One of the key challenges for the Ministry of Defence (MOD) in going green is making its thousands of suppliers do the same.
Some are already well down that route, including Rolls-Royce, which manufactures the EJ200 engine used to power the Typhoon fighter.
It can already run on a blend of renewable and fossil fuels. Now the company's going further, promising that by the end of this decade, every engine it builds will run solely on sustainable fuels.
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"We have already committed that 70% of our research and development as a company, we are going to spend on de-carbonisation technologies," explained Dave Gordon, Rolls-Royce's UK Director.
"We are having a really good conversation with the RAF about how electric technology could feed into the early trainer aircraft side of things."
The MOD is actually going further. From now on, firms bidding for MOD contracts will be partly assessed on their 'social value' – including their strategy on climate change.
"At least 10% of the weighting of how we evaluate contracts in the future is going to be based on social value," explained Sid Hallam, from Defence, Equipment and Support (DES), the procurement arm of the MOD.
Watch: How the RAF is working to achieve net-zero carbon emissions.
For the UK military, the green agenda is now feeding into every decision it makes.
"There is an argument that says that whoever manages to green their military and defence first, will have first-mover advantage," explained Thammy Evans, a senior fellow from the Atlantic Council GeoTech Center.
"There will be a welcome by people of a military that is able to do that."
The MOD has less than three decades to decarbonise, end emissions and drastically cut the CO2 produced by its aircraft, armour, and vast estate.
Climate change is now seen as a capability issue with the goal of a net-zero UK military now increasingly embedded in the DNA of defence.