June 24, 2022  /  News

Anaerobic Digestion and its Role in Combating Climate Change

Climate change that originates from human activity is caused by multiple pollutants, with carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) the largest contributors to global warming. Those three gases are all pollutants caused by agriculture and food production.

However, there are steps farmers and waste managers can take to reduce the amount of ozone-damaging gases they produce. Learning about and investing in anaerobic digestion is an excellent starting point, and here’s why.

What is anaerobic digestion?

Anaerobic digestion is a natural process where bacteria break down organic materials in enclosed spaces without the presence of oxygen. This process takes place in a sealed vessel called a digestor or a reactor. As the organic materials are broken down, biogas is produced, which can then be used as an energy source. 

There are three stages involved in the anaerobic digestion process:

  • The plant or animal matter is decomposed by bacteria.
  • The decomposed matter is first converted into organic acids and then into biogas, which is made up of around 60% methane and 40% carbon dioxide.
  • The biogas and the remaining organic solids and liquids can be used in multiple ways to deliver environmental and economic benefits.

What are the different types of anaerobic digestion?

Several agricultural materials can be processed in a digester:

  • Animal manure – Manure solids can be processed into stable microbial biomass, which can be transported more easily and used for animal bedding or fertiliser for the soil.
  • Food scraps – Food waste is converted into biomethane (biogas) by anaerobic digesters and can power equipment on-site, with surplus energy upgraded to biomethane and sold to the national gas network.
  • Energy crops – Crops including maize, grass silage, energy beet and whole crop cereals can be processed via anaerobic digestion and turned into renewable energy and a bio-fertiliser. Together, they can offset more greenhouse gas emissions than producing compost. 

What are the environmental benefits of anaerobic digestion?

It might seem unlikely that a process that produces methane as a byproduct can be beneficial for the environment, but that’s exactly how anaerobic digestion works. The digester is a controlled environment that can capture the methane produced by the decomposition of organic materials. When used for energy generation, that methane gas can replace power that might have otherwise come from the burning of fossil fuels, making it beneficial for the environment. 

There are also other benefits of anaerobic digestion for farmers, including odour reduction. The biomass produced by the anaerobic digestion process is more stable and contains less volatile odorants than raw manure. It can then be stored and applied to land without creating an odour nuisance for local communities.

Another benefit for farmers and the environment is that plant nutrients are conserved and transformed during anaerobic digestion, producing a nutrient-rich fertiliser that you can apply directly to the soil. That helps farmers negate the cost of manufactured fertilisers and reduces their environmental impact.

Is it worth investing in anaerobic digestion?

As well as the obvious environmental benefits, anaerobic digestion can produce electricity and heat to run localised operations and reduce your energy bills, which is particularly attractive in the current environment of soaring energy costs. Surplus biogas can also be sold to the National Grid, although it must be converted into biomethane, a purified form of biogas containing more than 95% methane, beforehand. 

The Green Gas Support Scheme (GGSS) supports investment in new anaerobic digestion plants that produce biomethane and gives successful applications guaranteed tariffs for 15 years. 

You can also produce high-quality fertiliser from your digestate and even sell your gas to the road fuel market, where, as well as the revenues from the fuel you sell, you’ll also earn Renewable Transport Fuel Certificates (RTFCs). They can be traded to generate more income from the biogas you sell as a transport fuel. 

Here are a few other ways you can make money from your anaerobic digester

The future of anaerobic digestion in farming

Despite the challenges posed by the pandemic, the anaerobic digestion sector still grew by 11% last year, with 63 new plants becoming operational. That took the total number of operational plants in the UK to 642. Of those, 446 are fuelled by farm feedstocks, including food waste, slurry, crops and manure.

The reintroduction of the government’s Green Gas Support Scheme (GGSS) has been eagerly anticipated. It makes the development of larger plants that are capable of producing biomethane for the grid profitable. The high cost of energy also makes smaller AD plants viable for farms with high heat and power requirements, as they can be used to offset the cost of traditional power over several years.

The AD process also removes high-quality carbon dioxide, which you can supply to fizzy drinks companies and other sectors. Alternatively, you can capture the CO2 for long-term storage and generate income in the form of credits and certificates that you can sell to companies that want to offset their carbon footprints. 

Want to know more?

If you’d like to know more about regenerative agriculture and agroecology and discuss the practical steps you can take on your farm, please speak to our experts on 01284 811509 or email office@ojneilcontracting.co.uk today.