You only need the hole open long enough to backfill it. “What Katharina found was that when you need a wind turbine, you’re making a hole in the ground (but) you’re not really draining what’s around. “So not only are you oxidizing the peat you removed, but you’re also drying out a massive area round it”. ![]() He stressed the “huge assumption everybody makes” was that it was necessary, in order to create a hole in the ground for a wind turbine, to remove all the peat, then put in the hard standing, and have drained all round, to a distance of perhaps 100 meters. However, “once you drain it, you expose it to the oxygen so the microbes then have oxygen available and the peat will be metabolized”, causing CO 2 to be released. When wet, peatbog contains no oxygen and very few microbes, “so the carbon in it is protected” from degradation. Her mentor, college lecturer Alasdair MacLeod, explained that peat was “90% water bioweight”. However, Lutz found that less drainage takes place than had been thought – and that extensive drainage is not necessary as the hole can be backfilled. When concrete foundations are being laid, peat is usually disposed of by being spread thinly over the surrounding area, with the assumption that all the displaced carbon will end up as atmospheric carbon dioxide. The calculation of CO 2 displacement associated with turbine electricity production uses the fossil fuel emission factor for the United Kingdom in 2016 rather than the overall grid emission factor in order to accurately reflect the generation type displaced by the wind turbine output.” ![]() “The result is based on a flora analysis and accurate peat depth and composition measurements, and references three years of electricity generation data. However, existing turbines on a wind farm on the Isle of Lewis, Scotland, on a site which is typical of the region, were found to have a carbon payback time is only 47 days when the actual impact following several years of operation is established. ![]() “The main reason for these projected high carbon payback times is the assumption that all displaced peat becomes fully oxidized and that the construction not only causes drainage within the immediate construction area, but that the effect can extend outwards by a distance of up to 400 m. The report further summarized: “Installing large wind turbines on peatland has the disadvantage of exposing carbon long trapped in the ground to decomposition, and some estimates suggest a turbine can take several years of operation to compensate for the associated carbon dioxide emissions. This is based to an extent on an influential report by Nayak and collaborators at the University of Aberdeen who developed a carbon dioxide calculator, variations of which are still used to estimate the impact of a wind farm proposal (both by supporters and opponents)”. Lutz carried out her research at Beinn Ghrideag near Stornoway in the Autumn, with the academic support of mentor Alasdair MacLeod from Lews Castle College UHI and financial support from community wind farm owner Point and Sandwick Trust.Īccording to her report, entitled “CO₂ Emissions from Wind Turbines on Peatland: A Practical Calculation”: “Estimates for the payback time for turbines on peatland have been quoted as 2.3 years (Pearce, 2009). When peat is disturbed for large concrete foundations to be laid for turbines, greenhouse gases are released into the atmosphere. ![]() ‘Carbon payback’ is a term referring to the length of time it takes for the negative environmental impact from the construction of a wind farm on peatland to be offset by the positive environmental impact of generating clean energy instead of burning fossil fuel. University research finds this wind farm had a carbon payback time of just 47 days – a drastic reduction on the previous estimate of 2.3 years. (Photo: Sandie Maciver of SandiePhotos) Point and Sandwick Trust’s community-owned wind farm at Beinn Ghrideag.
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