As part of our long-term research program we investigate the economic viability and environmental sustainability of crops that have potential to be grown for cellulosic biofuels such as ethanol. Through our Great Lakes Bioenergy Research Center (GLBRC) sustainability research, which is also conducted in Wisconsin and other parts of Michigan, we seek to answer questions such as:
- At what market price would farmers start to grow crops for cellulosic biofuels?
- How will cellulosic biofuel crops affect habitat for wildlife and beneficial insects, water conservation, and soil quality?
- How much cellulosic ethanol can be produced from various crops?
What is Cellulosic Ethanol?
All biofuels are made from plant material. Cellulosic ethanol is made from the leaves, stems, and other fibrous parts of a plant that have large amounts of cellulose and hemicellulose. Cellulosic ethanol can be made from nonfood plants (such as grass) and has a much greater “energy return on investment” than gasoline or grain-based ethanol, which means it generates far more energy than it takes to produce. Crops grown for cellulosic ethanol production are also referred to as cellulosic or ligno-cellulosic biofuel crops.
Which Crops Can be Grown for Cellulosic Ethanol Production?
Both annual and perennial plants can be used to produce cellulosic ethanol. Annual crops, such as corn, complete their life cycle in one year and therefore need to be replanted every year.
Perennial crops such as hybrid poplar trees can persist after the initial planting for several years or even decades. The primary crops in the Midwestern United States being considered for cellulosic biofuels are:
- Corn cobs and corn stover, the leaves and stalk that remain after grain harvest
- Switchgrass, a perennial grass that was native to the tallgrass prairie
- Miscanthus, a perennial grass native to Asia
- Fast growing hybrid poplar trees
At KBS we are investigating these crops as well as oilseed crops for biodiesel — such as soybeans — and native tallgrass prairie species, such as big bluestem and black-eyed susan.
Why Are We Interested in Making Ethanol from Cellulose?
Currently the main biofuel on the U.S. market is corn grain ethanol, made by using the sugars and starch in corn grain. Both grain-based and cellulosic biofuels can help lessen our use of fossil fuels and can help offset carbon dioxide emissions. However, plants grown for cellulosic ethanol have greater environmental benefits. Cellulose is the most abundant biological material on earth, and using it to produce biofuels can have social and environmental benefits including:
- Reduced competition for land. Using grain to produce biofuels can lead to competition between food and fuel and increase food prices. It can also lead to indirect land use effects, whereby land is cleared elsewhere to replace food-producing cropland now used for biofuel production. In contrast, cellulosic biofuel crops can be grown on lands not suitable for food crops and thereby reduce or avoid food vs. fuel competition as well as indirect land use effects.
- Enhanced ecosystem services. Ecosystem services are the benefits humans receive from ecosystems, including food, fuel, fiber, clean water and air, biodiversity benefits, carbon sequestration, and open spaces. Perennial crops grown for cellulosic ethanol can increase services such as:
- Soil conservation and nitrogen retention because their roots are good at holding soil to prevent erosion and capture dissolved nitrogen before it can contaminate ground and surface water.
- Carbon sequestration below ground in roots and soil organic matter because there is no further tillage after crop establishment.
- Lower fuel and carbon dioxide costs associated with field crop operations such as planting, tillage, and weed control because most crops that would be grown for cellulosic ethanol require much less intensive management than grain crops.
- Diversified agricultural landscapes by allowing farmers to grow a greater variety of crops with more complex mixtures of plant species. For example, a mixture of native grass and tree crops can keep wildlife habitat intact and support vital ecosystem services, including those that help other crops in the landscape.
However, the environmental benefits of cellulosic biofuel crops are not guaranteed. Their environmental success will depend on factors such as which crops are grown, the practices used to manage them, and where in the landscape they are grown.