Counting Carbs
"A market for low-carbon fuels can produce a rare convergence of business, agricultural and environmental interests that, if pursued wisely, could represent a "win-win-win" opportunity," promises the report Biofuels: An Important Part of a Low-Carbon Diet, released this month by the Union of Concerned Scientists. But the report says to achieve that goal, we need to "count carbs" accurately, measuring global warming emissions over a transportation fuel’s entire lifetime.
That means the accounting must include how various plants used for biofuels capture carbon dioxide (CO2). It also needs to incorporate the effect of farming practices—the energy consumed, and pollution emitted by farm equipment, fertilizers and tilling practices. Following UCS’s "carb counting" method (taking extraction and related practices into account), liquid coal is shown to increase emissions over gasoline by more than 80 percent. In contrast, cellulosic ethanol—made from woody plants instead of the corn used in conventional ethanol—may be able to reduce emissions more than 85 percent.
"Our current system provides no incentive for fuel providers to accurately measure or minimize their carbon emissions," the report says. "In contrast, a system that requires providers to account for their emissions would spur increased research into life cycle analysis and provide a public process for evaluating the benefits and limitations of different analytical methods."