Tech for good

Recycled plastic rocket fuel has lift-off in waste-free space

With carbon dioxide-heavy launches increasing, the space industry needs to improve on its environmental impact. Could rockets use waste plastic for fuel?

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The space rocket was once thought an achievement of human ingenuity so grand that the pollutants it generated were hardly considered. But now we’re seeing several launches a month, their carbon dioxide (CO2) output is adding up.

Scottish space company Skyrora thinks it’s found an answer: A high-grade fuel manufactured from petrochemicals sourced from previously unrecyclable plastics. They believe Ecosene, a fuel similar to kerosene, could disrupt the fossil fuel economy.

Recycling plastics isn’t the solution many of us imagine as we dutifully rinse our milk and shampoo bottles. A paper published in Science Advances estimates we’re recycling less than nine percent of plastic at the end of its life, and encouraging more recycling can’t address the reasons for the low rate of plastic recycling.

In 2015, a paper in the journal Science estimated that up to eight million tons of plastic enter the oceans each year. The Ocean Conservancy calculates seas will contain 250 million tons of plastic by 2030.

A proven eco-fuel

I spoke to Derek Harris, Business Operations Manager at Skyrora. “We need a way to extend the life cycle of plastics – one that doesn’t include burying or burning them,” Harris explains. “We developed the first batch of Ecosene at a small test facility in Slovakia, turning about a ton of unrecyclable plastic into about 600kg of high-performance fuel for rockets or commercial jet aircraft.” That’s enough for an efficient jet to fly over 24,000 passenger kilometers – further than London Heathrow to Auckland, New Zealand.

Skyrora’s engine test using its Ecosene fuel

Skyrora’s aspiration to extend Ecosene’s use from space rockets to commercial jets could multiply its value as a much-needed way for aviation to counter-balance carbon emissions with a different kind of contribution to saving the planet.

To further reduce aviation’s footprint, Skyrora hopes to make a transportable system called a ‘skid’ that allows processing materials to make Ecosene at airports. Making the eco fuel at its site of use would cut another environmental cost of aviation: Transporting fuel from where it’s made to where it’s needed.

Manufacturing innovation meets recycling breakthrough

“We use plastics like polystyrene, polyester and polypropylene that are usually unrecyclable when clean,” Harris clarifies. “Ecosene’s production process means we can even use unclean waste plastics.”

Mixed plastics, some harder to recycle than others, and unclean plastics, are barriers to effective plastic disposal and recycling, which has motivated some countries to burn plastic waste, releasing pollutants into the air.

Being able to use unclean plastics stands this eco-fuel apart as a recycling option. The fuel’s developers have produced plans for marine vehicles that would collect plastic waste from oceans and perform the first step in the Ecosene manufacturing process onboard. The vessels would then transport the waste to nearby facilities for the next steps to convert the plastics to eco-fuel.

Manufacturing petrochemical fuel can produce damaging waste, which Ecosene also addresses. “Processes similar to Ecosene production release harmful gases, but we use these for heating, recycling some of the waste within the manufacturing process.”

Ecosene also contains less sulfur than the form of kerosene rockets use (RP-1 kerosene.) As an atmospheric pollutant, sulfur causes respiratory disease, acid rain and tree and crop damage.

The thinking among Ecosene’s inventors is that reducing environmental impact in the space launch and aviation industries is about willingness to invest rather than technological infeasibility. The technologies exist – companies and investors need to embrace them.

Others have tried to recycle petrochemical plastics into usable fuels before, often failing because it’s hard to extract excess the paraffin waxes manufacture generates. Skyrora’s breakthrough was a low-temperature catalytic pyrolysis process that separates the paraffin waxes, leaving an effective eco-fuel.

Too good to be true?

Ecosene boasts more commercial competitiveness and environmental effectiveness than fuels from other energy companies. Having followed Ecosene’s journey from inception to testing to launch, I had to ask Harris if it was all too good to be true.

He told me, “Before I agreed to take over the Ecosene project from Skyrora, I wanted to see the process working and tested. 21 tests later, including an upper-stage rocket engine for low-earth orbital missions and support, we found Ecosene was one to three percent better than kerosene in energy characteristics. Their claims stood up to scrutiny, and there were signs we could further improve the formula.”

Harris continued, “That said, I wouldn’t claim it’s the ultimate solution to the plastic waste crisis. We must address the climate crisis at source, but in the meantime, we’ve found a strategy to address one of its many symptoms.”

With hydrogen and biofuels on the rise, Ecosene will see its share of competitors. While reliable and designed to address plastics mitigation at its core, Ecosene is still a CO2-producing fuel that can’t contribute to carbon neutrality targets. But hydrogen fuels and engines struggle to produce the power needed for flight: Airbus says their commercial hydrogen jets would be ready to fly around 2035. In the meantime, in rockets and jets, Ecosene makes a compelling replacement for traditional kerosene.

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About authors

Laurence Russell is a technology and culture journalist specializing in space technology, satellite communication and aerospace industries.