Not all biofuels are created equal

As Congress proposes to jumpstart new technologies to generate liquid fuels from renewable biomass feedstocks, it is important that they reward only the best investments, from an energy standpoint and a carbon reduction standpoint. Not all biofuels are created equal. People often generalize about the net energy of biofuels, but in fact there are significant, sometimes dramatic contrasts between particular biofuels.

A comprehensive survey of the research by Argonne National Laboratory, including examination of 22 studies performed over the last two decades, concluded that even though the biofuels production cycle burns fossil fuels in growing, transportation, and manufacture, the end products provide more renewable energy than the amount of fossil fuel energy consumed. Argonne calculated that one unit of corn ethanol energy delivered at the pump requires 0.74 units of fossil energy. By contrast, because energy is needed to process petroleum, it takes 1.23 units of fossil energy to deliver one unit of gasoline at the pump. That makes conventional corn ethanol approximately 60% more efficient from a net energy standpoint than petroleum gasoline. Cellulosic ethanol based on switchgrass has an even better energy balance. Delivering one unit of cellulosic ethanol energy at the pump takes only 0.10 units of fossil energy.
It is also not possible to generalize about conventional ethanol from corn. Newer, more efficient ethanol plants, using wind energy or biomass for process energy would generate much less greenhouse gas and consume far less water than would some of the older plants, or ones using coal to fire the process. Likewise, farming practices for the production of the corn will be a significant factor, or whether the distillers grains byproducts were being dried and shipped, as opposed to onsite consumption of wet grains.

For biodiesel, a comprehensive analysis of lifecycle net energy and greenhouse gas effects was conducted in 1998 in a partnership between the U.S. Dept. of Agriculture and the National Renewable Energy Laboratory. It concludes that biodiesel made from soybeans offers dramatic savings – using 70% less fossil energy than its petroleum counterpart. Again, lower input oilseed crops, grown in conservation rotations with small grains, should produce even better results than fairly intensive soybean farming practices.

? Biodiesel yields 3.2 units of fuel product energy for every unit of fossil energy consumed in its life cycle.
? Biodiesel reduces net emissions of CO2 by 78.45% compared to petroleum diesel. For B20, a blend of 20% B100 and 80% conventional petroleum diesel, CO2 emissions from urban buses drop 15.66%.

In August, 2005, David Morris of the Institute for Local Self-Reliance published a detailed analysis of the biofuels and net energy debate. He made some important points.
Some of the most widely cited studies that show net energy losses for corn ethanol have failed to factor in the energy value of the feed byproducts. They have also stretched far backward in calculating energy inputs, as in, for instance, incorporating the energy inputs in manufacturing the farm equipment and the food eaten by the farmers; but failing to factor into their equations the scrap metal value of the equipment.

The net energy discussion looks backwards, not forwards. Instead of focusing on the efficiencies of the best farmers and the newest facilities and a strategy to make these efficiencies the overall industry and agriculture average, the studies present averages largely reflective of the efficiencies of ethanol facilities that are 20 years old, Morris asserts. In 1980 total energy use was about 69,000 Btus per gallon. Today, those who invest in ethanol facilities can receive performance guarantees from engineering firms for a thermal efficiency in the low 30,000 Btus per gallon and an electricity efficiency of about 0.76 kWh per gallon.

While conventional corn ethanol is not as bad as has been portrayed, it is not the most efficient biofuel product. It is seen by many as an important bridge to more sustainable biofuels, such as cellulosic ethanol and biodiesel.

—Margie MacDonald