Britain's aviation fuel mandate is law. The supply isn't there yet.

Since January 2025, the UK's SAF Mandate has required a growing share of all jet fuel supplied in Britain to be sustainable aviation fuel: 2% at launch, rising to 10% by 2030 and 22% by 2040. It is one of the most demanding decarbonisation obligations placed on any industry, and it is not optional. Suppliers that miss it pay for the shortfall.

The mandate has a design feature most people outside the industry haven't noticed. Nearly all SAF produced today is HEFA fuel, made from used cooking oil and animal fats. Those feedstocks are finite, heavily contested and largely imported, so the mandate deliberately caps the share HEFA can contribute. From the second half of this decade, the obligation can only be met by fuels made another way. That is the gap the policy was written to force open, and it is currently unfilled at anything like the required scale.

Renovare Fuels, a British technology company, is one of the developers building for that gap. Its process takes biogas, the methane produced when organic waste breaks down at anaerobic digestion and waste-treatment sites, and converts it into drop-in liquid fuels: sustainable aviation fuel and renewable diesel that work in today's engines and today's fuelling infrastructure without modification. The feedstock already exists in volume across the UK, much of it currently burned for low-value power or flared, and using it turns a waste-management problem into transport fuel with a fraction of the lifecycle emissions of the fossil equivalent.

The company's technology has moved from laboratory to deployment planning. Renovare is a member of the Renewable Transport Fuel Association, its fuel is certified to the ASTM standard aviation fuel must meet, it is engaged with government on deployment pathways for waste-biogas fuel production, and it has signed its first letter of intent with a UK aviation operator, with further offtake discussions under way. Its first production project is in development, designed to be replicated across the country's existing network of biogas sites.

The commercial logic mirrors the regulatory one. Mandated demand is growing on a published schedule while compliant supply lags years behind, and fuels that qualify under the non-HEFA portion of the obligation command a premium precisely because so few producers can make them. Analysts across the sector have reached the same conclusion: the binding constraint on aviation's energy transition is not demand, and not policy. It is production capacity.

For a country that wrote the mandate, Britain has been slow to build the plants to meet it. The developers who get there first will not struggle to find buyers.