Cornflakes and Bioethanol
To continue a series on existing and emerging renewable energy technologies, this article focuses on bioethanol as a renewable alternative to conventional transportation fuels, namely gasoline. Bioethanol offers a path toward reducing our carbon footprint and becoming energy independent, which is great for our economy and national security. Bioethanol is the primary biofuel produced in the United States, which results directly in over 85,000 jobs nationwide according to a report by ABF Economics. Thousands of additional jobs are indirectly supported by the bioethanol industry. Indeed, our state has a bioethanol refinery in Vicksburg, MS operated by Ergon Biofuels with an annual production capacity of nearly 60 million gallons!
Bioethanol is simply ethanol that has been produced from any biomass that can yield fermentable sugars. Yeast can then catalyze the fermentation of these sugars into ethanol, just like making beer or liquor. Through photosynthesis, plants use sunlight to convert carbon dioxide (CO2) into energy-rich chemicals they use to live and grow. These energy-rich chemicals are why biomass, such as wood, even if it’s not processed to make bioethanol, can be burned in a fireplace to release energy to heat your home. This cycle of photosynthetic CO2 fixation into biomass and its combustion to release CO2 is carbon-neutral. In other words, there is no net change in atmospheric CO2 levels because the amount of CO2 released during fermentation and combustion is equivalent to the amount of CO2 captured by the plant. Although it may be counterintuitive, this is why burning one fuel (bioethanol) instead of another fuel (gasoline) can reduce greenhouse gas emissions.
There are a number of pros and cons associated with bioethanol, so let’s start with the advantages. Importantly, it is widely accepted that bioethanol has a positive energy balance after comparing the energy used to cultivate, harvest, and process the biomass to the energy output of the resulting fuel. Studies have found that greenhouse gas emissions can be reduced by 35% to as much as 90% by using bioethanol rather than gasoline. For example, a staggering 37.1% reduction in greenhouse gas emissions can be achieved with ethanol-blended E85 fuel (85% ethanol and 15% gasoline). Notably, E85 still contains some gasoline since pure ethanol is not easily vaporized, which makes it hard to start an engine in cold weather. Greenhouse gas emissions can be reduced by up to 90% when the remaining fibrous material left after bioethanol production is also burned for heat energy resulting in a complete processing of the biomass.
The biggest chemical difference between fossil fuels and bioethanol is oxygen content. Bioethanol is an oxygenated compound with considerably different chemical properties relative to its essentially oxygen free, fossil fuel counterparts. As a result, bioethanol produces cleaner emissions and more efficient combustion in comparison to gasoline, producing only heat, steam, and carbon dioxide. Significantly higher internal pressures can be sustained with bioethanol before pre-detonation occurs, which allows higher compression ratios and shorter burn times. Thus, bioethanol has efficiency advantages over gasoline for the conversion of combustion energy into power. In fact, most gasolines already contain up to 10% ethanol as an additive that serves to promote more complete combustion, which reduces carbon monoxide (CO) and hydrocarbon emissions, in addition to increasing engine torque and power.
So, what are the hidden costs and disadvantages of bioethanol? One major concern with bioethanol is the large amount of farmable land that would be required for large-scale bioethanol production. To put large-scale in perspective, we consume nearly 20 million barrels of oil per day in the United States. Repurposing land for bioethanol production can destroy natural habitats, reduce important biodiversity, and cause other undesirable land changes such as soil erosion and deforestation. Food crops that require high-quality agricultural land for growth are the most commonly used biomass feedstocks for bioethanol production; corn is typically used in the United States. This presents an ethical dilemma associated with reallocating farm land or converting food into transportation fuel. Farmers may be inclined to focus on bioethanol production, which could drive up the cost of food. From cornflakes to high fructose corn syrup, for human consumption or feeding livestock, corn is a staple of our diets.
Economically, bioethanol is more susceptible to price fluctuations based on droughts, crop damage, and its inherent connection to markets, such as food. However, many of these issues are largely avoided by using so-called cellulosic biomass, that is wood, grasses, and other nonedible plant material. The biomass feedstock, conversion process, scale of production, and region have a substantial impact on the cost of biofuels production. In general, bioethanol (i.e. E85 fuel) is moderately more expensive per gasoline gallon equivalent, which takes into account the energy content of the alternative fuel. Bioethanol has a lower energy density than gasoline. On a per volume basis, 34% less energy is released from burning 1 liter of ethanol compared to burning 1 liter of gasoline. For a given vehicle, this means you would need to fill up more frequently when using bioethanol as your primary fuel.
The chemical properties of bioethanol also introduce some drawbacks as it is hygroscopic (absorbs moisture from the air) and miscible with water. Thus, bioethanol is more corrosive than gasoline, increasing the internal wear of electric fuel pumps and engines. However, vehicles with fuel-flex engines, those which can run on E85, are already available from most car manufacturers. Indeed, about half of all new vehicles made by Chrysler, Ford, and General Motors today are flex fuel ready, meaning they can operate on any combination of gasoline and ethanol automatically using an electric sensor that gauges the blend and adjusts the ignition timing as needed. It is important to know what type of fuel your vehicle can handle to avoid damage to the engine as some older cars (typically pre-1986) are unequipped to handle gasoline with even 10% ethanol.
Given the increasing number of fuel-flex vehicles manufactured today, you may own a bioethanol-ready vehicle and not even know it! You can check to see if you have a fuel-flex vehicle (FFV) online at https://www.fuelfreedom.org/our-work/fuels-101/check-car/. The scalability and long term sustainability of bioethanol hinges on economics and exercising good judgement regarding land usage and the interplay between food versus fuel (which can be avoided with a switch to cellulosic biomass). In short, bioethanol is certainly an excellent use of surplus biomass and should be part of an “all-of-the-above” approach to reducing greenhouse gas emissions.
Jonah W. Jurss, Ph.D. is a chemistry professor at the University of Mississippi who does research in the field of renewable energy. He joined the Department of Chemistry and Biochemistry in 2014.