The US can meet biojet fuel production demand domestically

The study found that planting the grass miscanthus on 23.2 million hectares of existing marginal agricultural lands – land that often lays fallow or is poor in soil quality – across the United States would provide enough biomass feedstock to meet the liquid fuel demands of the U.S. aviation sector fully from biofuels, an amount expected to reach 30 billion gallons/year by 2040.

Research demonstrates a pathway to sustainably produce biojet fuel domestically and meet the country’s growing aviation fuel demand.

Every day in the United States, 45,000 planes fly across the country carrying some 1.7 million passengers. A frequent traveler’s individual contribution to climate change is dominated by aviation, and yet is one of the most challenging sectors to decarbonize.

The United States is the largest contributor to aviation carbon dioxide emissions in the world. In fact, it is responsible for more than a quarter of all carbon dioxide emitted from flying.

What if we could replace carbon-intensive jet fossil fuels with a cleaner alternative: biojet fuels derived from rain-fed grass grown in the U.S.?

New research that will be published today (November 14) in the journal Nature Sustainability shows a pathway toward full decarbonization of U.S. aviation fuel use by substituting conventional jet fuel with sustainably produced biofuels.

The study, led by a team of Arizona State University researchers, found that planting the grass miscanthus on 23.2 million hectares of existing marginal agricultural lands – land that often lays fallow or is poor in soil quality – across the United States would provide enough biomass feedstock to meet the liquid fuel demands of the U.S. aviation sector fully from biofuels, an amount expected to reach 30 billion gallons/year by 2040.

In the study, the researchers used an integrated framework of land assessments, hydro-climate modeling, ecosystem modeling, and economic modeling to assess where and under what conditions across the United States, energy crops used for biojet fuels could be grown sustainably using criteria that evaluates both environmental and economic performance.

The criteria was extensive. The team first identified and assessed where optimal marginal agriculture lands already existed in the U.S. They then assessed whether or not one could grow the right energy crops on the land without using additional water.

The team then analyzed whether growing energy crop feedstocks on these lands would have detrimental effects on the surrounding climate or soil moisture and predicted the potential productivity of yields of two different grasses – miscanthus and switchgrass – as suitable biomass energy feedstocks. Finally, the team quantified the amount and the cost of biojet fuel that would be produced and distributed nationwide at scale.

The scientists emphasized that this integrated systems perspective was critical to the study. In the past, research around the potential of biofuels has largely consisted of isolated assessments that have not been well-integrated, for example, overlooking key data on how the altering crop cover influences the surrounding climate.

To account for these land-atmosphere interactions, the research team took outputs from their hydroclimate model to inform their ecosystem model. The team then evaluated the economic feasibility for farmers to grow these grasses.

The researchers in their analysis, benchmarked the financial returns of the existing uses for the lands they identified – some already are used for growing corn, soy, or various other crops, and others are being used as pasture – against those from cultivating either miscanthus or switchgrass as biomass feedstock.

Growing miscanthus or switchgrass needed to be more profitable to replace the existing use of the land in each area.

In the end, researchers found miscanthus to be the more promising feedstock, and biojet fuels derived from miscanthus can meet the 30 billion gallons/year target at an average cost of $4.10/gallon.

While this is higher than the average price for conventional jet fuel – typically about $2/gallon – the team concluded it is reasonable when considering biojet’s potential to cut emissions. Notably, in 2022 jet fuel prices have varied from $2 to $5/gallon (not to be confused with retail gasoline) due to changes in supply and demand, showing prices above $4/gallon are well within the range of possibility.

The researchers say that in finding further solutions to the Earth’s climate crisis it is important that the scientific community bridges disciplines and moves past incremental reductions in emissions. Rather, the researchers emphasize the importance of realistic solutions that scale.

Tags: Aviation Sector, Biofuels, Biojet Fuel, US