Swansea City Bay Region Offsetting Study


City Science was commissioned to conduct an offsetting study by Carmarthenshire County Council on behalf of the partner authorities as part of the Economic Acceleration and Regeneration through Innovation (EARTh) program. We partnered with local authorities from the Swansea Bay City Region (Pembrokeshire Council, Carmarthenshire Council, Neath Port Talbot Council and Swansea Council) to create an offsetting strategy to sequestrate or reduce the three local authority’s residual emissions in order to meet the ambitious Welsh Government net zero target by 2030.

Client Brief

Each local authority expects to have some residual emissions in 2030. The local authorities in the Swansea Bay Region needed to understand their available options, in terms of carbon offsetting, what will be acceptable to Welsh Government, and give some indication on the cost to offset 1 tonne of CO2e. We provided co-ordinated regional support around understanding this carbon offsetting, in liaison with Welsh Government decarbonisation team, to help the local authority’s plan and budget for carbon offsetting in the future.

Our Response

City Science used the emissions figures that each local authority had most recently reported to the Welsh Government and created carbon reduction scenarios that had varying degrees of residual emissions. Using the modelled residual emission scenarios, we considered carbon offset options that the Welsh local authorities could implement. To understand the best offsets to implement; we carried out workshops with the local authorities and the Welsh Government to determine best practice, literature reviews of Welsh and UK policy on carbon offset policies, and modelling to determine carbon reduction/sequestration potential of various carbon offset practices. To fulfil the client’s brief we:

  • Assessed carbon reduction pathways and their potential residual emissions
  • Engaged with the Welsh Government to determine their offsetting requirements
  • Carried out detailed analysis of various offset methods
  • Created the multi criteria assessment tool to determine the best offset option
  • Developed an Offsetting Toolkit for the Welsh Local Authorities

Our Engagement

We facilitated workshops with the local authorities and the Welsh Government to determine the best practice for offsets for Welsh local authorities. We investigated the needs of each local authority, through discussion, based around formation of our offsetting toolkit. Once the toolkit was finalised we carried out a toolkit tutorial to clearly show how to use the tool and discuss its output.


We produced a detailed report with in-depth literature reviews and an offsetting toolkit for the Welsh local authorities to use at present or in future. It considers a multicriteria assessment (MCA) tool that carries out prioritisation of offset criteria to create a strategic output. Our toolkit allows for a high degree of flexibility of inputs as we understand that regulations, costs, and the councils’ land availability could be subject to change between now and 2030. The tool incorporates CO2 sequestration/ reduction of each offset, costs associated with the specific offsets and the land use changes to implement them. For each of these criteria the user can either use the 2023 predictions that we have provided, or the tool allows for their own flexible input to create the strategic output plan.

For more information, contact info@cityscience.com.