Bioenergy refers to electricity and gas that is generated from organic matter, known as biomass. This can be anything from plants and timber to agricultural and food waste – and even sewage.
The term bioenergy also covers transport fuels produced from organic matter. But on this page, we’re just focusing on how it’s used to generate electricity and carbon neutral gas.
How does biomass generate energy?
When biomass is used as an energy source, it’s referred to as ‘feedstock’. Feedstocks can be grown specifically for their energy content (an energy crop), or they can be made up of waste products from industries such as agriculture, food processing or timber production.
Dry, combustible feedstocks such as wood pellets are burnt in boilers or furnaces. This in turn boils water and creates steam, which drives a turbine to generate electricity.
Wet feedstocks, like food waste for example, are put into sealed tanks where they rot and produce methane gas (also called biogas). The gas can be captured and burnt to generate electricity. Or it can be injected into the national gas grid and be used for cooking and heating.
Bioenergy is a very flexible energy source. It can be turned up and down quickly to meet demand, making it a great backup for weather-dependent renewable technologies such as wind and solar.
Is bioenergy environmentally friendly and sustainable?
Burning biomass does release carbon dioxide. But, because it releases the same amount of carbon that the organic matter used to produce it absorbed while it grew, it doesn’t break the carbon balance of the atmosphere.
In comparison, burning fossil fuels releases carbon dioxide that has been locked away for millions of years, from a time when the earth’s atmosphere was very different. This adds more carbon dioxide into our current atmosphere, breaking the carbon balance.
The overall sustainability and environmental benefits of bioenergy can depend on whether waste feedstocks or energy crops are being used.
Waste feedstocks & Energy crops
Waste biomass gives off gases naturally when it rots. If this happens in a place where there’s no oxygen, such as food waste buried deep within landfill, it can generate methane which is a much stronger greenhouse gas than carbon dioxide. Instead of allowing methane to vent into the atmosphere, breaking it down in a sealed tank allows it to be captured and burnt. Burning methane leaves you with carbon dioxide and water, which are better for the environment.
Energy crops are grown specifically for generating energy. So, unlike capturing methane from waste, there isn’t an argument that burning them reduces greenhouse gases which would have been given off anyway.
However, energy crops can still be low carbon if they are managed sustainably. For example, when energy crops are burnt, equivalent crops should be planted that will absorb the same amount of carbon that was released by burning.
Does Good Energy use bioenergy?
Yes. 20% of our renewable electricity is from biogeneration and 6% of the gas we supply is biomethane (this will be 10% from 1st April 2020).
Our biogeneration procurement policy makes sure that we only contract with bioenergy generators that have sustainable and responsible generation practices.
To keep our energy supply as clean and ethical as possible, we only source bioenergy that meets the following requirements:
- It must come from waste or sustainable sources
- Land must be used sustainably, respecting natural habitats and biodiversity
- Energy crops must not impact food production
- Animal welfare must be respected
- Transportation of biofuels should be minimised
- Biofuel generators should be highly efficient and able to put waste heat to good use
- Impacts on air quality must be appropriately managed
- Green Gas must be certified under the Green Gas Certification Scheme