A UK-based aviation company recently made jet fuel from human poop! So in today’s Finshots, we discuss its sustainability.

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The Story

Taking a flight is convenient for you and me. It could be expensive. But it saves a lot of travel time. But it’s not so convenient for the earth.

Planes actually emit around 20 times as much CO2 per passenger/per km as a train and 4 times as much as a bus. In total they emit around 100 times more CO₂ per hour than a shared bus or train ride. And that could translate into about 1 billion tonnes of CO2 every year or about 4% of human-induced global warming. So if aviation continues to boom, the earth could be 0.1° Celsius warmer by 2050 because of planes alone. Now, that might not seem huge. But let’s put it this way. If aviation were a country instead of an industry, it would be the world’s sixth-biggest emitter after China, the US, India, Russia and Japan! Scary, we know.

So what’s the solution, you ask?

Well, people could fly less for sure. But that could hurt the aviation industry and would be a massive pain for people in general. So maybe Sustainable Aviation Fuel (SAF) is the way to go. To put it another way, we use jet fuel that doesn’t come from non-renewable energy sources like crude oil or refined petroleum. So you could either use food crops such as rapeseed, palm oil, soy and sugar cane to make it. Or alternatively even convert waste into jet fuel ― it could be used cooking oils, municipal sewage or even crop and animal waste. Basically, all of this goes through a rigorous heating process that filters out the oil from dirt and water. Then you throw hydrogen into the mix. And voila! You get SAF.

This is then blended with regular fossil fuels so that it can power planes. It could potentially cut carbon emissions by up to 80%! What’s more? Its chemical composition is a lot like normal jet fuel, making it compatible with engines designed for traditional fuel. So you don’t have to worry about modifying existing plane engines to accommodate SAF.

But as cool as it sounds, here’s the thing. Despite many airlines aspiring to meet 10% of their fuel needs through SAF by 2030, only about 0.1% of it is in use today. And that’s because making SAF comes with its own set of challenges.

To begin with, growing food crops solely for fuel requires vast swathes of land. And that means mass deforestation, displacing biodiversity such as animals and plants already under threat or even indigenous peoples all over the world.

Another concern is that SAF doesn’t come cheap. Until production scales up, SAF could cost two to four times more than the historical average cost of regular jet fuel. A report by consulting firm Bain & Company has proof. It suggests that if the global aviation industry wants to bring down its emissions to almost zero by 2050, it will have to invest close to a whopping $2 trillion. And that’s also because it needs capital to build refineries that will make SAF. It could eat up airlines' razor thin profit margins, while even making ticket prices expensive for flyers.

That’s why researchers are constantly looking for new ways and sources to make SAF with minimal roadblocks. Recently, for instance, Firefly Green Fuels, a UK-based aviation company came up with a way to process human poop into SAF! That’s definitely weird. But it could lower carbon footprint by 90% as compared to standard jet fuel. It’s also may be a solution to a lot of problems SAF production is currently grappling with.

See, we told you earlier that you could need a lot of crops or waste to make sustainable jet fuel. But the thing is that a lot of other industries like the automobile and energy sector have their eyes on these resources to make sustainable fuel too. So you need something that the aviation sector can solely rely on to meet its needs. And human poop could solve that.

For one, it’s available in abundance. And two, flights can save up on money they need to source SAF. Meaning, if they have to lay their hands on crop residue or waste from oils and sewage, they’ll have to spend money to transport these resources from different places. But human poop could be sourced more easily from aircraft and airports, reducing raw material costs.

But before you get too excited about this novel idea, here’s something you might want to know.

See, the International Air Transport Association (IATA) says that it expects to have the capacity to make at least 69 billion litres of SAF by 2028. And to meet such expectations, we’ll need scalable resources. Now, although human poop could be available in plenty, you can't scale production easily. So even if all of the UK’s sewage waste is put into making jet fuel, it would still only meet 5% of the country’s jet fuel requirements. In case you didn’t know, the UK has a legal mandate to meet at least 10% of its jet fuel needs through SAF by 2030. So the other half of its needs have to be sourced from things like cooking oils and crops.

Another problem SAF made from human waste may not solve is contrails. We’re talking about those streaks of white cloud that planes leave behind in clear blue skies when they fly. Actually, a lot of heat is produced from this aesthetic emission. And it also contributes to making temperatures warmer. For context, between 2000 and 2018 contrails created over half of the aviation sector’s warming impact. This was even more than the CO2 emissions from burning the fuel itself. So that’s that.

And finally, SAF from crops could still be more sustainable since plants absorb carbon as they grow. So eventually, they offset the amount of carbon emitted from their use. But humans are carbon emitters. And converting their waste into jet fuel may not really be more sustainable than crops itself.

So yeah, human poop may not be the ultimate solution to all of SAF’s problems, but it’s definitely one of the wheels that can get the SAF truck going.

Until then…

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