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As the construction industry embraces whole-life models for carbon consumption in projects and products, a forthcoming BPDA study should demonstrate a huge benefit in concrete pipe selection, says Matthew Butcher, sustainability & product association executive, British Precast.

The UK government’s push for net zero carbon by 2050 will see the developers of infrastructure projects paying much closer attention to the carbon impact of their choices of materials. The BPDA’s membership is committed to not only lowering the carbon impact of its product, but also assisting decision-makers by comparing the whole life carbon impact of concrete pipes with their plastic equivalent.

The climate emergency has come to the forefront of international public consciousness through a mixture of alarming scientific reports and public protests such as the School Strike for Climate and Extinction Rebellion. In 2018, the Intergovernmental Panel on Climate Change (IPCC) issued the most extensive warning yet on the risks of rising global temperatures – widely dubbed ‘the final call’. [1]

Industry must go above and beyond to answer this call from the climate scientists and the civil engineering sector is one of many within the built environment to formally declare its intention to tackle the climate emergency. Civil engineering practices in the UK are being asked to commit to a range of pledges linked to low carbon sustainable construction.

Set out by the Institution of Civil Engineers (ICE) these include an accelerated shift to low embodied carbon materials in all works as well as design principles that enable the UK to become a net-zero carbon economy by 2050. Critically the declaration includes a focus on wholelife carbon assessment, including recognition of the important role extending the life of infrastructure will play in carbon reduction. [2]

Two pledges in particular send a strong message to the civils sector to ensure that carbon assessments of products and projects are robust and verifiable. These are:

  • To include, as part of the basic scope of all our work, lifecycle costing, whole-life carbon modelling and post-construction evaluation in order to optimise and reduce embodied, operational and user carbon and other resources
  • To evaluate all new projects against the need to contribute positively to society and enhanced wellbeing, while simultaneously averting climate breakdown and encourage our clients to adopt this holistic approach using PAS2080 to reinforce sound decision-making.

The approach set out in the PAS2080:2016 standard for Carbon Management in Infrastructure seeks to identify the total carbon, that is the sum of carbon consumed across all the lifecycle stages of an asset. This is to avoid making a carbon reduction in one lifecycle stage which leads to an increase in carbon in a later lifecycle stage and therefore to a net increase in whole-life carbon.

The example given by guidance from both the Royal Institution of Chartered Surveyors (RICS) and the Royal Institute of British Architects (RIBA) is that specifiers should make sure that using low carbon materials to reduce capital carbon during installation does not lead to more carbon from material replacements during the operational stage. [3]

The BPDA is already actively engaged in producing resources to facilitate decision-making around whole-life carbon and will, in due course, publish a study comparing the cradle-to-grave global warming potential of concrete and plastic drainage systems.

A whole-life carbon focus is important because some plastic pipe studies may have under-reported the true level of embodied carbon emissions in their assessments by not taking account of multiple greenhouse gases or not including all lifecycle stages.

On a limited lifecycle stage assessment of drainage systems it is possible to omit important impacts further into the asset’s lifespan or linked to the product’s installation. Much like the famous Indian parable where six blind men describe an elephant from touching one feature of the animal, studies that look solely at cradle-to-gate carbon emissions or at single emission sources like transportation can miss the big picture.

The BPDA study was guided by the European standards EN 15978 Environmental Impact Assessment of Buildings and EN 15804 Environmental Product Declarations (EPD). This is important because PAS2080:2016 notes that data consistent with the modular lifecycle assessment (LCA) approach and principles set out in EN 15978 and EN 15804 should be used in a comparison like the one the BPDA is undertaking.

It should be noted that the comparisons carried out by BPDA are not entirely compliant with the standards described because of a lack of verifiably compliant plastic pipe data. The data for the concrete pipes used in this study is however based on the externally verified EN 15804 EPD and calculator. BPDA would be prepared to produce a full set of compliant data if the plastic industry were to do so.

In 2017, the BPDA published an EPD for 1m of DN600 precast concrete pipe with class B bedding. This was an Association declaration using primary data from member companies, covering all lifecycle stages from A1 to C4.

Once published, the BPDA’s new carbon report is set to show that at the majority of pipe diameters, and with plastic pipe ring stiffnesses and resin sources evaluated, installed concrete pipes have a lower carbon impact.

For large diameter pipes the difference is the most marked, with the carbon impact of 4kN/m2 DN2100 plastic pipes as much as 55% higher than that of a concrete equivalent. When the full lifecycle in taken into consideration the BPDA believe that the carbon impact of a plastic pipeline could be more than double the carbon impact of a concrete pipe. This is primarily due to the longer service life of concrete pipes.

Concrete’s extended service life, which is more than double that of plastic pipes in many cases, removes the need for replacements within the assets design life. Its durability also extends past the design life, reducing risks associated with current projected 800-year service life requirements of UK water assets. [4]

Selecting concrete pipes also reduces bedding requirements, which in turn lowers the amount of imported granular bedding material required for installation. This not only reduces the carbon impact of transporting and quarrying the bedding material, but also increases the material efficiency of the development. The use of plastic has the opposite effect as oil-based products are non-renewable.

Conducting an LCA study of this type not only aids in product comparisons but also allows the sector to perform hotspot analysis. This analysis allows the industry to focus sustainability efforts and bring down the lifecycle carbon of our products.

The ultimate goal being the design and installation of net zero carbon pipelines.

Use of Portland cement replacement products is one area where the UK concrete is already ahead of global trends. Recent media reports suggest that global cement production is responsible for 7-8% of global CO2 emissions, in the UK this is only 1.5% of UK emissions.

The Concrete Centre’s This is Concrete – Ten Years, Ten Insights (2018) publication highlighted that countless innovations have achieved a 28% reduction in the embodied carbon of concrete since 1990. The precast concrete sector specifically has reduced CO2 emissions per tonne by 12.1% since 2012 and is on course to meet its 2020 targets for carbon reduction.

[1] IPPC. Special Report. Global Warming of 1.5°C. www.ipcc.ch/sr15/
[2] ICE. UK Civil Engineers Declare Climate & Biodiversity Emergency www.civilengineersdeclare.com
[3] RICS. Whole life carbon assessment for the built environment, 2017
[4] Department for Environment, Food & Rural Affairs, Water for life: white paper, 2011

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