Might jet fuel be produced from human sewage?
A company called Firefly Green Fuels, based in Gloucestershire, is trying to make jet fuel out of human faeces. It is a waste stream that is currently not used, except for as fertiliser for agriculture (which is controversial, due to the danger of a range of chemicals that are not removed from sewage, and microplastic particles). Currently human waste, ie. sewage, breaks down and emits CO2, among other things. If sewage is used to make allegedly low carbon jet fuel, it would need complex treatment requiring a lot of energy, and there would be a further waste product in the end. Such fuels, which could just as well be used for vehicles etc on the ground, as for aviation, would emit just as much CO2 when burned as conventional fuels. Burned in jet engines, it would also produce contrails – which have their own atmospheric heating effect. Supposing jet fuel, or other vehicle fuel, could be produced from human sewage, there might then be a need for another agricultural fertiliser to replace it. The aviation industry is trying to find fuels that it can claim are “low carbon”, if they are produced from carbon that has come from plants or animals – rather than fossil fuels.
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Poop-powered planes: could jet fuel made from sewage take off?
By Nell Lewis, CNN
January 5, 2024
In the race for alternative, sustainable jet fuels, some companies are getting creative. We’ve heard about planes powered with cooking oil, but what about jet fuel made entirely from human poop? Firefly Green Fuels, an aviation company based in Gloucestershire, UK, has created just that – and, unsurprisingly, the prospect of poop-powered planes is attracting attention.
While sustainable aviation fuel (SAF) is not new, the idea of using sewage – an abundant and unavoidable waste – is a novelty. So, could it really be the future of air travel?
Commercial aviation produces about 2.5% of global carbon emissions, contributing to climate change. Efforts to reduce the sector’s impact are underway, with the development of electric and hydrogen-powered planes. But the technology is still a long way off powering long-haul passenger flights. Instead, the industry is looking to use SAF – with the International Air Transport Association (IATA) estimating that it could contribute up to 65% of the reduction in emissions needed for aviation to reach net-zero in 2050.
SAF burns like normal jet fuel and produces the same amount of emissions while a plane is flying, but it has a lower carbon footprint during its entire production cycle, because it’s usually made from plants that have absorbed carbon dioxide (CO2) from the atmosphere when they were alive. Or, in the case of sewage, it’s made from plants and other food that have been eaten by humans and passed through the digestive system. That absorbed CO2 is released back into the atmosphere when the SAF burns, whereas burning jet fuel made from fossil fuels emits carbon that has been locked away.
So far, sewage has been an untapped resource when it comes to SAF, but James Hygate, CEO of Firefly, thinks this is a missed opportunity. “There’s loads of it, it’s everywhere in the world and there’s not really any good use for it at the moment which makes a very low-value material,” he tells CNN.
That’s why the company, a spin-off from Green Fuels, which has been developing low-carbon fuels since the early 2000s, including biodiesel made from rapeseed oil for cars and trucks, turned its hand to jet fuel – and poop.
Processing poop
To turn human waste into a usable fuel, Firefly uses a method called hydrothermal liquefaction, which is good for wet waste. By combining high pressure and heat, it converts the sewage into carbon-rich biochar (a powder that can be used as a crop fertilizer) and crude oil.
So far, production has been on a small scale in a laboratory. But early results have been promising, with independent analysis by researchers in universities in the EU and US finding it almost identical to standard fossil jet fuel. According to a life cycle analysis carried out by Cranfield University in the UK, it also has a 90% lower carbon footprint than standard jet fuel.
Firefly is looking to scale-up production in the coming years. The company expects to submit an application this year for a fuel qualification process with the standards body ASTM International. Then it will start building a processing facility in the UK, which Hygate hopes will be operational before 2030 and capable of handling 100,000 tons of biocrude oil a year – or producing around 40 million liters of SAF. To put that in perspective that’s enough for 800 flights from London to New York, according to Hygate. He adds that it would be more expensive than conventional kerosene used by planes, but cheaper to produce than other biofuels.
