Carbon footprinting: the proof is in the pipeline

Measuring a carbon footprint is a complex business, says Stuart Crisp of the Concrete Pipeline Systems Association (CPSA), especially when it comes to pipes

There is widespread ambiguity and misunderstanding about what a carbon footprint actually is. A carbon footprint is a measure of the impact of climate change and is expressed as carbon dioxide equivalent (CO2e), not just a measure of CO2.

In a true carbon footprint, all greenhouse gases (GHG) are measured. All GHGs that are not carbon dioxide are measured based on their comparative effect on climate change to that of CO2. For example, methane is currently regarded by IPCC as 25 times more damaging to the environment than CO2 and therefore 1kg of methane would be reported as 25kg CO2e.

Many industry measures of carbon footprint report CO2 only and although CO2 can make up over 90% of the GHG emissions, there are notable exceptions. For example, plastics manufacture is recognised as emitting large amounts of methane and so the CO2 only measurement may under report the true impact of that manufacturing process.

Let us take a closer look at concrete pipes. As the trade association for this sector, the CPSA decided it was down to them to give a definite measurement for the CO2e emissions in concrete pipes and associated concrete products.

In order to establish the true carbon footprint for their products, the CPSA has recently put together a Partial Life Cycle Assessment report of the carbon emissions from precast concrete pipes, manhole rings and cover slabs. CPSA carried out an audit with four major concrete pipe factories in the UK which between them produce over 70% of concrete pipeline products in the UK.

This cradle-to-gate assessment, completed in compliance with PAS 2050, looked at the GHG emissions of all consecutive and interlinked processes from the extraction of the raw materials to the site delivery stage.

Having looked rigorously at all areas of the production and transportation processes, the CPSA's results conclude that concrete pipes have a CO2e per metre ranging from 17.77kg CO2e per metre for 225mm diameter pipes up to 592.07kg CO2e per metre for 2,100mm diameter pipes. These measurements are significantly lower than calculations for generic precast concrete based on many CO2-only carbon calculators and industry databases, which can over-report the carbon footprint by around 20%.

In contrast, some plastic pipe studies have under-reported the true level of embodied carbon emissions, because they have not included the emissions of all GHGs.

Emissions of methane during the manufacture of plastic pipes can increase the true carbon footprint by around 25% and the country of origin of the resin can also lead to significant variations in the total.

On top of this, the different structural behaviour of pipes made of different materials means that the way in which pipes are installed can also vary, leading to important variations in the emissions for alternative bedding designs.

Rigid pipes, such as concrete, are structural elements and the integrity of a pipeline is derived mainly from the pipe itself. In contrast, flexible pipes (for example, plastic), behave very differently and are mostly reliant on the design and quality of the installation to ensure structural soundness. This can often result in less granular material being required for the installation of an equivalent size of concrete pipe compared to plastic.

The CPSA audit includes a cradle-to-site embodied carbon comparison for concrete and plastic pipes. The report clearly demonstrates that concrete pipes have up to 27% lower embodied carbon compared to plastic, even more when alternative bedding designs are used.

All firms should re-assess their carbon footprint measurements and those stated by their suppliers - it is not always enough to measure carbon as a single gas, all GHGs must be recorded in order to provide a true measurement of a product's impact. But carbon footprinting is not the only way for firms to demonstrate their environmental credentials.

A true CO2e measurement should work alongside measures to improve at least some of the other recognised environmental impacts such as embodied energy, waste, water footprinting, responsible sourcing of raw materials, end of life reuse and recyclability. And of course once you have got the true carbon footprint, the next job is to work out how to reduce it further.

Rigorous control and measurement of all processes involved in manufacture must be continuously assessed and improved so that GHG emissions do not creep up or remain stagnant, but are actually cut. The only way the Government's tough targets are going to be met is if intelligent environmental controls are built into every area of industrial life. Getting a true measure of GHG emissions is a great place to start.

The CPSA has just undertaken a major study in to the embodied carbon of its members products and will be publishing the findings of this research shortly.

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