Infrastructure in 2014: Material gains for the planet
The construction industry has been set some tough carbon reduction targets, but is the issue being over-simplified?
The government’s Construction 2025 strategy document published earlier this year is providing the industry with a useful blueprint setting out “how industry and government will work together to put Britain at the forefront of global construction over the coming years”. One of the themes in the document is “low carbon and sustainable construction”, which is presented as both a challenge and an opportunity.
The report states that the transition to a low carbon economy presents the industry with “terrific” opportunities for growth, suggesting it is an area in which the UK could become a world leader. At the same time, though, the construction industry is expected to make a significant contribution to the UK achieving its stated aim of reducing CO2 emissions by 80% by 2050 compared with 1990 levels. This is not surprising, given that over half the nation’s greenhouse gas emissions come from the built environment.
The report identifies that, in infrastructure, the area over which the construction industry has the most influence is what it calls the “capital carbon” impact of what it produces. This term encompasses the energy used and carbon produced during the production of building materials - also known as the embodied (or embedded) carbon.
“A few years ago we had around a dozen requests a year for the carbon footprint of products; last year we had over 1,000”
Martyn Kenny, Lafarge Tarmac
It is something the industry has been getting to grips with over the last few years, with many organisations now routinely asking for information on embedded carbon in tender documents, according to Lafarge Tarmac sustainability director Martyn Kenny. “A few years ago we had around a dozen requests a year for the carbon footprint of products; last year we had over 1,000,” he says. “Increasingly we’re being asked for that information in tenders, and carbon reduction targets are being put into term contracts.”
He says the increase is partly a result of the Green Construction Board’s carbon reduction road map, which fed into the Construction 2025 report, and partly to meet individual companies’ own sustainability agendas.
However, while Kenny applauds the aims of Construction 2025, he is concerned that the focus on “capital” carbon is over simplistic, and the industry should instead be trying to better understand the carbon associated with the entire lifecycle of its products.
“Construction 2025 is a really good document in terms of giving vision and direction, and it struck a good balance,” he says. “But within it was the term “capital carbon”, and my concern is that people interpret capital carbon as just the carbon emitted in production up to the point of delivery.
“It is misleading to underestimate the carbon associated with the product in the context of a project, so focusing simply on the embedded carbon could lead to the wrong behaviours or to people making the wrong decisions,” he adds.
Kenny explains that a product that has “higher” carbon at the point of delivery could be three or four times more durable than the “lower” carbon alternative, or need less maintenance, and therefore have a lower carbon footprint over the lifetime of the asset in which it is used. “It is really important to focus on the whole life, from the extraction of raw materials, through manufacture, use in the construction process, performance of the infrastructure during its life, and recyclability at the end of its life,” he says.
Kenny acknowledges that it is “easier to measure embedded carbon rather than anticipate how it’s going to be used”, but is concerned that this over-simplification of the carbon issue may result in choices being made that have long term impacts.
“Producing a carbon footprint for a product at the point of delivery is a relatively straightforward process - usually focused around energy and chemical processes,” he says. “It’s a number you can come up with for people to latch onto relatively easily, whereas in-use carbon is more difficult to measure, because you are predicting the operational life of the material.”
He says it is up to material providers to come up with information that is as clear and transparent as possible in order for clients and contractors to make informed comparisons. But this involves materials firms getting involved in the design process at an earlier stage, rather than simply responding to requests for products with the lowest embedded carbon.
“In looking at the whole life, the materials supplier should get involved in the early days of the design of the project - then you can have a discussion about the carbon performance of the project as a whole,” says Kenny, who believes this might lead to consideration of products or materials that will help lower carbon emissions during the performance phase - such as using concrete for thermal mass in a building.
“This is not about choosing one material over another,” he adds. “It’s about looking at the overall project, and that allows you to make more informed choices.”
Kenny’s other concern is that, by putting so much emphasis on capital carbon in the choice of materials and products, specifiers might be ignoring other important sustainability impacts like responsible sourcing, transport, waste production and water use during manufacture, and the amount of recycled material in the product.
“Carbon is a very important thing,” says Kenny. “We have the threat of damaging impacts of climate change, so without doubt it is an important thing. But it is not the only important thing. It is important to look at sustainability as a whole.”
“We know carbon is a big issue, and it’s going to be a big issue”
Martyn Kenny, Lafarge Tarmac
Moves are already afoot by industry bodies to tackle some of these issues. In the roads sectors, for example, key players, including the Mineral Products Association (MPA), the Highways Agency and specialist consultant TRL, have developed the Asphalt Pavement Embodied Carbon Tool (Aspect), a standardised approach for calculating the life cycle greenhouse gas emissions of asphalt used in highways.
The concrete industry is also making huge strides in reducing both embedded and lifecycle carbon, and is helping suppliers produce accurate and meaningful Environmental Product Declarations that cover a broad range of sustainability issues.
The MPA’s cement group has produced its own 2050 road map for sustainability, which includes reducing CO2 by 81%. It has already achieved a 55% reduction on 1990 levels, much of this by using less energy-intensive production methods. The industry’s use of recycled materials in production is also helping to lower embedded CO2 levels, but Kenny says concrete is a good example of why whole life carbon should be considered at the specification stage. “At the end of the life of the asset, when concrete is crushed for recycling, it ‘recarbonates’, chemically binding CO2 from the atmosphere,” he explains. “The amount is equivalent to about 20% of the embodied carbon of the concrete at point of delivery.
“If material selection was based solely on the solution with the lowest installed embodied carbon, recarbonation would not be taken into account, whereas it can be if the carbon footprint over the whole life of the asset is considered.
“We know carbon is a big issue, and it’s going to be a big issue for a long time, so we’ve all got to understand our impacts and take action,” he concludes.
Resurfacing key London streets
Oxford Street, Regent Street and Oxford Circus in central London have very high volumes of slow moving traffic, making the road surface prone to rutting.
Historically the roads have been surfaced with conventional materials, but required regular patching and resurfacing every three to four months, with resulting disruption to traffic.
Westminster City Council was offered an alternative solution based on Lafarge Tarmac’s Masterlayer, which has 33% higher installed embodied carbon than the conventional solution. However, it has now been in place for six years without any patching, and is still in good condition.
Because it has not needed maintenance or replacement, the carbon footprint of the solution is 90% lower than the conventional solution over the life of the asset to date. If material selection had been based solely on the solution with the lowest installed embodied carbon, it would have resulted in a much high carbon emission over the whole life of the asset.