Biofuels and the Environment: Taking a Careful Look
Using bio-based wood materials instead of fossil fuels for aviation fuel and valuable co-products sounds like a great idea.
But, will it be environmentally friendly and sustainable?
“The responsibility of the metrics analysis is to ensure that we come up with a bio-based jet fuel industry, where the production throughout the entire supply chain remains sustainable,’’ says Ivan Eastin, professor at University of Washington and director for the Center for International Trade in Forest Products. “The last thing we want to do is to go from a reliance on non-sustainable fossil fuels to developing biofuels that aren’t sustainable.’’
Since the industrial revolution, the increasing use of fossil fuels has led to an increase of heat-trapping carbon dioxide in the atmosphere, which scientists believe is most likely affecting the Earth’s climate. Transportation is the fastest growing contributor of greenhouse gas emissions in the U.S., accounting for about one-fourth of all emissions, and a gallon of fossil-fuel based jet fuel contributes about 20 pounds of carbon dioxide to the atmosphere.
In general, fuels made from biomass should cause less pollution than fossil fuels. Plants and trees absorb carbon dioxide as they grow; when they burn, they simply release the carbon dioxide that was stored while growing. In the long-term, then, they’re not adding carbon dioxide to the atmosphere. Burning fossil fuels, on the other hand, releases carbon that has been stored for millions of years deep in the earth.
"The responsibility of the metrics analysis is to ensure that we come up with a bio-based jet fuel industry, where the production throughout the entire supply chain remains sustainable."
Look a little closer, though, and the environmentally-friendly picture gets cloudier. How much energy is used to extract and haul the biomass to a refinery? How much energy is required to convert this material to the bio-based fuels? How will the use of bio-based fuels affect things like land-use or pollution emissions?
Researchers in the Northwest Advanced Renewables Alliance project will be carefully measuring and studying the environmental impacts of the project to assure the sustainability of a bio-based aviation fuel industry.
The researchers will gather detailed information and identify potential solutions in the following areas:
Life Cycle Analysis
Life cycle analysis is the accounting tool to be used by NARA. The researchers add up all the environmental impacts and energy costs of creating biofuels and co-products from woody biomass “from cradle to grave,’’ says Eastin. They will develop assessments comparing petroleum and bio-based fuels along a variety of environmental attributes, including energy use, greenhouse gas (GHG) emissions, and other environmental measures. The assessments will include a variety of biofuel feedstocks and harvesting options, the bio-jet fuel conversion process, and the impact of the integration of jet fuel manufacturing into existing forest product industries and infrastructure.
The researchers will look at a variety of biofuel and co-products production scenarios and aim to determine potential reductions in greenhouse gas emissions or energy use as well as the economic impacts.
NARA researchers also will be developing biomass supply models and silviculture regimes that will look at the impacts of biomass removal on land productivity and wildlife.
Weyerhaeuser Company has been involved in a long-term coordinated effort across the U.S. and Canada to study the impacts of biomass removal from forests. Weyerhaeuser scientists installed one of the sites in the study over a decade ago in the western U.S. in Washington’s Coast Range. As part of the NARA grant, a similar study will be established in Oregon on forest land that is drier and has more heavily textured soil than the Washington site in order to enhance understanding of the effects across the region.
Working with university and U.S. Forest Service collaborators, the researchers will be studying the impacts of biomass removal on future tree growth and productivity. In the Washington studies, researchers have found a very small decrease in tree growth with the most intensive, extreme removal of biomass, says Greg Johnson, director of forest research at Weyerhaeuser Company, which is coordinating sustainable production efforts.
The researchers will also be looking at the impacts of biomass removal on nutrient and carbon cycles. Using computer modeling, they will be looking at possible effects during the next 50 years.
Air and Water Quality
In addition, the researchers will focus on the potential environmental impacts from land-use change that may occur. Growing a poplar tree plantation for the use of biofuels might contribute positively to reducing carbon dioxide emissions, for instance, but poplar trees are a large, natural emitter of a chemical compound called isoprene, says Brian Lamb, Regents Professor in the WSU Laboratory for Atmospheric Research. In the presence of sunlight and with nitrogen dioxide emissions from such things as smokestacks and automobiles, isoprene combines to form ozone, which could cause pollution problems in the region. It will be important to understand how any land use change associated with the biojet supply chain affects regional air quality and to compare those effects with all of the other air pollution sources that already exist.
The researchers will be looking at the environmental impacts throughout the supply chain, as wood materials make their way from forests to a biorefinery for conversion to an airport. So, for instance, researchers will look at the environmental costs and benefits of transporting wood waste out of the forest. Currently, in forestry operations after trees are harvested, the remaining residues, which include branches, needles, and tree tops, are most often collected into slash piles. Because they are a fire hazard and a natural breeding place for rodents, these slash piles are most often simply burned.
Or, the researchers will assess and compare the different amounts and types of pollutants that might be emitted from a lumber mill, pulp and paper mill, or a biorefinery for the conversion to jet fuel.
“What are the emissions, and will they be different from what’s already being done?’’ says Lamb.