Getting hold of the sewage should be straightforward, he says, adding that Firefly is already in talks with a number of UK water utility companies. But he admits that financing the processing facilities could be a challenge. “These are big infrastructure projects that need money behind them to actually come to fruition,” he says. So far, the company received a £2 million ($2.5 million) research grant from the UK Government and a £5 million ($6.3 million) investment from the European airline Wizz Air.
However, the quantity of sewage is one thing that can’t be scaled up. Hygate estimates that if all usable UK sewage waste was put into making aviation fuel, it would still only meet 5% of the UK’s demand for jet fuel. Therefore, it would have to be used alongside other SAF feedstocks, like rapeseed oil.
A 2023 report from the Royal Society on net zero aviation solutions found that “the scale and availability of feedstock” is a restriction for biofuels, and that producing enough to sustain the UK’s aviation demand would require more than half of the country’s agricultural land.
It also noted that there is some debate over whether agricultural waste is really “waste,” since it is often used for animal bedding or feed. Cait Hewitt, policy director at the Aviation Environment Federation, a UK non-profit that monitors aviation’s environmental impact, asks the same question of sewage.
“One of the important questions you need to ask about any form of feedstock for alternative fuels, including waste, is what would have happened to this stuff otherwise?” she says. In the UK, a large quantity of sewage is currently used by farmers as a fertilizer, she adds. If it’s used to make SAF instead, that fertilizer would need to be replaced.
Hygate says that the biochar by-product could be used as an alternative by farmers, although potentially not at the same scale. He adds that there is a possibility that the UK may follow other countries like the Netherlands in banning the spread of sewage on fields. If this happens, the other most common disposal route is incineration, an energy intensive process.
Not to be sniffed at
Despite their limitations, biofuels are likely to play a big part in the future of aviation. The first commercial transatlantic flight powered by 100% SAF, made from waste cooking oils and animal fat, took off from London to New York in November.
Sewage is an interesting potential solution and is not one to be sniffed at, says Hewitt. But she cautions that, as with all SAF, it will still produce the same amount of carbon emissions when the plane is flying, and it doesn’t solve the problem of contrails, which also contribute significantly to the warming created by aviation.
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“To have a chance of getting from where we are today to net zero aviation by 2050, we need to be really focused on genuine, scalable, zero-emission solutions,” she says.
“There might be some limited role for some of these alternative fuels in the short to medium term,” Hewitt adds. “But the big danger is when you hear something like this, it sounds like intuitively such a good idea, and people say, ‘That’s great, we are on the way to sustainable flying, we don’t need to worry about how much we fly.’”
See also
Firm develops jet fuel made entirely from human poo
27 December 2023 (BBC)
By Dave Harvey, Business and Environment Correspondent, BBC West
A new aviation company has developed a type of jet fuel made entirely from human sewage.
Chemists at a lab in Gloucestershire have turned the waste into kerosene.
James Hygate, Firefly Green Fuels CEO, said: “We wanted to find a really low-value feedstock that was highly abundant. And of course poo is abundant.”
Independent tests by international aviation regulators found it was nearly identical to standard fossil jet fuel.
Firefly’s team worked with Cranfield University to examine the fuel’s life cycle carbon impact. It concluded that Firefly’s fuel has a 90% lower carbon footprint than standard jet fuel.
Mr Hygate, who has been developing low-carbon fuels in Gloucestershire for 20 years, said although the new fuel was chemically just like fossil-based kerosene, it “has no fossil carbon, it’s a fossil-free fuel”.
“Of course energy would be used (in production), but when looking at the fuel’s life cycle, a 90% saving is mind-blowing, so yes, we have to use energy but it is much lower compared to the production of fossil fuels,” he added.
Across the world, flying contributes around 2% of global carbon emissions, which contribute to climate change.
It is a small fraction, but growing fast. And taking carbon out of aviation is one of the hardest challenges.
Electric planes are being developed, with a company in the Cotswolds promising hydrogen-electric powered flights for a dozen passengers by 2026.
But it will be years, decades maybe, before mass air travel will be powered by completely new technology.
