Carbon Considerations courtesy Soben Inc USA 2023
The race is on in the construction industry to support the global transition to net zero. Recent years have seen improvements in reducing operational carbon emissions, but a lack of clear benchmarks and reporting standards as so far hindered progress around embodied carbon. But what is embodied carbon? Soben’s Head of Sustainability, Dr Bonahis Oko, explains.
It’s no longer enough for companies to reduce their immediate carbon emissions, they must look up and down their value chains too. For those building new assets, that means considering embodied carbon. But when people say ‘embodied carbon’, they may not always be talking about the same thing.
What is embodied carbon?
Strictly speaking, embodied carbon is all the greenhouse gas emissions associated with a material or product, incorporating the extraction of the raw materials from the ground, the manufacturing and transportation of these products to sites, maintenance, repair and replacement in use to demolition and dismantling of a built asset, and sometimes beyond into reuse.
Embodied carbon can also describe impacts due to the earlier phases of a product’s life only; such as the emissions from ‘cradle to gate’, up to the point a product leaves a manufacturer’s facility. Construction clients may consider ‘cradle to use’, emissions up to the point of completion when an asset is handed over to its user or owner.
It is worth remembering that ‘carbon’ is shorthand for carbon dioxide equivalent (CO2-eq), that is all greenhouse gas emissions expressed in terms of the global warming potential (GWP) of carbon dioxide. Methane, for instance has a GWP of 25 which means that 1 million tonnes of methane is equivalent to 25 million tonnes of carbon dioxide.
Why the sudden surge of interest in embodied carbon?
In simple terms, we’ve made reasonable progress in reducing operational carbon; from decarbonising electricity supplies to improving energy efficiency of buildings. Now, we must tackle the more difficult task of reducing embodied carbon.
Clearly, the proportion of whole life carbon that comes from embodied carbon varies hugely between building types and between countries. For instance, embodied carbon will be a far smaller piece of the pie for data centres, with their huge cooling and equipment loads, than for a recently built office block. And in Norway, with its ample supply of hydro power, embodied carbon would account for a higher proportion of whole life carbon than in, say, the United States.
As governments and investors are demanding more rigour in carbon reporting, organisations are being forced to look beyond their Scope 1 emissions, which covers direct emissions due to its activities and their Scope 2 emissions, which covers indirect emissions from purchased energy for heating, cooling and electricity to their Scope 3 emissions which are indirect emissions from activities upstream and downstream. Embodied carbon falls into Scope 3 emissions.
National and corporate drives towards ‘net zero’ are reinforcing this. For organisations who are looking to achieve net zero whole life carbon for their built assets – as opposed to net zero carbon in operation – it makes sense to reduce the embodied carbon of a new asset as much as possible. Whether embodied carbon can be compensated for by deploying on-site renewables, or by offsetting carbon, paying more for lower embodied carbon products and solutions can make financial sense.
How do you calculate embodied carbon?
‘Calculating’ embodied carbon can be quite a broad-brush affair. Databases of generic cradle-to-gate embodied carbon values are generally used with carbon calculating software. Calculations can then be refined by plugging in more accurate data when specific products and suppliers have been selected. Some software also allows the impacts of transport to be taken into account too, although emissions from transport are typically very small compared to those from manufacture.
Information from manufacturers is likely to come from Environmental Product Declarations (EPDs), which is a standardised description of the environmental profile of a product. EPDs must be independently verified, with the life cycle analysis (LCA) report provided to the verifying organisation.
There are several standards which set out how LCAs should be carried out:
BS EN 15978:2011 Sustainability of construction works – assessment of environmental performance of buildings – calculation method
ISO 14044:2006 Environmental management — Life cycle assessment — Requirements and guidelines
RICS Whole Lifecycle Carbon Assessment Professional Statement (1st edition 2017)
Obviously EPDs can also include some element of assumption or generalisation too. For instance, the way electricity is generated may vary between manufacturing facilities.
If EPDs are being used as part of a product selection process, it is important that baselines, boundaries and calculation methods are agreed and consistent. Otherwise, comparisons can become meaningless.
Who is interested in embodied carbon?
There are an increasing number of built asset owners, in both the public and private sectors, who are asking for embodied carbon to be measured – and reduced – as part of the construction delivery process. Here, we are largely talking cradle-to-use embodied carbon. Perhaps the most advanced is Norway’s public roads administration Statens vegvesen which asks for a financial and carbon estimate at tender on contracts over a certain size. They then adjust the tender prices with the lowest bidder in carbon terms having nothing added onto their tender price but the other bidders’ prices increasing by 5 NOK (€0.5) for every kilogram of carbon their bid is above the lowest one.
Elsewhere, major contracts are asking for carbon savings to be made. For example, National Highways in the UK included carbon reduction targets in its tender for the £1.9m Lower Thames Crossing. Denmark is introducing embodied carbon targets into its building regulations, ramping them up between 2023 and 2029. And from 1 January 2023, the US Federal Government will consider embodied carbon when purchasing steel, concrete, asphalt and flat glass for its projects. Major corporations are moving in the same direction. In November 2021, MacDonalds opened its first ‘net zero carbon’ restaurant in the UK. With onsite power generation through PV panels and a wind turbine, and careful selection of building products, it calculated that the restaurant in Market Drayton has no carbon footprint. Commercial developer Landsecs in its net zero pathway has set reduction targets for embodied carbon intensities – kilograms of carbon per square metre – for new developments.
It is in response to this rise in demand for embodied carbon reduction, and the need to understand decisions alongside capital cost and construction impacts, that Soben launched its Carbon Cost Management service in November 2022.
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