This post is by guest contributor John Willard.
A biofuel is any type of fuel that results from the biological fixation of carbon. Technically speaking, fossil fuels qualify under this definition because they result from organic matter and millions of years of decomposition. However, biofuels, or “renewable fuels” as they are sometimes called, can be grown as a crop or produced by converting other biomass into a liquid or gaseous fuel. Let’s look at the most popular biofuel in the US, ethanol, and evaluate some of the questions surrounding its sustainability.
Ethanol is the world’s most produced biofuel by volume. In 2011 the US produced 13.9 billion gallons of ethanol, with the majority of the feedstock coming from corn (maize). Ethanol was originally introduced into the gasoline mix to boost oxygen content and to reduce carbon monoxide emissions from combustion. Today, nearly all gasoline in the US is blended to be 10% ethanol, also known as E10. In 2011 ethanol represented 10.6% of gasoline supplies in the U.S.
One of the biggest benefits for ethanol as a vehicle fuel is the relative ease with which it can replace gasoline. You may have heard of “Flex-Fuel” vehicles. These vehicles have been specifically designed to run on E85, an ethanol-gasoline blend that is 85% ethanol. Flex-fuel vehicle owners can switch back and forth seamlessly between E85 and the standard E10 blend that most pumps offer.
Here are a few facts about ethanol:
- Ethanol has 66% of the energy of gasoline by volume (i.e. a gallon of gasoline contains 33% more energy)
- Average price for gallon of E85: $3.47 (national average, October 2012)
- It takes 3 gallons of water to produce one gallon of corn ethanol, excluding irrigation
- E15 has become the primary fuel for NASCAR
- The original Model T Ford ran on ethanol until 1908
As a replacement for petroleum gasoline, ethanol provides significant benefits including reducing the demand for imported oil, improving vehicle emissions, and integrating with the existing infrastructure. However, there are several concerns with the production and use of corn-based ethanol (currently the most widely produced) including carbon dioxide released from production and land-use change, nutrient runoff, and net energy balance. While each of these issues is an area for further research and debate, perhaps the most popular debate is framed around the polarizing “food versus fuel.” In other words, if we are growing corn, shouldn’t we be using it for food instead of for fuel?
The USDA reports that about 40% of all the corn grown in the US is used to produce ethanol. Other major uses of corn include feed and export, shown by the graph below. Food vs. fuel is not a direct tradeoff, however; in the production process of converting corn to ethanol, valuable co-products are produced called Distiller Dried Grains (DDGS) which can be used as animal feed. For each gallon of ethanol produced, approximately 4lbs of DDGS animal feed with three times the protein content of corn are also produced. Still, DDGS can only be fed to livestock in limited quantities in order to avoid nutritional risks. DDGS – and their limitations – complicate the “food versus fuel” debate because, as it turns out, producing corn ethanol provides a little bit of both. To complicate matters further, government subsidies and growing demand for fuel could cause farmers to replace their food crops with fuel crops, putting further pressure on food prices.
Overall, the sustainability of ethanol has shown signs of improvement over the past two decades by reducing the energy required for production, maximizing the use of byproducts, and improving water efficiency. However, despite utilizing 40% of the nation’s most widely produced feed grain, corn ethanol remains a relatively small fraction of overall gasoline consumption. Technological advances, such as producing ethanol from cellulosic material instead of corn, may allow biofuels to overcome many of these sustainability challenges and provide for a more promising renewable fuel future.
The Verdict: After weighing the benefits and drawbacks of corn-based ethanol as a biofuel, it appears to be coming up a bit short. The strain that corn ethanol production places on our agricultural system compared to the relatively small impact it has on fossil fuel use is difficult to justify from an environmental standpoint. Corn-based ethanol may never be a fully sustainable biofuel, but our experience with it provides valuable guidance for developing advanced biofuels that can lead to a more sustainable solution.
John Willard is an alumnus of the University of Washington and the University of Michigan. He currently works as Biosystems Energy Analyst and Project Management Consultant in Ann Arbor, Michigan.