Last summer, President Obama announced that the U.S. Department of Agriculture, Energy and Navy would invest up to $510 million in order to spur the biofuels industry and enhance U.S. energy security. As a result of government support through tax breaks and subsidies, both ethanol and biodiesel have been successfully integrated into the U.S. energy market. However, while biofuels are generally perceived as more “sustainable” than regular gasoline, controversy remains over the environmental costs of their production, as well as their impact on food prices.
At the most basic level, biofuels are simply material from living or recently living organisms that is converted into fuel. Ethanol is derived from the starches and sugars in plants, and biodiesel is derived from sources such as animal fats, vegetable oil, and cooking grease. To reduce emissions of carbon monoxide and other pollutants during fuel burning, ethanol is typically blended with gasoline, and biodiesel is blended with diesel or used in its pure form.
In theory, the carbon emissions released from the burning of biofuels are offset during feedstock cultivation, when the plants photosynthesize carbon dioxide and store it in their biomass. However, the many other phases of the biofuel life cycle—including the farming and refining processes, and the transport of the fuels from producer to consumer—may result in a net increase in greenhouse gas emissions.
Growing ethanol feedstocks such as corn and sugar cane requires huge amounts of land, increasing the global demand on already limited farmland. To boost agricultural productivity, growers apply vast quantities of fertilizer during farming, which releases nitrogen dioxide, a powerful greenhouse gas. Corn, in particular, generally requires more fertilizer than most other biofuel feedstocks.
In light of these and other challenges, including rising food prices, rampant deforestation, and widespread water shortages, biofuel does not appear to be the solution to U.S. energy needs. As ethanol production increases, and as more corn is required for fuel production, it is clear that biofuels in their current form are not a sustainable alternative to fossil fuels. They will only make the country dependent on corn, as it is now dependent on oil.
To address the shortcomings of current biofuel production, scientists are developing new techniques and feedstocks to enhance sustainable production. Switchgrass, a North American perennial tallgrass, sequesters far more carbon dioxide than corn and other row crops, and is drought tolerant, making it a promising alternative feedstock. It requires little fertilization and can grow well on marginal land. Moreover, switchgrass cultivation would not compete with food cultivation, although some farmers may eventually switch to growing switchgrass instead of food crops if it were profitable to do so.
The use of switchgrass for ethanol production is becoming increasingly viable. Until recently, scientists had struggled to release the polysaccharides from the plant’s tough lignin. To reduce these complex carbohydrates into fermentable sugars, researchers introduced a corn gene into switchgrass’s DNA, which increases its starch content, making it easier to extract the sugars.
While this discovery makes switchgrass an appealing alternative to corn, more research is needed before this grassy feedstock will be widely adopted. Switchgrass has been planted in a monoculture for only a few decades, so the long-term effects on land use and carbon sequestration are uncertain. In addition, an energy-using pre-treatment is necessary to efficiently release the polysaccharides. Despite these early uncertainties, switchgrass offers a potentially cheap and efficient way to produce clean fuel for the future.
Another promising biofuel contender is algae, which brings similar benefits to switchgrass in terms of both carbon sequestration and ease of production. Although it is too early to know if biofuel is the sustainable solution to U.S. gasoline demand, the government must support continued scientific and economic research into these and other approaches to sustainable biofuel production.
(Written by Alison Singer, Edited by Antonia Sohns)