At Good Energy, the gas we supply is made up of 10% renewable biogas from the UK. This green gas can be used to generate electricity – 32.71% of our renewable electricity fuel mix is from biogeneration – or provide fuel for heating and cooking. It is different from fossil gas (or ‘natural’ gas), which is extracted from rock via drilling or fracking.
What is biogas?
Biogas is generated from organic matter and contains around 60% methane and 40% carbon dioxide. It is made from a process called anaerobic digestion (AD), where microorganisms break down plant and animal products in a sealed, oxygen-free tank. Refining the biogas and removing the carbon dioxide creates biomethane, which can be pumped into the public gas grid and used in the same way as natural gas.
Biogas can also be burnt to generate heat to turn a turbine and generate electricity.
How does anaerobic digestion work?
Organic waste including plants, food waste and manure is fed into a sealed tank, where it can be broken down by bacteria in an environment with no oxygen. The bacteria produce methane amongst other gases, which gets pumped off as biogas.
Solid or liquid material left over from the process is called digestate. This can be used by farms as crop fertiliser, livestock bedding or as enrichment for soil due to the high nutrient content. In this way, anaerobic digestion becomes part of a circular renewable system, where the digestate is used to grow plants which can be used to make more biogas.
Wet versus dry anaerobic digestion
The material that is put into an anaerobic digestor for breaking down is known as feedstock. There are two types of feedstock, wet and dry.
Wet feedstock is classed as having less than 20% total solids and often contains waste from food manufacturers, restaurants and breweries. The digestion process is continuous, as the organic matter can keep being added to, meaning that more biogas can be produced.
Dry feedstock contains around 20-40% total solids and is good for breaking down substances such as waste crops, household waste and animal manure. This method produces biogas in phases, so several digesters are often needed to work together to produce a continuous supply of gas.
There are almost 600 operational AD plants across the UK. In 2020 the total amount of energy produced from anaerobic digestion was equivalent to the energy from over 1 million tonnes of oil.
Biogas and Good Energy
We aim to source biogas in as sustainable a way as possible, by buying from generators with high environmental standards. For example, we make sure that land used for growing energy crops does not interfere with natural biodiversity or habitats, and the crops themselves are not produced at the expense of any food supply.
Some of the key principles we follow when working with biogas producers include:
- The feedstock must be either renewable or from waste.
- Transportation of feedstock must be minimised to reduce emissions.
- Energy crop use must be minimised where reasonably practicable.
Small scale biogas
For the remaining 90% of the gas we supply to customers which is not from biogas, we offset the emissions by supporting Gold Standard projects around the world to generate biogas. These projects work with farming communities around the globe to build biogas digesters, providing people with clean, renewable energy. You can read more about our green gas here.