The US Has "Little to No Chance" of Meeting Its Ethanol Production Targets

As if corn ethanol needed another strike against it, a new study in Environmental Science and Technology takes a look at how climate change will effect corn yields in the US. The results aren't surprising: In the future, we won't be able to grow enough corn to satisfy both our food and fuel demands.

By mid-century, the report concludes, rising temperatures will reduce corn yields by 7 percent on average across the United States, while at the same time increasing irrigation requirements by 9 percent just to keep crop yields at that lower level.

Keep in mind that recent analysis from the US Geological Survey shows that groundwater depletion across the nation—and in particular in some of the most critical areas for growing corn—has occurred at record levels over the first decade of this century. Furthermore, the NOAA projects that climate change will cause some of the same corn-growing areas to become dramatically drier—with current drought conditions in some parts of the country, which began in 1999, becoming permanent.

The reduction in crop yields plus increased irrigation requirements means, the report authors conclude, that the current US target for corn ethanol of 15 billion gallons per year by 2022 has "little to no chance" of being met.

The authors' analysis finds that in order to meet the 15 billion gallons per year target, evaporative water consumption would have to increase 10 percent, with water need for irrigation increasing 19 percent. Each liter of corn ethanol requires 350-1400 liters of water for irrigation, with that same liter of fuel meaning a further 1600 liters of water potentially not directly replenishing the local watershed.

Looking at climate model projections for the next 40 years, the study finds that in the High Plains, increased irrigation requirements will further stress the already stressed Ogallala Aquifer, which provides water for 25 percent of all the grain produced in the nation. However, in areas where precipitation is expected to increase (the blue areas in the map above) this rainfall is expected to come in less frequent but more intense periods, especially during the summer, requiring that greater water storage capability be developed.

Looking at crop yields and climate change more broadly, depending on the degree of warming that actually occurs, corn could take an even bigger hit by 2100. According to research from North Carolina State University, under more moderate warming scenarios US crop yields could decline 30-46 percent by the end of the century, with more extreme warming resulting in crop yield reductions in a genuinely catastrophic range of 63-82 percent. All in all, it means that while we need to find something to replace oil, it's not going to be ethanol.