Plant-Powered Jets Could Reduce CO2 Emissions for Flights and Space Rockets

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Plant-based aviation fuel could offer 10 percent higher density and reduce carbon emissions, particularly when used for long-haul flights or space rockets, according to a new paper.

The paper, published Thursday in the journal Joule, details a method for creating jet fuel from cellulose. This is found in plant cell walls, meaning teams can take plant waste from agriculture and other areas for conversion. The resultant formula has a density 10 percent higher than regular fuel.

“Airplanes consume a lot of fuel during taking off and landing without moving forward,” Ning Li, research scientist at the Dalian Institute of Chemical Physics and an author of the study, tells Inverse. “If we can reduce this (by using the high density aviation fuels which can fly further) and make more direct flights, the CO2 emission will be reduced. For air transportation, if we can let airplanes carry more [people at once], we can also reduce the number of flights. For rockets, if we can send more satellites to space [at once], we can reduce the number of rockets. As a result, the CO2 emission will be reduced as well.”

More efficient fuel means more efficient space rockets.
More efficient fuel means more efficient space rockets.

Biomass-based jet fuels have become a big area of interest in recent years as a means of reducing emissions. Amazon has named it as a key aspect of its plan to reach zero global emissions, while United Airlines agreed in 2016 to buy 15 million gallons of biofuel over a three-year period. Analysis firm Intelligent Partnerhsip counts more than 30 airlines deploying and trialing biofuel.

Aviation could be ideal for a green revolution, as the industry accounts for two percent of global emissions yet it’s expected to double in size over the next 20 years. Biomass also looks more promising than alternatives at this stage, as Tesla CEO Elon Musk claims an electric jet would require a battery of 500 watt-hours per kilogram, around double that of the density found in an electric car. Michael Wolcott, director of Ascent, a federally funded coalition of universities and industry in aviation research, at Washington State University, described alternative jet fuels to GreenBiz as “the one market that has at least a glimmer of light.”

Li estimates that the team’s fuel could be industrialized in the next three to five years. Its benefits will largely focus on long-distance flights and rocket launches, noting that short-haul flights will see limited benefits. Its varying benefits means that it’s hard to place a percentage on exactly how much CO2 it could save. From here, the team aims to remove dichloromethane from the process, an environmentally hazardous solvent normally used in paint remover.

“In this work, we used organic solvent to prevent the formation of humins and restrain the hydrogenation of furan ring during the hydrogenolysis of cellulose,” Li says. “At [present], dichloromethane was found to be the best organic solvent. We are trying to find better solvents.”

Read the paper’s abstract below:

The catalytic conversion of renewable lignocellulose to transportation fuels is crucial to establish energy security and mitigate CO2 emissions. Here, we describe an effective and integrated strategy for the production of high-density aviation fuel with cellulose, an abundant and inedible raw biomass. First, cellulose was selectively converted to 2,5-hexanedione in a separation yield of 71.4%. Subsequently, a mixture of C12 and C18 branched polycycloalkanes was directly obtained in a carbon yield of 74.6% by the aldol condensation/hydrogenation/hydrodeoxygenation reaction of 2,5-hexanedione and hydrogen over a dual-bed catalyst system. The polycycloalkane mixture obtained by this process has high density (0.88 g mL 1) and low freezing point (225 K). In real application, they can be used as advanced aviation fuel or additives to improve the volumetric heat values of conventional aviation fuels.