By David Jenkins
Decarbonisation is one of the great challenges facing the construction industry, and to meet that challenge, infrastructure planners are increasingly focusing on the issue of embodied carbon.Â
According to a recent KPMG report, 22% of buildings’ carbon emissions come from embodied carbon, with operational emissions accounting for 78%.
There are several definitions of embodied carbon, but perhaps the clearest way to understand it is to measure the emissions from building materials, their construction, and potential demolition and disposal.
Typically, the focus has been on operational emissions, which is why, in so many cases, older buildings have been demolished and replaced by new ones with modern environmental features.
An understanding of embodied carbon, however, has led some planners to rethink and calculate that a better decarbonisation result can come from not releasing all of the embodied carbon contained in the building.
This is based on a calculation of the complete lifecycle of building materials, and the emissions released not only through demolition, but also from transporting those materials to a place where they can be disposed of, and the disposal process itself.
One example is in Sydney, where the property and construction company Stockland originally planned to demolish its head office and build a new one.
On further investigation, Stockland understood that while it could create a highly sustainable building as a greenfield project, a better outcome could come from retrofitting and working with the existing structure.
In 2021, Stockland received planning approval from the City of Sydney for a new $1.5 billion A-grade office tower of 36 storeys spanning 100,000 square metres of floor space.
The original plan was to demolish the existing building and start afresh, but a study tour of Europe to look at sustainability issues prompted a change of thinking.
On reflection, it was decided to keep the steel and concrete ‘bones’ of the existing 1990s building and create a new structure around it.
Demolition would release carbon already embedded in the concrete and steel, and this would need to be factored into the final carbon footprint.
Effectively upcycling the building this way was expected to save around 23,000 tonnes of embodied carbon.
According to the Green Building Council of Australia, embodied carbon comprised 16% of Australia’s built environment emissions in 2019.
If nothing is done to address this, and embodied carbon continues to be released, this could increase to as much as 85% by 2050.
New buildings also include a significant percentage of embodied carbon, and some jurisdictions are addressing this.
The Green Building Council estimates that if Australia reduced the embodied emissions in new commercial and residential buildings by 10% between now and 2050, this would eliminate at least 63.5 megatonnes of emissions – the equivalent of taking 13.8 million cars off the road for a year.
In New South Wales, the Sustainable Buildings Environmental Policy was issued in 2022.
Under this policy, the planning process for new buildings must quantify the embodied emissions attributable to the project. It must also plan to minimise construction waste and the use of fossil fuels on-site.
The National Australian Built Environment Rating System (NABERS) identified that measuring and managing embodied emissions in buildings needs to be tackled if Australia is to achieve its net-zero emissions target by 2050.
Reducing embodied carbon is closely tied to embracing the principles of the circular economy, which involves using materials for the longest period possible.
In a world that demands more construction and infrastructure, embodied carbon is a new challenge and will require new standards, policies and regulations.
The sooner it becomes a core part of our approach, the closer we will be to achieving net zero goals and making the construction industry more sustainable.
