The built environment is in a prime position to address the emergency of climate change through the reduction of embodied carbon emissions from our buildings and infrastructure assets. According to the World Green Building Council, decarbonisation of the built environment is one of the most cost effective ways to mitigate climate change. With the global building stock expected to double in order to accommodate the world’s projected population of 10 billion, this growth will contribute to an expected doubling of the global consumption of raw materials by around the middle of the century, significantly increasing the building and construction sector’s emissions and climate impact.
The built environment is responsible for 40 percent of global carbon emissions, with embodied carbon emissions being especially critical. The carbon dioxide equivalent of emissions associated with the full supply chain of all materials and systems put into any built environment project, embodied carbon is different from operational carbon in that the latter can be improved over the lifetime of a building. If embodied carbon emissions are not addressed before the building project moves past the design stage, there is no way for building owners to reclaim lost carbon savings once the building is constructed and subsequently used.
Bringing Embodied Carbon Upfront
The breakdown of carbon emissions for buildings is typically 30 percent embodied carbon emissions versus 70 percent for carbon emissions due to building operations. In Singapore, where the lifespans of buildings tend to be shorter due to urban renewal, the embodied carbon emissions of buildings can constitute up to 40 percent of the total carbon emissions over the lifespan of the building.
The upfront emissions from materials and products used to construct buildings and infrastructure, and those installed later during maintenance and renovation, usually represent a significantly greater source of embodied carbon than all other stages in the lifecycle. Globally, cement and steel are two of the most important sources of material-related emissions in construction. Cement manufacture is responsible for around 7 percent of global carbon emissions, with steel also contributing 7-9 percent of the global total, of which around half can be attributed to buildings and construction.
Reducing Embodied Carbon through Prevention Framework
The WorldGBC has outlined a 4-step framework to reduce embodied carbon emissions through prevention, which is the best way to reduce embodied carbon. These principles can be applied by all stakeholders, regardless of their position in the value chain, the nature of their project or product, and the region they operate in.
Consider embodied carbon emissions and reduction strategies from the outset, whether for a whole project or for a single product. Question the need to use materials at all, considering alternative strategies for delivering the desired function, such as increasing utilisation of existing assets through renovation or reuse.
2. Reduce & Optimise
Use low carbon design guidance and calculation tools and benchmarks to evaluate each design choice in terms of upfront emission reductions and as part of a whole life approach.
- Apply design approaches that minimise the quantity of new material required to deliver the desired function.
- Prioritise materials which are low or zero carbon, responsibly sourced, and which have low lifecycle impact in other areas, including the health of the occupant, as determined through a product specific environmental product declaration where available
- Choose low or zero carbon construction techniques having maximum efficiency and minimum waste on site.
Consider future use scenarios and end of life, maximising the potential for maintenance, repair and renovation, and ensure flexibility for future adaptation. Design for disassembly and deconstruction to facilitate future reuse, selecting materials which can be recycled and which can be extracted and separated easily for processing.
As a last resort, offset residual embodied carbon emissions either within the project or organisational boundary or through verified offset schemes.