In the relentless pursuit of alternative and sustainable aviation fuels, innovative solutions are emerging. While stories of planes powered by cooking oil have captured our imagination, the latest entrant in this field is Firefly Green Fuels, an aviation company based in Gloucestershire, UK, that has successfully developed jet fuel entirely derived from human waste. This groundbreaking initiative has garnered considerable attention, prompting us to explore the viability of poop-powered planes as a potential future for air travel.
Despite the existence of sustainable aviation fuels (SAF), the use of sewage – an abundant and unavoidable waste – presents a novel and intriguing avenue. Given that commercial aviation is responsible for approximately 2.5% of global carbon emissions, contributing to climate change, the aviation industry is actively seeking ways to mitigate its environmental impact. While efforts to develop electric and hydrogen-powered planes are underway, SAF remains a primary focus, with the International Air Transport Association (IATA) estimating it could contribute up to 65% of the necessary emissions reduction for the aviation sector to achieve net-zero by 2050.
SAF shares similarities with traditional jet fuel in terms of combustion and emissions during flight. However, its distinct advantage lies in having a lower carbon footprint throughout its production cycle. Typically derived from plants that absorbed carbon dioxide (CO2) during their growth, SAF counteracts the release of locked-away carbon emitted by burning fossil fuel-based jet fuel. Firefly Green Fuels has innovatively tapped into sewage as an unexplored resource for SAF production, recognizing its global ubiquity and currently underutilized status.
James Hygate, CEO of Firefly, advocates for the untapped potential of sewage as an SAF feedstock, emphasizing its abundance worldwide and the lack of a significant purpose for it. Utilizing a method known as hydrothermal liquefaction, which is particularly effective for wet waste, Firefly converts sewage into carbon-rich biochar and crude oil through a process involving high pressure and heat. While the current production scale is confined to a laboratory setting, preliminary results, backed by independent analysis from EU and US universities, indicate a product nearly identical to standard fossil jet fuel. Additionally, a life cycle analysis conducted by Cranfield University affirms a 90% lower carbon footprint compared to conventional jet fuel.
Firefly Green Fuels is poised to upscale its production, with plans to submit a fuel qualification application to ASTM International this year. The company envisions constructing a processing facility in the UK by 2030, capable of handling 100,000 tons of biocrude oil annually, equivalent to producing approximately 40 million liters of SAF. Although anticipated to be costlier than conventional kerosene, the production cost is expected to be more economical than other biofuels.
While sewage serves as a promising SAF feedstock, challenges arise in scaling up its usage. Hygate acknowledges that utilizing all usable UK sewage waste for aviation fuel would only meet 5% of the country’s jet fuel demand. Consequently, sewage-derived SAF must complement other feedstocks, such as rapeseed oil. The Royal Society’s 2023 report on net-zero aviation solutions underscores the feedstock scale and availability as potential limitations for biofuels, suggesting that meeting the UK’s aviation demand would require over half of the country’s agricultural land.
Cait Hewitt, Policy Director at the Aviation Environment Federation, raises pertinent questions regarding the status of sewage as a feedstock, questioning its alternative uses, such as fertilizer in agriculture. Hygate proposes that the biochar by-product could serve as an alternative for farmers, acknowledging the potential need for a fertilizer replacement if sewage is redirected for SAF production. The evolving regulatory landscape, including the possibility of banning sewage spreading on fields, further adds complexity to the equation, potentially leading to increased reliance on energy-intensive incineration.
In conclusion, Firefly Green Fuels’ pioneering efforts in developing SAF from human waste signal a transformative step in sustainable aviation. While challenges persist in scaling up sewage utilization, the prospect of utilizing abundant and underutilized resources for powering our skies underscores the industry’s commitment to forging innovative paths towards a more environmentally responsible future in air travel.
Visit: Firefly Green Fuels
