Engie has signed an agreement with Heathrow Airport to replace natural gas with 100 per cent green biomethane from anaerobic digestion to all meter points across all terminals until March 2022.
The energy firm already has an existing partnership to supply biomethane to Heathrow's Energy Centre, as well as natural gas to other areas.
The biomethane is certified under the Renewable Gas Guarantees of Origin (RGGOs) Scheme as being wholly derived from anaerobic digestion.
Heathrow Airport will have the option to buy more green gas if its requirements exceed the estimated consumption over the contract period.
Biomethane will be injected into the grid by a number of producers using a variety of different feedstocks - all within the UK - delivering a number of benefits to Heathrow and the wider environment. These include reduced carbon emissions compared with natural gas, support for local biomethane production sites and support for wildlife at these sites.
In addition, as the gas is produced in the UK, so this supports UK energy resilience with accredited and traceable guarantees of origin and reduces Heathrow's reliance on traditional market routes to source its energy.
Matt Gorman, director of sustainability at Heathrow, said: "The UK aviation industry has made a firm commitment to get to net zero by 2050 at the very latest. On our journey to rapidly decarbonise every aspect of the industry, we are proud to be partnering with Engie to significantly remove carbon from our gas supply, a move that has also helped us to gain carbon-neutral status. We urge other companies to join us in making the switch."