ENVIRONMENTAL AWARENESS Can the UK meet its AD potential?
Matt Hale, International Sales & Marketing Director, HRS Heat Exchangers
The UK has almost 730 operational anaerobic digestion (AD) plants, with a capacity of more than 2,800 MW of biogas for use as renewable heat, electricity or biomethane (green gas). Here Matt Hale, international sales & marketing director at HRS Heat Exchangers says these figures are impressive but many in the UK biogas believe that the current deployment of AD in the UK is just a fraction of the country’s total potential
Efficient biogas plants are one of the solutions to climate change A
Energy efficient technologies, such as heat exchangers, can improve the performance of AD plants
report commissioned by Cadent Gas Ltd in 2017 concluded that waste feedstocks, (local authority collected waste, commercial & industrial waste, construction
& demolition waste, and sewage sludge) had the potential to generate between 47 and 56 TWh of renewable gas (split between 83% Bio-Synthetic Natural Gas (BioSNG) from gasification and 17% biomethane from anaerobic digestion). The same report also suggested that between 21 and 127 TWh of renewable gas could be generated from non-waste feedstocks (including energy crops, agricultural and forestry residues, manures and other co-products). If we take the most conservative of these
forecasts, using only waste feedstock, then we can see that the total potential for AD in the UK is around 8 TWh of biogas, or 8,000,000 MWh. Based on these figures, current UK capacity is a tiny fraction of the theoretical maximum. We can argue about specific numbers, but there is no doubt that there is still a massive opportunity to boost current AD capacity across the United Kingdom. The Cadent report is not the only source to underline the huge potential of biogas in the UK’s energy mix. The Anaerobic Digestion and Bioresources Association (ADBA) projects that the UK could generate 5.7 billion m3/year of biomethane by 2030, enough to heat 4.5 million
homes. ‘Assuming a conservative improvement in plant efficiency of 25%, these figures could rise to 7.1 billion m3/year, enough to heat 5.5 million homes. With emerging power-to-gas technology, the biomethane potential could increase to 8.0 billion m3/year by adding hydrogen to the AD process to boost the methane content of the biogas generated, equivalent to heating 6.4 million homes. This would deliver a carbon saving of 27.2 million metric tons of CO2 equivalent/year — 6% of the UK’s current annual emissions —specifically within the hardest to decarbonize sectors.’
The benefits of biogas
Anaerobic digestion is unique among the main forms of renewable green energy in that it provides other benefits in addition to the provision of low-carbon energy. It offers a sustainable method for the treatment of organic wastes, and in so doing prevents fugitive carbon emissions from the uncontrolled decomposition of such wastes. AD also produces a nutrient- rich, renewable biofertiliser known as digestate, which can help offset agricultural emissions and improve soil health and organic matter. Not only this, but biogas and biomethane
are uniquely flexible forms of renewable energy. Biogas can be used for heating, or for the generation of electricity via combined heat and power (CHP) units. When upgraded to biomethane, it can be used as a direct replacement for natural gas in the UK gas grid, or as a green transport fuel which is particularly suitable for heavy goods vehicles. These benefits mean that ‘renewable gas can make a significant contribution to meeting 2050 climate change targets, in particular when supporting decarbonisation of the heat and transport sectors, which are currently lagging behind the electricity sector.’
The importance of policy
The importance of supportive policies to drive developments in renewable energy, waste treatment and decarbonisation is well known. In additon, overall energy policy and
26 BUILDING SERVICES & ENVIRONMENTAL ENGINEER NOVEMBER 2023
development needs long term stability and profitability in order to maintain sufficient investment in future infrastructure – and biogas plants are no different.
Over the last 20 years, the AD sector has seen a number of policies designed to promote its development in the UK, including the Renewables Obligation (RO), Renewable Heat Incentive (RHI), Renewable Transport Fuels Obligation (RTFO), Feed in Tariffs (FITs) and Contracts for Difference (CfD). Some of these have been more sucecssful than others, due to numerous factors including the rate of support offered, the period of support provided and the certainty of acceptance into the scheme. Other policies concerning carbon emmissions and waste minimisation have also been important, for example the Climate Change Levy, Emissions Trading Scheme (ETS) and gate fees for waste feedstocks. Following the closure of the RHI, the current support for the AD sector comes in the form of the Green Gas Support Scheme, the UK’s first support scheme created specifically for the AD sector. The GGSS has an annual budget of £150 million.
ADBA analysis of the policy ‘indicates that the GGSS has the potential to support the development of 45-50 new biomethane plants, producing around 2.7 TWh per year. However, much like the RHI, support focuses solely on energy generation, and with the scheme’s 50% waste requirement, the development of projects will depend on the ability to source high biogas yielding waste feedstocks – primarily food waste.’
The need for leadership
While the GGSS is welcome it is currently only scheduled to run until 2025, and food waste collection will not be mandated in England until that date. Furthermore, recent political noises about the perceived impact of the costs of various ‘green’ policies and initatives have created significant uncertainty in the market and among investors. The Powering Up Britain report from the relatively new Department for Energy Security
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