Office of Energy Efficiency & Renewable Energy

“Witchgrass” Switchgrass: A Feedstock for Future Flights

October 27, 2016

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You might think it would take a Halloween trick to transform grasses, corn husks, and other plants and organic waste into fuel you can use to power your car or an airplane. But scientists are already figuring out how to use chemical processes at a biorefinery to cost-effectively convert the sugars from non-food plants and wastes into biofuel. Biofuels are already powering some airplanes—and that’s no trick!

Biofuel producers are in the process of taking agricultural resources, called biomass (or feedstocks), and transforming them into biofuel. The cost of planting, harvesting, and transporting bioenergy crops and crop wastes can make it hard to lower the cost of biofuel so that it is competitive with petroleum gasoline. However, one tall North American grass—switchgrass—might just have what it takes for a great bioenergy crop.

Switchgrass thrives in many different soil types and land conditions. It can grow with less water than many crops and requires less fertilizer thanks to a deep root system that helps absorb nutrients in the soil efficiently. This combination of benefits makes switchgrass relatively cheap to cultivate and harvest, and makes it beneficial for the environment.

The Energy Department’s Bioenergy Technologies Office (BETO) is working with national laboratories and private industry to cost-effectively harvest and convert switchgrass and other biomass resources into biofuels. These fuels could be used in airplanes or as a direct replacement for gasoline in cars.

For example, in 2015, biotechnology company TennEra completed the development of a cost-effective switchgrass harvesting, transport, and storage system with BETO funding. The system chops switchgrass on the field and transports it in bulk instead of in bales. This process can reduce the cost of switchgrass in the biofuel production process, which can lower the cost of the biofuel.

Another example is the work by researchers at Lawrence Berkeley National Laboratory and the Joint BioEnergy Institute to produce switchgrass-based aviation biofuel. Researchers tested their conversion process using the BETO-funded Advanced Biofuels and Bioproducts Process Demonstration Unit, a Berkeley Laboratory facility that partners with companies to scale-up biofuel technologies. In addition, BETO funded a study at Argonne National Laboratory that examined how growing more switchgrass near freshwater resources can improve water quality by preventing runoff of fertilizers into streams and rivers. 

There are many more reasons to work to commercialize biofuel made from switchgrass:  

  • Planting switchgrass on the margins of croplands reduces soil erosion compared to annual row crops.
  • Switchgrass has a higher tolerance to droughts and floods because its deep roots require less water.
  • Growers can spend less on pesticides because switchgrass has fewer pests.
  • Switchgrass is also very good at storing carbon in soil, which improves soil health.

Switchgrass is one of many “energy crops”—plants grown specifically to be harvested and converted into biofuel at a biorefinery. Growers can cultivate many of these crops on sections of land where other crops cannot grow, making efficient use of land resources and avoiding prime agricultural land so that food can still be grown effectively. Other energy crops include miscanthus, and small, fast-growing trees such as shrub willow, hybrid poplar, and loblolly pine.

The prospects are good for biofuel from switchgrass, not just on Halloween, but all year long!