AskPablo: Corn-Based Ethanol

corn.jpgJason keeps bugging me about my take on the issue of corn-based ethanol. This week I am finally going to take this one on. My gut feel is that it is the devil. Producing an energy-intensive crop that could feed starving people around the world (or at least feed the livestock that will become my next burger) to make a liquid fuel does not make sense to me. Corn farming is notorious for biocide use, genetic engineering, and endless square miles of sterile monoculture. The ammonium nitrate fertilizer, without which corn could not thrive, is a relic of World War II explosives production. This manifestation of the “military-agricultural-industrial complex” is also carbon intensive since it is made from natural gas.


Professor Patzek at Berkeley has long been an opponent of corn-based ethanol. His paper “Thermodynamics of the Corn-Ethanol Biofuel Cycle” is an exhaustive exploration of the energy inputs into the production of corn-based ethanol. Patzek is one of the many people that claim that corn-based ethanol requires more input energy than it yields. This, of course, would mean that our current national excitement about ethanol is completely stupid. If true, does this really mean that we are importing more foreign fossil fuels to make the fertilizer and grow the corn than we actually get out of it?
According to USDA’s Agricultural Economic Report Number 814 “The Energy Balance of Corn Ethanol: An Update” only 17% of the energy used to produce ethanol comes from liquid fuels (gasoline and diesel). This means that for every unit of energy from imported liquid fuel that is used to make fertilizer, grow corn, and make ethanol, we get 6.34 units of energy out. So Patzek is completely wrong? No, this is the conversion rate from liquid fossil fuels to ethanol, but what about natural gas?
When you take into account the massive quantities of natural gas that are consumed to produce the ammonium nitrate fertilizer the conversion ration drops to 1.34. This means that we get a little bit more out than we put in, but no where near as impressive as one would expect based on all the hype. Once again proving that “if it sounds too good to be true, it probably isn’t true.” Using different assumptions and a broader system boundary in your analysis you could probably get a result that is less than 1.0, meaning a net negative energy conversion.
How are we going to power our vehicles when oil runs dry or becomes too expensive? The need for a liquid fuel to replace gasoline is clear and the answer does not lie in edible sugar or oil-producing plants, and certainly not in coal-to-liquids. The answer, in my opinion, lies in cellulosic ethanol. Corn stalks, switchgrass, hemp, and forestry waste can all be used to provide a more sustainable liquid fuel source for our thirsty vehicles. The cellulose in this woody biomass can be converted into a gas, and then into a liquid fuel. In fact there are already several working pilot plants producing cellulosic ethanol.
This week I am not going to do any lengthy calculations to prove my point. Others have already done a lot of work on this subject and I have provided several links to their work. Earlier this month the Wuppertal Institute published an interesting paper entitled “Towards a Sustainable Biomass Strategy” with additional insight into the matter. Since this issue is as much political as scientific I look forward to hearing a lively debate in the comment section below. What do you think the future of liquid fuels looks like?
Pablo Päster, MBA
Sustainability Engineer