Water & Wastewater Treatment

WWT February 2017

Water & Wastewater Treatment Magazine

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Page 26 of 43

www.wwtonline.co.uk | WWT | FEBRUARY 2017 | 27 Stuart CriSp BUsinEss DEvElopmEnT DiREcToR concRETE pipElinEs sYsTEms AssociATion totting up the Carbon Working out the carbon footprint of a project such as a drainage installation involves a number of variables, with material choice playing a key part In the know Getting to grips with... carbon footprinting The carbon footprint of a project such as a drainage installation is measured in co2 equivalent A carbon footprint measures the total greenhouse gas emissions caused directly and indirectly by all activities within a defined set of boundaries. For drainage installations, emissions may cover the whole life of a drainage system, from the extraction of raw materials used in pipe manufacture to materials used to bed the pipe in the ground all the way through to what happens at the end of the pipeline's life as a drain or sewer. What gases contribute to an installation's carbon footprint? All six of the Kyoto Protocol greenhouse gases should be measured in an installation's carbon footprint: Carbon dioxide (CO2), Methane (CH4), Nitrous oxide (N2O), Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs) and Sulphur hexafluoride (SF6). A carbon footprint is usually measured in tonnes of carbon dioxide equivalent (tCO2e). The carbon dioxide equivalent (CO2e) allows the different greenhouse gases to be compared on a like-for-like basis relative to one unit of CO2. CO2e is calculated by multiplying the emissions of each of the six greenhouse gases by its 100- year global warming potential (GWP). Users should be aware that when comparing pipeline material options, some carbon footprint databases are based on CO2 emissions alone, which can cause confusion and lead to inaccurate assessments. When British Precast compared the CO2-equivalent figure for concrete to the CO2-only figure, it showed a minimal increase in emissions of 2% for concrete pipes. For plastic pipes, however, the increase in emissions is at least 20%, if the CO2-equivalent figure is used instead of the CO2 only figure. The main reason for this is that the manufacture of plastics usually creates significant emissions of methane, which has an impact 25 times greater than carbon dioxide, according to IPCC 2007 data. The difference could be even more pronounced if the resin used in the plastics manufacturing process is sourced from further afield - such as Asia - due to higher transport emissions and more carbon-intensive grid electricity. What should be included in the carbon footprint of a wastewater pipeline installation? In the case of wastewater pipeline systems both the material of pipes and bedding material used for their installation need to be considered. How useful are generic values in determining the carbon footprint of a drainage installation? The problem with generic carbon footprints and drainage installations is that when the generic figures are adjusted to reflect the values of specific applications there can be a huge deviation from the standard value. In fact, the deviation from

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