So finding new, greener ways to make kerosene without using fossil fuels has become a global gold rush.
Dr Sergio Lima
Image caption,
Dr Sergio Lima has made kerosene, right, from sewage sludge, left.
On a small farm in Gloucestershire, Mr Hygate began turning rapeseed oil into ‘bio-diesel’ for cars and trucks 20 years ago.
His company, Green Fuels, now sells equipment to turn cooking oil into biodiesel, and has clients all over the world.
Then he started looking for ways to make green jet fuel. They tried waste oils, waste food, even agricultural scraps. Then they experimented on human waste.
The sewage solids are chemically treated and end up as pure kerosene
He teamed up with a chemist from Imperial College, London, Dr Sergio Lima.
Together, they developed a process which transforms poo into power.
First, they create what they call “bio-crude”.
It looks like oil: thick, black, gloopy. Most importantly, it behaves like crude oil chemically.
Dr Lima, who is also research director at Firefly Green Fuels, said: “What we are producing here is a fuel which is net zero.”
The “bio-crude” acts just like crude oil, and can be converted into kerosene
When Dr Lima first saw the results, he was thrilled.
“This is so exciting because it was produced from a sustainable feedstock, to which all of us are contributing.”
The scientist showed me round his lab, including a mini version of the huge fractional distillation columns that tower over oil refineries.
His one does the same thing. The liquid is heated and then the gases are distilled at precise temperatures to obtain the right ‘cut’ for different fuel.
Drop by drop, a new clear liquid settles in the collection pipes. “This is our bio fuel,” he says with a smile.
Sergio Lima uses a mini version of the distillation columns at oil refineries
“Seeing the final fuel is something amazing.”
The bio-kerosene is now being tested independently at the DLR Institute of Combustion Technology at the German Aerospace Center, working with Washington State University.
Further future testing will also be carried out by the UK SAF (Sustainable Aviation Fuels) clearing House, based at University of Sheffield.
First results have confirmed the fuel has near-identical chemical composition to A1 fossil jet fuel.
The UK Department of Transport has awarded the team a £2m research grant.
Sustainable fuel ‘critical’ to decarbonise aviationSo they can make a test tube of kerosene in the lab.
That is a long way from replacing kerosene in the world’s airports.
Mr Hygate has done his maths. Each human, he calculates, makes enough sewage in a year to produce 4-5 litres of bio jet fuel.
To fly a passenger jet from London to New York would need the annual sewage of 10,000 people.
And another 10,000 to come back.
Put another way, the UK’s total sewage supply would meet about 5% of the country’s total aviation fuel demand.
It may sound small, but he insists: “That’s pretty exciting.”
“There’s a 10% sustainable aviation fuel requirement, that’s a legal mandate. And we could meet half of that with poo.”
They emit the same amount of carbon dioxide from the aircraft, but since the plants that originally made the oil captured CO2 while they grow, experts consider this an 80-90% reduction on fossil fuel carbon emissions.
Environmental campaigners insist that people just need to fly less, and use crops for food or energy production, not making jet fuel.
They are more supportive of the sewage-based fuel, because “human waste is perhaps the one form of rubbish that society really can’t avoid producing”, as Cait Hewitt, policy director of the Aviation Environment Federation put it.
Nonetheless, the International Energy Agency has said Sustainable Aviation Fuels are “critical to decarbonising aviation”.
To show what is possible, Sir Richard Branson recently flew from London to New York on a flight entirely powered by fuel made from waste oils and corn waste products.
But today only 0.1% of aviation fuel is “sustainable”.
Mr Hygate’s target of 5% looks quite big in comparison.
Also he is using a feedstock nobody else wants, but is universal.
“Although it’s been developed here in the south west of the UK,” he says, “it’s a global opportunity”.
The company is now raising funds to build a full-scale demonstrator factory in the UK.
Mr Hygate explained: “The opportunities in very populous cities are enormous. The amount of fuel we can create is huge.”
https://www.bbc.co.uk/news/uk-england-gloucestershire-67771640
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