Five ways anaerobic digestion supports the environment
For the UK to reach its target to become net zero by 2050, it’s crucial we increase our investment in climate positive projects. Anaerobic digestion (AD) goes beyond producing renewable energy. It offers many benefits to the environment too – such as disposing of our waste in an environmentally friendly way, producing organic fertiliser to support UK farmers and creating thousands of local jobs.
Below we discuss five ways in which AD is supporting our environment.
1. AD generates green gas
Biomethane, a green gas, is a product of AD. The process involves breaking down organic matter, such as organic waste and agricultural waste, in the absence of oxygen to produce green gas and digestate.
The resultant green gas – biogas – is purified to produce biomethane which can be readily injected into the UK gas grid. The biomethane molecule is the same as the molecule of natural fossil fuel gas, so it can easily be used as an alternative without requiring any changes to infrastructure.
The increasing need to produce green gas is becoming ever more apparent as we creep closer to the net zero carbon goal by 2050. The use of biomethane and biogas can reduce global greenhouse gas emissions by up to 13%[1], which demonstrates its significance in the renewable energy sector.
2. Producing energy from waste
In 2018, the UK generated 222.2 million tonnes of waste with 50.8 million tonnes of this waste sent to landfill[2]. Organic waste alone accounted for 9.5 million tonnes of waste which released around 36 million tonnes of greenhouse gas emissions, measured in CO2e (carbon dioxide equivalent)[3].
When organic waste rots it produces methane – a potent and damaging greenhouse gas. Greenhouse gases damage the earth’s atmosphere and contribute to climate change, therefore reducing the amount of waste we produce is critical. However, completely avoiding waste isn’t always possible, so ensuring waste is dealt with correctly can reduce the carbon emissions released.
From organic waste to sewage waste, AD plants can process much of the waste which is deposited at landfill sites into climate positive products such as renewable energy.
3. Using digestate as a fertiliser
Not only does AD produce biogas, it also produces a product called digestate, which is the remaining material following the AD process. Digestate has a beneficial use as an organic fertiliser and can be used by farmers just as they would use a ‘bagged’ fertiliser. The difference is that digestate is environmentally sustainable.
Coming in both liquid and solid forms, digestate is packed full of rich nutrients which can be utilised by plants and grass, more so than a raw-slurry fertiliser can offer.
4. A sustainable local source of energy
AD sites which produce biomethane can heat local towns by injecting gas into the existing gas grid. Environmentally conscious consumers can rest easy, knowing their homes are heated with renewable gas. Meanwhile, having multiple AD plants powering communities all over the UK reduces the reliance on international energy sources, which should help stabilise prices long-term.
A local source of gas also means little to no transportation is required, reducing the emissions which are usually produced by transport.
Similarly, emissions from the production and transport of ‘bagged’ fertiliser can be reduced, as farmers choose digestate from a local AD plant as an alternative.
In 2019, 27% of the UK’s total greenhouse gas emissions were generated from transport[4]. Although the transportation of fertiliser and gas only make up a small per cent of that, reducing the need for long-haul transportation of these products is a step in the right direction to tackling the climate crisis.
5. Creating a circular economy
A circular economy is a system which benefits the environment, the community and society as a whole.
By using waste which would otherwise rot at landfill sites to produce renewable energy and organic fertiliser, AD creates a circular economy. There is no reliance on international gas sources and the feedstock for the plants can be locally sourced.
The development and operation of AD plants create jobs for the local community and reduces the carbon emissions produced by those commuting into towns and cities on a daily basis.
By capturing and storing carbon, AD plants can support the carbon cycle and reduce the amount of carbon released back into the atmosphere. Not only that, but the captured carbon becomes a by-product of the AD process and can be sold to the food and drink industry as well as pharmaceutical manufacturers.
AD is a key player in reducing our carbon emissions and with benefits to both the environment and our communities, it is one technology we must be investing in. The UK has set a legally binding target to reach net zero by 2050. Finding solutions to reduce reliance on fossil fuels and cut carbon outputs is key, and the increased use of AD will be required to meet these targets.
[1] https://www.worldbiogasassociation.org/wp-content/uploads/2019/09/WBA-globalreport-56ppa4_digital-Sept-2019.pdf
[2] A review of household behaviour in relation to food waste, recycling, energy use and air travel – Office for National Statistics (ons.gov.uk)
[3] Ibid
[4] Transport and environment statistics: Autumn 2021 – GOV.UK (www.gov.uk)
