Is it worth using biofuels to replace petroleum fuel?
Biofuels, such as corn ethanol and biodiesel, have become a popular topic in the media and among scientists and entrepreneurs. Whereas government mandates increasing use of biofuels for transportation, and farmers and businesses invest to increase production, there is intense discussion among scientists whether biofuels is truly a worthy cause that reduces the net use of nonrenewable energy and lowers carbon emissions. A recent article in Chemical and Engineering News, “The Cost of Biofuels” (C&E News, December 12, 2007, page 12), presented two opposing views. Two more recent articles in Science (Searchinger et al., and Fargione et al., February 7, 2008 issue) that estimate whether increased use of biofuels causes net increase or decrease in greenhouse gas emissions illustrate further how opposite conclusions can be obtained depending on what factors are included in the consideration. For example, if only energy used in the production and processing of corn grain to ethanol is considered, ethanol use results in little or no benefit to carbon emission. Including the animal feed byproducts that are also produced and crediting the energy saved for their substitution of animal feed that otherwise would have been produced, ethanol use results in net reduction in carbon emissions and energy saving. But if increased ethanol production is to be achieved by changing land use, particularly converting forest land, rain forest, and grassland to cropland, the land conversion releases the stored carbon in the soil and diminishes carbon uptake, incurring a carbon debt that takes decades to recover. The argument applies to use of biodiesel as well. In other words, in the short run, the increased use of bioifuels causes a net increase in carbon emission that takes years to recover.
In February, 2008, the students in a class (Sustainability, Technology and Society) taught by Professor Kung were asked to study the C&E News article, then choose two points of argument to analyze to either support or oppose the view of beneficial biofuel usage. Of the 25 students in the class, 19 chose to write opposing arguments, 4 in favor, and 2 undecided. The main points used for opposing arguments include: undesirable land use changes and insufficient fertile land, net energy loss, food-fuel competition leading to higher food prices, net increase in greenhouse gas emission by including NOx emission from fertilizer used and volatile organic compound emission in dry mill processing, and more beneficial use of subsidy for research and development of other technologies.
H. Kung, Feb 19, 2008.