Positive figures in the sequestered (or biogenic) carbon

  • Hi,

    I am completing a WLC project in London and I have noticed that the sequestered carbon (or biogenic: GWP B) is positive for some of the templates, when it should be a negative figure. I guess it mostly in the templates where the concrete is added manually within eTool. Do you know why this happens? How can we correct this number?

    Please find below the images of the ‘All impact report’ showing this GWP B as a positive figure in some elements, i.e. for the substructure, and the templates used in this category.


    Hi Eliseo,

    The reason why there are positive figures under sequestered carbon for concrete is because the concrete industry burn a lot of waste tyres to generate energy for cement production. The burning of the tyres causes a release of biogenic carbon. This is an example where a regulator (in this case Greater London Area) has tried to reinvent parts of EN15978 without fully understanding the methodology behind the standard. So, no, not all sequestered/biogenic carbon impacts will be a negative figure by default because there are processes that releases biogenic carbon.

    We recommend that you send those results to GLA as is so that they may begin to realise their attempted simplification of complex supply chains is flawed.


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