Everyday, 45,000 planes fly across the United States, carrying some 1.7 million passengers. Aviation dominates a frequent traveler's individual contribution to climate change, and yet is one of the most challenging sectors to decarbonize.
New research published on 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.
"We demonstrate that it is within reach for the United States to decarbonize the fuel used by commercial aviation, without having to wait for electrification of aircraft propulsion," said Nazli Uludere Aragon, co-corresponding author on the study and a recent ASU Geography Ph.D. graduate.
"If we are serious about getting to net zero greenhouse gas emissions, we need to deal with emissions from air travel which are expected to grow under a business-as-usual scenario. Finding alternative, more sustainable liquid fuel sources for aviation is key to this."
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 current way we produce sustainable jet fuel is very land inefficient and not on a large scale," said Nathan Parker, an author on the study and an assistant professor in the School of Sustainability. "There are very limited ways that aviation could become low carbon emitting with a correspondingly low climate impact and this is one way we've shown that is feasible and can get the aviation industry to be carbon neutral through agriculture."
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.
A template for the future
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.
"This was an interdisciplinary team with expertise from ecosystems sciences, climate modeling and atmospheric sciences and economics," said Georgescu, who acknowledged this research was a culmination of eight years of modeling work and collaboration. "To truly address sustainability concerns, you need the expert skills of a spectrum of domains."
"As academics, we should remember economics drives people's decisions on the ground. It is vitally important to find the circumstances when these decisions are also aligned with desirable environmental outcomes."
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