May 23, 2008
FeatureBiofuels of the Future
Switchgrass grown for biofuel production in Nebraska.
Introduction to Biofuels
The growing concern over climate change and greenhouse gases is forcing people to take a hard look at how we produce and use energy. The burning of fossil fuels such as petroleum and coal adds tremendous amounts of carbon dioxide to the atmosphere. Many industrial nations now face the challenge of reducing dependence on oil and coal and finding alternative fuels. One popular alternative fuel is ethanol, a combustible "biofuel" that is produced by the fermentation of plant matter. Nonrenewable fossil fuels form over millions of years from dead organic material. In comparison, biofuels are a renewable resource that are made from recently-harvested organic matter.
Ethanol burns more cleanly than gasoline and coal, producing less carbon dioxide per unit of energy. But some types of ethanol are better than others, and some ways of producing ethanol can cause their own environmental problems.
Biofuels vs. Fossil Fuels
For example, Brazilians are currently producing ethanol from sugarcane, which is easy to grow in Brazil's tropical climate. The problem with this is that areas of the Amazon rain forest are being cut down in order to clear more land for growing sugarcane. The last thing environmentalists want is for the world to lose one of its richest ecosystems—not to mention a large "sink" for carbon dioxide—just to produce a fuel that burns more cleanly than gasoline. A solution to an environmental problem should, ideally, not create another environmental problem.
Costs and Benefits of Biofuels
Scientists at the Smithsonian Tropical Research Institute wanted to weed out less efficient biofuels from more efficient ones. They analyzed the output and environmental costs of 26 different biofuels and how the plants they come from are grown. Biofuels made from Brazilian soybean, Malaysian palm oil, and U.S. corn were found to be worse for the environment than gasoline. The production of biofuel from plant sources such as those requires high energy input and also negatively impacts the environment. Growing and processing corn, for example, requires large amounts of nitrogen fertilizer and diesel fuel to power tractors. Processing the corn into ethanol also requires a lot of energy. The energy output of corn-based ethanol does not make up for the investment of this energy. So while these biofuels are good in that they aren't made from fossil fuels, their use does not combat climate change or environmental degradation.
"Different biofuels vary enormously in how eco-friendly they are," said Dr. William Laurance, one of the Smithsonian scientists who led the study. "We need to be smart and promote the right biofuels, or we won't be helping the environment much at all."
Energy-Efficient Switchgrass
Some biofuels do seem to have a much better ratio of clean energy output to energy and environmental impact. Switchgrass, for example, is native to the U.S. and grows very easily. Under the guidance of the U.S. Department of Agriculture, farmers in North Dakota and Nebraska grew fields of switchgrass and monitored exactly how much energy went into the process. The experiment yielded the kind of result biofuel engineers were hoping for. The estimated energy available from ethanol made from the switchgrass was more than five times the energy that went into its production.
In Nebraska, a technician harvests switchgrass to evaluate yield potential.
The U.S. Department of Energy is now funding the construction of six biofuel refineries that will be able to process cellulosic, or plant-fiber, biofuel materials such as switchgrass, wood chips, sawdust, and other similar products.
"Cost-competitive, energy-responsible cellulosic ethanol made from switchgrass or from forestry waste like sawdust and wood chips requires a more complex refining process but it's worth the investment," notes Samuel Bodman, Secretary of the Department of Energy. "Cellulosic ethanol contains more net energy and emits significantly fewer greenhouse gases than ethanol made from corn."
Switchgrass is also superior to corn and other biofuel sources because its roots remain in the ground after the grass is cut. The roots continue to absorb carbon dioxide and store it in the soil. Corn and wheat roots are only a few feet long, but switchgrass roots can grow as long as eight feet. Scientists estimate that 94 percent of the carbon dioxide emitted into the atmosphere during the cultivation and burning of switchgrass ethanol could be recaptured and stored by the plant. In this way, this plant could be a very efficient and environmentally-friendly source of energy in the future.
More to Explore
- Energy Farming With Switchgrass Saves Carbon
- Biofuels from Switchgrass: Greener Energy Pastures
- Grass Makes Better Ethanol than Corn Does
- Some Biofuels Are Worse Environmentally Than Fossil Fuels, Analysis Shows
What Do You Think?