converting livestock manure to biogas to fuel
vehicles is the Western United Resource Development project.
Distribution
After biogas is produced, it must be refined for pipeline
distribution to use as a vehicle fuel. Refining biogas means increasing the
proportion of methane and decreasing the proportion of carbon dioxide and
contaminants through absorption, adsorption, membrane separation, or cryogenic
separation.
Renewable natural gas can be distributed via existing
natural gas distribution routes. Because these technologies are not developed
and tested fully yet, distributing renewable natural gas via the pipeline grid
is not common practice.
Benefits
Benefits
Biogas can be an alternative to conventional transportation
fuels. The benefits of biogas are similar to the benefits of natural gas.
Additional benefits include:
Increased Energy
Security—Biogas offsets non-renewable resources, such as coal, oil, and
fossil fuel-derived natural gas. Producing biogas creates U.S. jobs and
benefits local economies.
Fewer Emissions—Biogas
reduces emissions by preventing methane release in the atmosphere. Methane is
21 times stronger than carbon dioxide as a greenhouse gas.
Better Economics—Biogas
reduces the cost of complying with EPA combustion requirements for landfill
gas.
Cleaner Environment—Producing
biogas through anaerobic digestion reduces landfill waste and odors, produces
nutrient-rich liquid fertilizer, and requires less land than aerobic
composting.
Research and
Development
Research and development efforts are reducing the costs of
biogas production and purification, producing higher-quality natural gas from
biogas, and evaluating the performance of biogas-fueled vehicles. Some federal
and state programs assist in these efforts, including EPA's Landfill Methane
Outreach Program and AgSTAR Program. Learn more about landfill gas research and
development projects from the Natural Gas Vehicle Technology Forum.
Since small scale units can be relatively simple to build
and operate biogas should be used directly if possible (for cooking, heating,
lighting and absorption refrigeration), since both electricity generation and
compression of gas (for storage or use in vehicles) use large amounts of energy
for a small output of useful energy. This concept is suited to
"distributed" systems where waste is treated near the source, and
sludge is also reused locally, to minimise transport and initial capital cost
compared to a "centralised" system. As the distributed system will
need a support network biogas contributes to the "triple bottom
line"; benefiting the environment, reducing costs and contributing to the
social structure.
Basic Biogas provides some introductory material, the Safety
page provides some important information, Science Fair Projects and the Poly Digester
pages give ideas about smaller projects and Anaerobic Digestion gives a bit
more detail and information about larger projects. If you still have unanswered
questions the volunteer members of the Expert Panel will try to assist.There
are also more links here.
There is a Biogas Course in Germany in September (presented
in English) or you can look at an Introductory Biogas Online Course.
You may like to visit the Biogas Wiki, which includes a list
of National/Regional Associations. If you want to add information related to
biogas the wiki is easy to edit with a menu like in Word! Note that you will
have to join Wikispaces, for free, and request membership if you want to
contribute more than Comments.
