Tuesday, January 24, 2017

Separating fact from fiction in the newest U.S. federal ethanol study

Debates about the merits of biofuels have been going on for at least a generation. My favorite clip from the early, oil-crisis era ethanol push was Nicholas Wade’s article, "Oil pinch stirs dreams of moonshine travel," published by Science in June 1979. Save for one topic, the terms of the debate — the costs of producing biofuels, whether ethanol took more energy to make than it delivered, the extent to which it really helps energy security, the hope for cellulosic biofuels and the food-versus-fuel dilemma — were the same nearly forty years ago as they are today.

Global warming is the topic not on the table then that is so important now. The effect of biofuels on greenhouse gas (GHG) emissions is the focus of many recent studies. To compare fuels according to their GHG impact, policymakers have adopted a form of computer modeling known as lifecycle analysis (LCA). A new report from the U.S. Department of Agriculture (USDA) is the latest LCA study to claim significant GHG reductions from the use of corn-based ethanol, concluding that it has net GHG emissions 43 percent lower than those of petroleum gasoline. Those results are similar to the findings of lifecycle modeling from Argonne National Laboratory (ANL), on which this latest USDA study heavily relies.

My own work has long come to an opposite conclusion. It shows that the use of biofuels (both ethanol and biodiesel) makes GHG emissions worse that they would otherwise be. This finding is not based on computer modeling, but relies instead on field data to assess the real-world CO2 flows involved when substituting biofuel for fossil fuel.