5 September 2023

Anaerobic digestion

Almost a decade ago, it was reported that the UK had doubled its anaerobic digestion (AD) capacity between 2010 and 2014, saving five million tonnes of CO2.

The figures were provided by the Anaerobic Digestion and Biogas Association (ADBA), which believes that its work will help ‘pave the way for a carbon-free future’.

So where are we now? If anaerobic digestion and biogas hold such potential in helping us to decarbonise, are we doing enough to maximise on that, and is biogas in fact crucial to helping our nation achieve its net zero ambitions? Here, we have a look at some of the ways biogas could be used to help transform the energy system, and what the future holds for AD, biogas and biomethane.


How could anaerobic digestion help us get to net zero?

The UK has taken significant steps forward in decarbonising energy, but while renewable power capacity has reached record levels, accounting for 40% of all electricity generation during 2022 according to the World Economic Forum, our power system still remains reliant on natural gas. In June 2023, National Grid ESO reported that 37% of electricity was generated by gas.

Add to this the challenge of decarbonising heat for our homes and industries, and it’s easy to see that the net zero conversation has possibly been too exclusively focused on renewable power. Thankfully, policymakers are now beginning to consider the crucial role greener gases can play.

AD offers a secure, local and reliable source of energy generation which looks likely to become an important part of the UK’s energy mix over the coming years. ABDA believes it could supply up to 30% of UK’s domestic gas demand by 2030, dramatically reducing our reliance on imported gas and helping to lower energy prices as well as carbon emissions.

The AD process turns organic matter, such as food and agricultural waste, into low carbon biogas. This can then be used for electricity generation in place of CO2 emitting natural gas, or can be upgraded to zero-carbon biomethane and injected into the gas grid.

Biomethane is indistinguishable from natural gas, and provides a direct substitute for natural gas where decarbonisation is difficult and electrification isn’t an option; in heat-intensive industrial processes for example. It also offers a cost-efficient, scalable way to decarbonise the gas grid without large-scale changes to the infrastructure we currently rely on to heat our homes and power our businesses.


How are we using biomethane now, and what does the future hold?

One of the most common applications of biomethane today is to power commercial truck fleets. During June 2023, biomethane supplier Gasrec reported that demand had reached an all-time high, having increased by 250% from March 2020. With many businesses implementing new sustainability initiatives, and gas-powered trucks increasing in popularity, it’s a trend that’s likely to continue.

The biomethane value chain is less well developed in the energy sector and ABDA states that less than 1% of our nation’s gas supply currently comes from biomethane - but change is on the horizon. On 24th July 2023, Centrica signed a UK biomethane agreement with Yorkshire Water and SGN Commercial Services. The agreement will see SGN develop and operate two biomethane gas-to-grid sites, producing around 125GWh of biomethane each year from the by-products of Yorkshire Water’s sewage treatment processes.

Centrica will offtake the production of green gas, managing shipping, trading and balancing, so that it can be injected into the grid to displace natural gas. It’s a milestone project for Centrica and an important signal that the biomethane economy is growing. When the Energy Networks Association (ENA) published its most recent edition of ‘Britain’s Green Gas Scoreboard’ in December 2022 there were 110 biomethane sites connected to the gas network, with 20 more in plan. It will be good to see how much the tally increases for 2023.


The policy in place to support biomethane production

In our recent blog, The role of biomethane in decarbonising the gas grid, our guest blogger John Baldwin, CEO of CNG services provided some insight into the ways biomethane production could be boosted, to double capacity by 2050. He also explained how the UK Government is already taking action to support the biomethane market, including through the Renewable Transport Fuel obligation (RTFO) and Green Gas Support Scheme (GGSS), which provides tariff support for biomethane produced via anaerobic digestion that can be injected into the gas grid.

The importance of biomethane production across the UK and EU is also highlighted by the REpowerEU plan, which aims to diversify gas supplies and reduce dependence on Russian fossil fuels. The accompanying Staff Working Document published in May 2022 outlined the actions that could be taken to unlock the potential of biogas and biomethane, aiming to, ‘create the preconditions for sustainable upgrading and safe injection of biomethane into the gas grid’. This includes the requirement for countries to segregate organic waste, something not yet mandated in the UK.

The Government food strategy published on 13th June 2022 started to lay the groundwork for better food waste management and mandatory food segregation for all businesses is set to come into force during 2023, with Wales closest to implementing the new rules from October 2023. This will mean more waste making its way to anaerobic digestion rather than incineration or landfill, and an opportunity for new partnerships that turn food waste into valuable energy.


The benefits of adding biomethane to the mix

By diverting food waste from landfill, where it is slowly broken down into methane and carbon-dioxide, and using it to create green energy, the net zero benefits of AD are doubled. And when you combine the AD process with Direct Air Capture (DAC) and Carbon Capture, Utilisation and Storage (CCUS) technologies to give you a potentially carbon-negative process, adding in the fact that the digestate by-product of the process can be used as biofertiliser, the arguments for making AD a central part of our nation’s net zero plans seem obvious. We hope to see an increase in the policy and incentives that support this circular approach.

Getting to net zero by 2050 will mean scaling up green gas production quickly, and it’s not something that will be achievable with any one technology in isolation. We’re going to need to collaborate as an industry, understand each others’ processes better, and form partnerships for the future. A successful biogas economy beautifully complements our growing hydrogen economy; with steam reforming, biogas can be used to produce hydrogen in an inexpensive and environmentally friendly way.

The potential benefits of deploying AD technology, using biogas to generate renewable power and increasing biomethane production are impossible to ignore. While the precise shape our future gas system will take remains uncertain, it seems clear that anaerobic digestion has a central role to play in helping the UK achieve a sustainable, net zero energy future.

Coming soon

Find out more about anaerobic digestion in our next DecarbDiscussions podcast - From waste to energy: the decarbonisation potential of anaerobic digestion with guest Christer Stoyell, Managing Director of Severn Trent Green Power.

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