Building a green gas future powered by waste

By Charlotte Morton

With the UK’s energy supply accounting for 21% of annual emissions, it is the second largest emitter of greenhouse gases.[1] We will not meet our net zero obligations without urgently curbing these emissions. Green gas is the renewable fuel that can put our net zero responsibilities back on track by decarbonising our homes, workplaces and means of transport.

What do we mean by ‘green gas’?

The term green gas refers to a renewable gas derived from sustainable sources. There are two types of green gas – biomethane and hydrogen.

Biomethane is produced by removing CO2 from biogas – that itself is derived from the breakdown of organic matter such as food scraps and animal waste – and is the main product of anaerobic digestion.

Biogas is passed through an upgrading system, where it is purified to produce biomethane. This is recognised as a carbon neutral gas as the process recycles CO2 that is already in the atmosphere.

Hydrogen, like biomethane, is a potential solution to decarbonising the UK. It is worth noting that there are three types of hydrogen production, but only one can be classified as green.

  • Green hydrogen involves splitting water by electrolysis using a renewable source of energy. It is carbon negative because no carbon is emitted during the process; the by-product is oxygen, which can be released without damaging the atmosphere
  • Blue hydrogen is produced by breaking down natural gas into hydrogen and CO It is designated carbon neutral because it is envisaged the carbon produced will be captured and stored
  • Grey hydrogen follows a similar process to blue hydrogen, but the CO2 is not captured and stored, meaning it is released back into the atmosphere. This is carbon positive and releases just as much carbon into the atmosphere as natural gas, it is not a solution to decarbonising the sector.

Why is AD needed to decarbonise?

Biomethane and hydrogen both provide a route to decarbonisation. However, only biomethane can reduce carbon emissions over the next decade, which is what the IPCC says is required to keep global warming below 2°C, ideally 1.5°C.

For hydrogen to be brought on stream, wholesale infrastructure changes will be required to both the national grid and within every household, which is not achievable in this decade.

Unlike hydrogen, anaerobic digestion is already readily available and compatible with existing infrastructure, making it an ideal interim solution. It also offers the opportunity to create bio-hydrogen, by producing green hydrogen from biogas, making it a great longer-term solution too.

How does the use of waste support a circular economy?

Globally, as humans, we generate 105 billion tonnes of organic waste every year. This is waste which could be recycled through anaerobic digestion (AD) into valuable products such as biomethane and biofertiliser.

AD is win-win-win-win-win, according to the UNFCCC, custodians of the Paris Agreement. With the potential to reduce carbon emissions by 6% by 2030, AD can put the UK back on track to deliver on its carbon budgets and overall target of net zero by 2050. If AD plants are built to the correct standards, they can offer a circular economy, producing renewable energy from waste, creating thousands of skilled jobs across the country and delivering on the government’s levelling up agenda.

Globally, the industry could reduce global emissions by 10% by 2030, while creating between 10 and 15 million jobs. For ‘global Britain’ becoming the world leader in biogas development would pay dividends. What’s not to love?

What needs to happen to unlock a green gas future?

Currently, there is over 140 million tonnes of organic waste produced annually in the UK which is not treated, 65% of which is slurries and manure. Although these organic wastes are low in energy content, they emit high levels of methane, making them damaging to the climate.

Methane is a more potent greenhouse gas (GHG) than CO2, by a factor of 86 over its first 10 years in the atmosphere, and 23 over 100 years. The United Nations say tackling these emissions is the most ‘immediate and cost-effective’ way to deliver the Paris Agreement target to keep global warming below 2°C, ideally 1.5°C – with biogas recognised as a low-cost readily available means of achieving this.

The UK Government at COP26 was among over 100 countries to sign up to the Global Methane Pledge, committing it to reduce methane emissions by 30% against 2020 levels by 2030.

Using these farm wastes as feedstock for AD plants is an easy win since they are already collected on-farm and ready to use. The only thing left to do is to incentivise farmers to recycle waste products through AD.

The UK has policies in place, such as the Green Gas Support Scheme, which is a step in the right direction, but continued government support is needed for the industry to deliver its full potential. It is imperative that the government stops subsidising the fossil fuel industry and further supports the building of AD plants across the UK.

The next eight years will be crucial for shaping the future of our climate and will be our final attempt at stopping the damage done to our planet to date. In the energy sector, using organic waste to produce biomethane will be an essential part of the transition to a green gas future.


For more information on how biomethane and green hydrogen can contribute to a net zero future, check out the ADBA report:

[1] Biomethane andHydrogen: Two green gases, one future | ADBA | Anaerobic Digestion & Bioresources Association (