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Concrete In Australia : March 2013
48 Concrete in Australia Vol 39 No 1 FEATURE: ANCHORING & PRECAST included at Bath University s Inventory of Carbon & Energy was calculated by researchers at the university from a number of sources. e value is completely based on secondary information and would include a range of assumptions associated with factory waste generation or production methods which the authors could not justify. e value for greenhouse gas emissions at precast factories used by the database also seems considerably higher than the average greenhouse gas emission levels for members of the British Precast Concrete Federation for 2007, 2008 and 2009. • ere is no information, either in the original report or published paper, that the study carried out by Specht & Lorenz (2010) was based on a recognised carbon footprinting/LCA standard. e paper also refers consistently to carbon dioxide emissions (and not greenhouse gas emissions) and appears to have a relatively high cut-off criterion (≥ 2%). However, the same combination of secondary upstream and primary downstream data was used and the proportions of emissions associated with different factors are similar to the other two studies. It is understood that a combination of old and primary data (from 1995 and 2006) was used. Data was collected from a wide range of sources in Germany and secondary information was used for upstream data (including the cement carbon footprint). e relatively low carbon dioxide emissions associated with the precast concrete factory operations (around 10.6 kg CO2/t) shows that the level of accelerated curing (usually with the use of steam) is limited in the factories considered in the study. e considerable difference in the final carbon footprint value between the three studies reflects how a combination of concrete specification, data sourcing and calculation methodology can affect the carbon footprint of a precast product. e difference in values also proves the difficulty of resorting to a "generic precast concrete carbon footprint" and the caveats associated with the use of secondary information. e fact that the proportions of emissions sources may seem similar in these three studies (and many other studies) does not necessarily mean that this would be the case for every single precast concrete product. e examples above also show how some of the least polluting precast concrete product sectors can be penalised by the "generalisation" of concrete carbon footprinting values and criteria. 3.0 CASE STUDY: THE CARBON FOOTPRINT OF CONCRETE PIPELINE SYSTEMS e aim of this case study is to demonstrate how a combination of the factors and caveats demonstrated at Section 2 can lead to incorrect findings and conclusions in regards to the carbon footprint of concrete: Concrete Pipeline Systems Association (CPSA) conducted a study in 2010 and 2011 to calculate the carbon footprint of three of its products (concrete pipers, concrete manholes and cover slabs). e study was expanded to address a number of other objectives. 3.1 Goal and scope In addition to the calculation of the carbon footprints of concrete pipeline products, CPSA wanted to see how these footprints compare to equivalent plastic pipeline systems. e study was also aimed at looking at a number of reports and claims made in the media about how concrete pipes compare to plastic equivalents. Most these claims were based on calculations built using Version 1.6 of the Bath University ICE database. at version of the database included values for the carbon footprint of "prefabricated concrete" and PVC and HDPE pipes of 215, 2500 and 2000 kg CO2/t respectively. Unverified comparative assertions were made by different parties based on calculations built on these values: Most notably, a comparison between concrete and plastic based underground water storage and attenuation systems was used at an Environment Agency report, entitled "Evidence: Energy and carbon implications of rainwater harvesting and greywater recycling", where the calculations were based on the carbon footprinting values above. Due to the many unanswered questions with the current ISO standards used for carbon footprinting, as detailed by Finkbeiner (2009), it was decided to use PAS2050 (2008) as the main specification for the carbon footprints of the concrete pipeline products. e functional unit for the concrete/plastic pipe comparison was designed carefully to include the function of transporting sewage, which required the consideration of a pipe length (1 linear metre) of installed pipeline (including the bedding surround). 3.2 Life Cycle Inventory and Impact Assessment CPSA compiled a Life Cycle Inventory for concrete pipes, manholes and cover slabs product systems from four UK pipe factories representing 72.4% of the total tonnage production in 2009 for pipes and manhole rings. Input and output Table 2. Cradle-to-gate carbon footprints of 1 m length of multiple concrete pipe and manhole sizes calculated by CPSA. Carbon Clear compared to footprints developed using ICE v1.6 database average emission values. Pipe size CPSA/ Carbon Clear footprints ICE (v1.6) based footprint Manhole size CPSA/ Carbon Clear footprints ICE (v1.6) based footprint DN300 25.6 37.5 --- --- --- DN600 72 105.3 --- --- --- DN1200 223.8 301.1 DN1200 129.24 189.6 DN1500 341.4 455 DN1500 187.15 275.3 DN2100 559 762 DN2100 314 456.9