Researchers Seek to Expand Supplies of Clean Aviation Fuels by Producing More from Agricultural Sources

by Tereza Pultarova (Horizon/Tech Xplore) Professor David Chiaramonti is looking down at the ground to help resolve a problem up in the sky: airplanes' emissions of carbon dioxide (CO2) and other pollutants.

An expert in energy systems and power generation at the Polytechnic University of Turin in Italy, Chiaramonti wants land that is unused, marginal and degraded to produce clean fuels for jets.

Oil-rich plants

The fuels would come from oilseed plants such as Camelina sativa—native to Europe and central Asia—and replace kerosene, a fossil fuel that traditionally powers aircraft.

Professor David Chiaramonti is looking down at the ground to help resolve a problem up in the sky: airplanes' emissions of carbon dioxide (CO2) and other pollutants.

An expert in energy systems and power generation at the Polytechnic University of Turin in Italy, Chiaramonti wants land that is unused, marginal and degraded to produce clean fuels for jets.

Oil-rich plants

The fuels would come from oilseed plants such as Camelina sativa—native to Europe and central Asia—and replace kerosene, a fossil fuel that traditionally powers aircraft.

Even as they tested unused land to make HEFA from camelina, the BIO4A researchers advanced traditional production methods.

The project used a refinery that makes HEFA from waste cooking oil and animal fat left over from meat production at a full industrial scale.

This focus explains the participation in the project of two major European oil companies: Total in France and Italy-based Eni.

"We produced 1,000 [metric] tons of HEFA from residual oil, which so far was the largest volume ever produced industrially in Europe in the framework of the EU's research program," Chiaramonti said.

Crop rotation

Back on the unused land, the team was keen to show that producing HEFA from plants like camelina can be done while supporting the cultivation of crops for food and feed.

The idea centers on the use of compost as well as biochar, which is made from plant and animal biomass, improves soil quality and contributes to carbon neutrality or even carbon negativity.

The researchers believe cultivating energy crops could help farmers improve the quality of marginal soil so that biofuels and food production can coexist rather than compete.

Energy markets could pay farmers to restore soil quality with compost and biochar, according to Chiaramonti.

"Then one year the soil can deliver energy crops such as camelina and the next it can grow barley, for example," he said.

Plant residues would be composted and/or turned into biochar by heating at high temperatures and returned to the soil. That would not only improve soil health but also lock in carbon, further decreasing the environmental footprint of the resulting jet fuel.

"We demonstrated that biofuels can be carbon negative," said Chiaramonti. "That's a groundbreaking result."

The researchers tested their approach on plots of degraded land near the Spanish capital Madrid and in the Italian region of Tuscany.

They experimented with different methods of soil recovery and alternately grew barley and camelina, which tolerates drought better than other energy crops and has previously been used to produce HEFA-based jet fuel.

Parallel steps

While degraded land may boost HEFA supplies, many researchers think sustainable jet fuels will in any case have to be made also from more abundant resources like biomass waste that aren't rich in oils.

That's a good deal more complicated than making HEFA from oily biomass and is a challenge being tackled by another research project.

Called HIGFLY, the project lasts for four years until the end of 2024 and is run from Eindhoven University of Technology in the Netherlands.

The researchers are looking at agricultural residues, residues from the food industry and certain types of algae—anything that has sugars in it but isn't edible, according to Dr. Fernanda Neira D'Angelo, the HIGFLY principal investigator who is an expert in chemical engineering at the Dutch university.

Turning sugar-based matter into energy-packed oil that could enable planes to take off involves several steps, according to D'Angelo.

"The process requires much more energy and processing steps than turning oily biomass into HEFA jet fuel," she said.

The researchers are seeking to maximize the efficiency during each step so that most of the biomass and energy used in the process remains in the resulting fuel.

They process the biomass into cyclic organic molecules called furanics and then merge them to produce oils that can be further refined into fuels. The team aims to test initial samples of its biomass-based jet fuel in laboratories within months.

HEFA-based jet fuels currently cost at least twice as much as fossil counterparts. And the price of fuels from biomass waste will be perhaps three times higher.

This mean that making plant-based aviation fuels competitive with fossil jet fuel will require policy changes and more investment in research and development, according to D'Angelo.

"We can make it competitive if we have the investment and the regulation supporting it," she said. READ MORE