For a definition of terms commonly used in bioenergy discussions, check out our Glossary.

What is bioenergy?
The term “bioenergy” can be used to describe any energy that is derived from plants and other organic materials. These materials, referred to collectively as biomass, can be burned to generate heat or electricity; fermented to create liquid fuels such as biodiesel and ethanol; or converted into high-value chemical compounds that are used to make polymers and plastics.

Is bioenergy new?
Not at all. Burning wood — which people have done for thousands of years — is a form of bioenergy. The fermentation of plant sugars into alcohol-based fuels dates back more than a century. What is new is the effort to expand the variety of feedstocks that can be harnessed to produce bioenergy. Instead of merely converting corn kernels into ethanol, for example, researchers are now trying to find efficient, economical ways to convert plant materials such as grasses, wood chips, crop residues and even organic components of municipal and industrial waste into energy.

What’s the most common source of bioenergy?
Wood. People use wood and wood products for heat and electricity around the world. In the United States, wood is used to create two percent of the total energy produced. Paper mills and pulp manufacturers commonly use wood chips and pulp waste to provide energy for their plants.

Is ethanol a form of bioenergy?
Ethanol, an alcohol-based fuel commonly derived from plant starches and sugars, is one of the most common and fast-growing forms of bioenergy. Currently, more than 130 biorefineries around the United States make ethanol, producing more than 6.5 billion gallons of ethanol in 2007. The amount of ethanol produced in the United States has quadrupled since 2000, and ethanol is now commonly used as an additive to petroleum-based gasoline. Worldwide, over 13 billion gallons of ethanol were produced in 2007. More-concentrated biofuels made from ethanol, such as E85, are also increasingly in demand.

In the United States, most ethanol is derived from corn kernels, but in other parts of the world, ethanol is made from sugarcane and crops such as sugar beets. Ethanol can also be made from cellulosic material — the non-digestible parts of plants such as stalks and leaves — although the current processes to do this conversion are inefficient and expensive. Major research efforts are underway to improve these processes.

What are the advantages of making ethanol from cellulose?
Cellulose is the most common organic compound on Earth, and figuring out how to efficiently convert cellulosic material into ethanol would unlock a huge source of renewable energy. Researchers hope to perfect methods that would allow biorefineries to derive ethanol from agricultural residues such as corn stover (the stalks, leaves and husks of the plant), wheat straw, perennial grasses, and wood pulp — materials that have little use or economic value right now and are often discarded as waste. Fast-growing crops such as poplar trees could also be grown as energy crops, reducing the need to rely on things that humans and animals eat for fuel.

What is biodiesel?
Biodiesel is a renewable fuel that can be used instead of diesel fuel made from petroleum. Biodiesel can be made from vegetable oils, animal fats or greases. Most biodiesel today is made from soybean oil. It’s also possible to make biodiesel from used oils or fats, including recycled restaurant grease.

Are biofuels better for the environment than fossil fuels?
Yes. Fossil fuels such as coal and petroleum are derived from organic material that lived millions of years ago. When they are pulled up from underground and burned today, carbon dioxide is released into the atmosphere, one of the major factors believed to cause global warming. Biofuels release carbon dioxide, too, but it’s carbon that was absorbed by the plants that make biofuels as they grew, which means that they aren’t releasing new carbon into the atmosphere. Ethanol also reduces carbon monoxide and other toxic emissions created by burning fossil fuels. Replacing petroleum-based diesel with biodiesel created from the fats and oils in plants results in significant reductions in emissions of carbon dioxide and other pollutants.

Growing, harvesting and processing plants for energy does require energy inputs, such as fertilizer for growing crops, fuel for equipment and water for conversion. Recent studies estimate that the ethanol from corn kernels yields 30 to 50 percent more energy than is required to produce it, a positive net energy balance that continues to improve as ethanol production becomes more efficient. Biodiesel and cellulosic ethanol have even higher net energy balances, which is another reason why many people believe those technologies can augment or supplant ethanol production from corn kernels.

What are the economic advantages of using bioenergy in the place of fossil fuels?
Fossil fuels account for more than 85 percent of energy consumed in the United States each year. To meet its energy needs, the United States must import considerable quantities of petroleum — more than 60 percent of the petroleum used in the nation is imported. Bioenergy can reduce dependence on foreign oil, decreasing the amount of money we spend to import energy and lessening our dependence on politically volatile regions that control a significant share of the world’s crude oil. Producing bioenergy in places where biomass is grown, such as Wisconsin, can create jobs and generate income for local communities. This type of renewable energy builds rural economies and infrastructure for future biofuels. Producing bioenergy in conjunction with animal agriculture can also increase efficiencies and reduce costs for producers and consumers.

Are biofuels economically viable as an alternative to petroleum-based gasoline?
When oil costs $20 a barrel, it can be refined and sold at prices that no biofuel can compete with under present conditions. But with today’s oil prices of over $140 a barrel, some forms of bioenergy are very price competitive. With incentives and farmer subsidies, corn-grain ethanol is economically competitive with gasoline right now. Using current technologies, cellulosic ethanol cannot compete on price with gasoline, but most analysts expect the cost of refinement to come down with improved technologies.

Can biofuels replace petroleum-based gasoline?
Given the U.S. consumption of gasoline, it’s not likely that biofuels will ever fully replace petroleum-based gasoline. Currently, around a quarter of the United States’ corn crop goes to the production of ethanol, yet ethanol still constitutes only about two percent of the country’s overall consumption of transportation fuel. Scientists estimate that even if the entire U.S. corn yield were used to make ethanol, it would satisfy only about 10 percent of our vehicle needs.

Cellulosic ethanol would improve the situation. The Department of Energy has estimated that there are more than one billion tons of excess biomass produced in the United States each year, which, if converted to ethanol, could supplant more than 30 percent of the nation’s petroleum consumption. Still although they have enormous potential, biofuels should be considered one piece of a larger strategy — along with conservation, increased energy efficiency of vehicles, and continued expansion of other renewable energy sources — to reduce dependence on non-renewable, non-sustainable energy sources.