New 'wastewater' jet fuel could cut airplane emissions by 70%

A new technology can convert wastewater into biofuel to cut plane emissions by 70% versus conventional jet fuel, scientists say.

Sustainable aviation fuel (SAF) currently makes up less than 1% of the fuel used in the aviation industry, but there is a pressing need to find greener fuel solutions as 2.5% of global carbon dioxide emissions come from aviation.

Mainstream aviation fuel options use oil, while alternative options have relied on fat or grease. In a study published April 25 in the journal ACS Sustainable Chemistry and Engineering, scientists outlined a technology that converts wastewater from breweries and dairy farms into the ingredients needed for SAF — namely volatile fatty acids.

The scientists deployed methane-arrested anaerobic digestion (MAAD) — a process pioneered by Meltem Urgun Demirtas, Argonne National Lab's department manager for Sustainable Materials and Processes. In this process, bacteria, rather than traditional wastewater treatments, break down the organic matter in wastewater via anaerobic digestion, converting the wastewater into butyric acid and lactic acid. These acids could then subsequently be converted into SAF, the scientists said.

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However, the process also produces lactic acids, which limit the production of SAF and even lower its carbon efficiency when being converted from volatile fatty acids into SAF. To get around this, the scientists also created an electrochemical separation method, which extracts organic compounds from wastewater.

The final result was the development of an in-situ product recovery process that removes desired waste in complex mixtures through membrane separation. Coupled with anaerobic digestion, these methods enabled the team to create durable microbial communities that produced a large amount of butyric acid.

Scientists at Argonne National Laboratory will continue working on improving the sustainability of their findings, and even researching other materials from feedstock that could be used with this technology. These efforts were funded by the DOE’s Office of Energy Efficiency and Renewable Energy’s Bioenergy Technologies Office. The hope is that by funding the research efforts, scientists will meet their goal of commercializing the process and scaling it to create sufficient SAF to meet 100% of the demand from the commercial sector.

Scientists have previously highlighted the negative effects of wastewater on ecosystems. Algal blooms that stem from wastewater can "lead to a change in biodiversity," said Anne Jungblut, a life sciences researcher at the National History Museum in the U.K. Changes in biodiversity can trigger harmful consequences for entire rivers.

"Both wastewater streams are rich in organics, and it is carbon-intensive to treat them using traditional wastewater treatment methods," study lead author Taemin Kim, an energy systems analyst at Argonne, said in a statement. "Using our technology, we are not only treating these waste streams but making low-carbon sustainable fuel for the aviation industry.”

The membrane-assisted in-situ product recovery process reduces greenhouse gases by 70% while still being a cost-efficient end product. According to the U.S. Environmental Protection Agency, greenhouse gases cause climate change by containing heat, which causes a ripple effect across various biomes. By reducing them significantly with this process, scientists at Argonne could be taking the first steps to fight against climate change and eliminating the need for harmful fuels.