A Cathay Pacific A350WXB. The plane is partly powered with biofuel on delivery flights.
Cathay Pacific broke new ground when it liked a fuel-from-garbage firm so much that it bought into the company.
Its biofuel manager, Jeff Ovens, says he was presented with a blank canvas in 2009 when the Hong Kong-based airline began looking into new ways of helping to power its fleet.
Back then, a looming European Union emissions trading scheme (ETS) was providing the impetus for airlines to look at what they could do to cut their carbon footprint.
While the ETS was put on ice, within Cathay Pacific there was an acknowledgement that there would be a global scheme covering all airlines - as was signed last year.
Ovens says Cathay developed its own target - carbon-neutral growth from 2020 - and put out feelers for companies making fuels from different kinds of feedstock.
Three years later, it took the unusual step of making an equity investment in United States biofuel developer Fulcrum Bioenergy.
There is also an agreement to take 1.4 billion litres of biofuel over 10 years, starting from 2019, once the manufacturing plant is finished.
"Other airlines were aligning themselves for an offtake agreement and nothing else," says Ovens.
"We wanted to take much more of an active approach, a long game approach."
Fulcrum had run a trial plant in North Carolina to prove its technology, which uses extreme heat to break down municipal waste into basic elements, carbon monoxide and hydrogen, which are then re-formed into a liquid.
Plastics, wood and metal are plucked out for recycling before the remaining largely organic material is processed
Fulcrum has since started developing a production plant in Nevada, not far from Tesla's giant battery factory.
"We can't disclose what we pay, but the price that we've got with Fulcrum is competitive with regular jet fuel," says Ovens.
"The first generation ethanol or biodiesel in Europe had swathes of land dedicated to growing crops - it was not the most [environmentally] sensitive. We didn't want to make the same mistake in an emerging industry - fuel for aviation. Because we had the opportunity of a blank canvas we were very mindful of that from the beginning."
But while Ovens says the agreement means Cathay won't be paying much more than the cost of traditional kerosene, no matter where the price goes, there are limits.
''Trying to convince the leadership that you want to pay more than what you're already paying is a tough call. That is the challenge I have - to go out and find fuel that on an absolute cost base is competitive, or there's a compelling case to pay a little bit more in return for something else.
''Airlines are happy to pay a bit of a premium for small volumes, but not on a long term perpetual basis, it's not going to work. Seed funding is one thing - we'll pay a smidge more, but not long term."
Ovens says that in the long term, there is a limit to the appetite for large volumes of more expensive biofuel.
While he won't disclose the size of Cathay's investment (which includes a board seat), United Airlines has invested US$30 million ($42.7m) in Fulcrum and oil giant BP has also taken a stake.
We can't disclose what we pay, but the price that we've got with Fulcrum is competitive with regular jet fuel.
Cathay is looking for some good news on fuel: huge hedging losses have hit its financial results over the past last three years.
Ovens says there are other parties looking at Fulcrum, which wants to extend its network of collection and refining plants in a country where it is estimated that every citizen produces more than 2kg of rubbish a day.
Worryingly for those in the alternative fuel area, while there is a chunky US federal subsidy for Fulcrum, it is unclear how this may be affected by the Trump Admibistration's policies on energy.
Cathay is also keeping its options open in its quest to arrest its carbon output. It is already using fuel from renewable plant sugars to help power some flights of its newest passenger plane.
Each delivery flight of the new A350-900 aircraft from Airbus in Toulouse uses a 10 per cent blend of biofuel from US firm Amyris. The 12 hour journey from France to Hong Kong is the longest flight to date using a renewable jet fuel.
Ovens says Cathay pays a premium for Amyris product, but it is "part of a learning exercise to get used to the concept of using it in a controlled environment."
He's pragmatic about how far biofuel will go to replace traditional jet fuel.
''Zero carbon is the ultimate holy grail but you've got to be realistic given the resources we have - it would be a great position to be in, knowing that whenever you fly, you're reducing your carbon footprint.
And while passengers are more mindful of their impact on the environment these days, any guilt they feel doesn't make them keen on paying more.
There's no enthusiasm to increase ticket prices. ''It's never been the objective to pass on the premium that we pay."