There is a very large number appearing increasingly often in discussions about the future of anaerobic digestion in Britain.
64 TWh of biomethane a year by 2050.
The Parliamentary Office of Science and Technology (POST) highlighted this figure in its recent briefing on upscaling anaerobic digestion. One of the National Energy System Operator's Future Energy Scenarios suggests that UK biomethane production could need to reach around 64 TWh annually by 2050.
POST describes that as approximately a tenfold increase from current biomethane production levels.
That sounds like extremely good news for the UK anaerobic digestion industry.
And potentially it is.
But there is a question which I think needs asking before we start mentally filling the British countryside with another generation of digesters:
What are we going to put into them?
Building Digesters Is Only Half the Problem
An anaerobic digestion plant isn't like a wind turbine.
Once a wind turbine has been built, nobody needs to find thousands of tonnes of wind and deliver it to the site every year.
An AD plant is fundamentally different.
Every digester requires a continuing supply of suitable organic feedstock. That supply has to remain available not just when the plant is commissioned, but year after year if the investment is to succeed.
The UK already has hundreds of AD plants competing for food waste, agricultural residues, industrial organic wastes, crops, slurries and other suitable materials.
Expanding biomethane production several times over therefore isn't simply an engineering challenge.
It is a feedstock challenge.
There Is Plenty of Organic Material — But Not All of It Is Available Feedstock
POST notes that the UK produces around 10.2 million tonnes of food waste annually.
England's requirement for separate weekly household food-waste collections should make considerably more source-separated organic material available for treatment, and anaerobic digestion is an obvious destination for much of it.
Agriculture offers further possibilities through manures, slurries, crop residues and other organic materials.
But theoretical quantities should never be confused with economically available feedstock.
Material may be dispersed across too large an area. It may already have another use. Transport may make collection uneconomic. Seasonal availability can create difficulties. Contamination can make apparently attractive waste streams unsuitable.
And where several AD plants are seeking the same material, something else happens:
the feedstock acquires a value.
Competition for Food Waste Is Already Important
This is particularly relevant to food-waste AD.
As more separately collected food waste becomes available under Simpler Recycling, it is tempting to assume that this automatically creates an enormous supply of cheap feedstock for new digesters.
I wouldn't make that assumption.
Established food-waste AD operators already have collection networks, contracts, depackaging systems, tankage and relationships with waste producers.
If new biomethane plants are constructed in the same catchments, competition for dependable feedstock may increase.
A developer therefore needs to know considerably more than how many tonnes of organic waste theoretically arise within 30 miles of a proposed site.
They need to know who controls it, what it currently costs, who else wants it and whether it can realistically be contracted for the life of the project.
I have discussed this problem in more detail here:
Finding the Right Feedstock for Anaerobic Digestion Plants
What About Energy Crops?
Purpose-grown crops can provide predictable feedstock and high biogas yields, which is precisely why crops such as maize became important to parts of the European AD industry.
But increasing their use substantially brings the familiar food-versus-fuel and land-use debate straight back into the discussion.
There are also policy constraints.
The Green Gas Support Scheme requires supported biomethane plants to meet sustainability requirements intended to encourage the use of wastes and residues.
So a theoretical shortage of waste feedstock cannot simply be solved by planting unlimited areas of energy crops.
And Feedstock Isn't the Only Constraint
Even where suitable feedstock can be secured, Britain will not obtain a tenfold increase in biomethane simply by ordering more digesters.
Projects also require suitable sites, planning permission, environmental permits, finance, gas-grid connections or alternative biomethane outlets, digestate storage and dependable agricultural outlets for the resulting nutrients.
Anyone who has developed an AD project will recognise that some of these constraints can take longer to resolve than designing the digester itself.
That is particularly relevant at present because developers are reporting increasing difficulty obtaining planning permission for completely new AD plants on some greenfield and farm locations.
64 TWh Isn't the Only Estimate
There is another important point which can easily disappear when large numbers are quoted.
The 64 TWh figure is a scenario rather than a guaranteed government target.
The UK Government has also referred to its 2023 Biomass Strategy, which estimated around 30–40 TWh of biomethane production by 2050 across its illustrative scenarios.
In September 2026, the Department for Energy Security and Net Zero confirmed that it is considering this evidence while developing future policy for biomethane.
So the precise number remains uncertain.
What seems much less uncertain is the direction of travel: Britain expects biomethane to play a substantially larger role in its future energy system.
The Opportunity Is Real — But So Are the Practical Limits
I remain enthusiastic about the potential for UK biomethane.
It converts organic wastes into useful renewable gas, recycles nutrients through digestate and can make use of much of the country's existing gas infrastructure.
It also offers something increasingly important in a world of volatile international energy markets: domestically produced renewable gas.
I recently looked at that energy-security argument in more detail here:
How UK Biomethane Could Cut Gas Prices and Boost Energy Security
But ambitious biomethane scenarios need to be tested against what can actually be delivered.
That means asking some rather less glamorous questions:
Where is the feedstock?
Who controls it?
How far will it travel?
Where will the digestate go?
Can the project obtain planning permission?
Where will the biomethane be used?
And will the economics still work when competing plants are bidding for the same organic material?
Those questions don't undermine the case for expanding anaerobic digestion.
They are what determine whether that expansion will actually happen.
Steve Last
Chartered Civil & Environmental Engineer (MICE)
Chartered Waste Manager (MCIWM)
Chartered Environmentalist (CEnv)
Sources: Parliamentary Office of Science and Technology, Upscaling Anaerobic Digestion, July 2026; Department for Energy Security and Net Zero, Parliamentary Written Answer on domestic renewable gas production, 7 September 2026.
