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Firing up the sustainability agenda again

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  1. We must use a common metric for carbon because if we can’t measure and monitor it how can we prove that we are reducing carbon use.

    The carbon issue is complex, but in simple terms we have Greenhouse Gas Emissions (GHG’s) from the use of fossil fuels (coal gas and oil) these GHG’s include nitrous oxide, methane, HFC’s, carbon dioxide etc and an accepted measure is carbon dioxide equivalent CO2e . This, I would argue, should be our common carbon metric in the construction industry, not carbon and not carbon dioxide. Significant and extensive work has been done on the conversion factors of various materials. For example, currently the conversion factor for 1 kWh of mains electricity is 0.59 kg CO2e (these can change every year), 1kWh of mains gas is 0.18 kg CO2e.

    We can determine what a tonne of carbon looks like by using the excellent Environment Agency spreadsheet for the calculation of carbon on a construction site. They use a conversion factor for bricks of 0.24 tCO2e per tonne of bricks, and the bricks have a density of 1.9t per cu m.
    Therefore tonnes of bricks in one tonne of CO2e = 1/0.24 = 4.1667 t
    Cu m bricks in 4.1667 t = 4.1667 / 1.9 = 2.193 cu m
    Number of bricks in 2.193 cu m = 2.198/ 0.215 x 0.065 x 0.1025 = 1531

    Using the environment agency spreadsheet if the 1531 bricks travelled 100km from the factory gates to site by road this would add 44 kilograms of CO2e to the calculation.

    Therefore, in answer to the question what is a tonne of carbon, it is in the order of
    • 1531 bricks having a density of 1.9t per cu m or
    • 1700 kwh of mains electricity or
    • 5 cu m of mid range ready mix concrete or
    • 3.23 cu m of general timber

    Everything that we use on construction site can now be converted into CO2e the poster attached was displayed in the site offices to inform that carbon can be measured and to obtain a feel for the units. Please note the conversion factors used at that time is different because any replacement of future electricity hopefully will have less carbon content.

    Mistakes will be made calculating carbon and objections will be raised to the conversion factors of certain materials but as soon as we start using the Environment Agency spreadsheet or similar then rational discussions / debates / arguments can begin and carbon measurement can develop.

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