Biofuel Must Expand Beyond Ethanol to Address Stubborn Emissions

Nearly a third of CO2 emissions result from high power processes that require some form of combustable fuel, like air travel and long-haul shipping. Advanced biofuels sourced from wastes, residues, and energy crops present a possible solution.

Green energy technology has rapidly developed to reduce greenhouse gas (GHG) emissions from electricity use. A greener grid provides a path for decarbonizing many aspects of daily life through electrification. However, there are many industries vital to modern society that cannot be electrified with current technology. Fossil fuel is required to launch an airplane, power long-haul shipping, and produce steel or cement. These energy-intensive and difficult to electrify industries account for 27% of global CO2 emissions from fossil fuels.

As the world strives to avoid the worst effects of climate change, these emissions will need to be addressed simultaneously. The expansion of biofuel beyond ethanol can decarbonize these industries without disrupting current infrastructure.

According to the 2016 Billion-Ton Report sponsored by the Department of Energy, the United States could sustainably source over a billion dry tons of biomass for biofuel production by 2030, enough biofuel feedstock to cover 30% of peak U.S. petroleum consumption. The report recommends sourcing agricultural and forestry biomass like dedicated energy crops and logging residues. These sources avoid food system stress and reduce GHG emissions from production and transport—issues that limit the long-term viability of first generation corn and soy biofuels.

Despite these limitations, ethanol from cornstarch, which only reduces lifetime fuel emissions by 34%, comprises 14.6 of the 16 billion gallons of biofuel produced annually in the U.S. In contrast, ethanol produced from the leftover leaves, stalks, and cobs can reduce lifetime emissions by 90 to 103%, yet accounts for less than 5% of U.S. annual biofuel production.

Past policy has attempted to advance and diversify biofuels with little success. The Energy Independence and Security Act (2007) set an ambitious production goal of 36 billion gallons of biofuel by 2022, including the unfulfilled provision that only 39% is derived from cornstarch.

The failure to reach these goals reflects the limited development of biofuels that can be used in aircraft and long-haul shipping. These engines cannot run on ethanol, and instead require chemically different fuels derived from feedstock such as soy and canola oil, recycled cooking grease, and some municipal waste. Ethanol can be converted to biodiesel and jet fuel, but more research is required to improve the efficiency of this process.

Past policy has helped create a biofuel supply that is plentiful but unsuitable for reducing stubborn emissions from non-electrifiable transportation and industry. New policy should consolidate available feedstock and incentivize advanced biofuels over traditional ethanol and fossil fuels. Furthermore, policy can no longer set far-off goals reliant on extensive research and development.

While there is exciting research in engineering specialized feedstock, specifically with algae, efforts to scale and commercialize these technologies have stalled. Practical measures must be taken now to source the ample amount of feedstock available across multiple industries.

 Efforts to advance biofuel production have also failed because there is little economic incentive to stray from cornstarch ethanol. The introduction of a carbon tax could change that. Not only would a price on carbon make biofuel more cost competitive with fossil fuels, but it could also motivate biofuel producers to consider the land use emissions of cornstarch ethanol and motivate farmers to cultivate high energy crops like switchgrass, which can be grown on marginalized land to reduce lifecycle GHG by 88%. The carbon tax would also spark innovation in fuel and engine technology to more efficiently incorporate biofuel.

While no emissions are easy to eliminate, long-haul shipping, aviation, and industry emissions are particularly difficult to address because they are currently non-electrifiable. Improving the quality and availability of biofuel would greatly decrease these emissions without a need to completely overhaul existing and established technologies.

Leah Narun

Undergraduate Seminar Fellow
Leah Narun is an undergraduate student studying materials science and engineering in the School of Engineering and Applied Science. Narun was also a Kleinman Center 2020 Undergraduate Student Fellow.