Energy from grass cuttings
We are trialling a new way to use grass cuttings to generate energy and reduce the council’s carbon footprint.
The trial is part of a £4 million project which is funded by the Department of Transport.
In partnership with West Sussex Council, the Greenprint project is investigating ways in which cuttings could be used to make biogas, biomethane fuel for vehicles, and an additive for asphalt road surfacing material called biochar.
Greenprint is part of ADEPT Live Labs 2, a 3 year, UK-wide £30 million programme funded by the Department for Transport and developed by the Association of Directors of Environment, Economy, Planning and Transport (ADEPT) that aims to decarbonise the local highway network.
What we are doing
We are using new machinery to cut and collect grass from selected green spaces and highway verges we manage, where we would normally leave the cuttings on the ground.
The number of cuts will also be reduced from typically 8 to 10 times a year to 4 to 5 times.
The grass cuttings are sent to an energy-from-waste plant in Cannington in Somerset where they are converted into biogas using a process called anaerobic digestion (AD).
An alternative way to produce biogas is to mix grass cuttings with household food waste, which is currently processed at the GENeco AD facility in Avonmouth. This process is pending Ofgem approval.
How it helps
Existing arrangements of mowing grass frequently and leaving the short cuttings to lay on the grass can help to return nutrients to the soil.
However this does not encourage other plant species to grow, which would create a more diverse natural environment and a home for more insects and other small creatures.
Leaving green areas to grow longer and removing material after cutting should:
- enable wildflowers, insects and other creatures to thrive
- allow the soil to store more carbon
Innovative use of the cuttings and mowing less frequently will help reduce our carbon footprint and work towards limiting the impacts of a changing climate.
Achievements so far
Some key achievements include:
- cutting and collecting grass from 85 hectares of land, which is equivalent to 140 football pitches
- establishing soil carbon sampling to analyse changes to the amount of carbon stored in the ground
- recording data from cut-and-collect and cut-and-leave approaches to grass cutting to assess the carbon impact of both
- beginning research into the impact the project has on biodiversity at selected sites
- developing a ‘how-to’ guide to share knowledge with other local authorities
Read the first year summary report.
Timescale
The project began in Yate in 2023.
It was extended in spring 2024 into the following areas:
- Bradley Stoke
- Kingswood
- Patchway
- Staple Hill and Mangotsfield
- Stoke Gifford
- Thornbury
The plots of grass included have been agreed following consultation with the parish and town councils.
The project duration is 3 years followed by a further 5 years of monitoring the environmental benefits, impact, and costs.
This information as well as feedback from the community will be used to decide whether we adopt the approach permanently. No date has been set for this decision.
If you would like further information or to share your feedback on the trial, email climate.emergency@southglos.gov.uk or call 01454 868000.
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