Biofuels

Transportation fuel derived from biological material, or biofuel, is an appealing renewable alternative to fossil fuels. It is sustainable, reduces U.S. dependence on imported oil, and potentially generates lower greenhouse gas (GHG) emissions than fossil fuels. However, its contribution to the nation’s energy inventory will depend greatly on laws and policies, including agricultural practices and subsidies.

The predominant biofuel currently in use is grain-based ethanol, typically made from corn in the United States. It now accounts for about 10% of America’s gasoline supply and will likely maintain that level in the near future under provisions of the federal Renewable Fuel Standard (RFS). However, corn ethanol production requires a large amount of land and water, along with inputs of fertilizers and energy. This results in potential competition with food sources for land use and with other industrial and commercial needs for water. In addition, the current technology is very energy-intensive and much of its energy comes from fossil-fuel-based electricity or heating, offsetting some of the benefit. Some estimates say that it eliminates all the benefit.

Corn ethanol production requires a large amount of land and water, along with inputs of fertilizers and energy.

One analysis cited by the National Research Council found that “Today, if all of the global production of cereal grains were converted to ethanol, leaving nothing for food, the total output would be approximately 14 million barrels of oil equivalent per day. In contrast, current crude oil production is approximately 85 million barrels of oil equivalent per day. Clearly, conventional carbohydrates cannot make a significant impact on the world’s demand for petroleum-based fuels, chemicals, and materials. What can meet that demand is lignocellulose, both from waste and purposefully grown energy crops.”

Moreover, adding ethanol to gasoline reduces the energy content per gallon. According to the U.S. Energy Information Administration (EIA), during the past 20 years, as the percentage of ethanol and other oxygenates increased from 3% to 10% in motor gasoline, the energy content of one gallon dropped 3%.

Very soon, however, the United States—in order to meet its stated renewable-fuel goals—will have to try to develop technology to convert cellulose (as found in wood, grasses, municipal waste, and other non-food sources) into fuel, instead of using corn. The Energy Independence and Security Act of 2007 and the associated RFS stipulate that by 2022 the United States must produce 36 billion gallons of advanced biofuels—about 16 billion of which must come from cellulosic biofuels with life-cycle GHG emissions at least 60% lower than petroleum-based fuel. Meeting this goal will be challenging.

In 2014, the U.S. Department of Energy reported that despite “legislated mandates as part of the federal RFS, there has been very little production of cellulosic ethanol to date. For instance, the legislated RFS target volume for 2013 was 1 billion ethanol-equivalent gallons of cellulosic biofuel, which the Environmental Protection Agency (EPA) reduced to 6 million gallons in August 2013, based on its assessment of supply capacity.” In 2016, final required volumes were reduced from 4.25 billion gallons to 230 million gallons of cellulosic ethanol.

Other technologies readying for deployment beyond 2020 include, among others, algal biodiesel, a fuel produced from algae, and biobutanol, a fuel currently derived from sugars and starches but potentially from cellulosic biomass. Unlike ethanol, which has to be transported by trucks and barges, algal biodiesel and biobutanol—both of which have higher energy content than ethanol—can be transported via existing infrastructure, such as petroleum pipelines. However, significant technical and cost challenges must still be overcome to ensure a major role for either of these biofuels in our energy future.

In any event, the EIA’s 2015 Annual Energy Outlook projects a continued minor role for biofuels during the next 25 years. Their contribution to the total delivered energy consumed in the United States will rise from 0.78 quads in 2015 to 0.84 quads in 2040.