Australia has significant potential to reduce its carbon footprint on major building and infrastructure projects, a new report has found.
Developed by Edge Environment for the Clean Energy Finance Corporation, the Australian buildings and infrastructure: Opportunities for cutting embodied carbon report has identified and quantified opportunities to reduce the carbon footprint of construction and outlines material and design initiatives which can reduce embodied carbon in new projects on a cost effective basis.
It found that substantial reductions in embodied carbon are already being achieved.
In its report, Edge analysed 69 building projects which have received Green Star ratings from the Green Building Council of Australia along with 20 road, rail, port and water projects which had been awarded Infrastructure Sustainability As-Built ratings by the Infrastructure Sustainability Council of Australia.
Compared with equivalent designs without sustainability measures, it found that the building projects analysed delivered average reductions in embodied carbon of 15 percent.
Meanwhile, the infrastructure projects studied delivered an average 33 percent embodied carbon reduction.
Moreover, the report found that solutions are available which can help to minimise the cost associated with reducing embodied carbon.
Indeed, depending on the initiatives which are implemented, embodied carbon reductions of five to eighteen percent are achievable whilst also delivering material costs reductions of between 0.4 percent and 3.0 percent.
As with operational carbon, the need to reduce embodied carbon in buildings and infrastructure has become increasingly important amid growing concerns about climate change.
Unlike emissions which occur in operations, embodied carbon emissions occur within a building’s construction through resource extraction, manufacturing and transport of materials.
As things stand, Edge estimates that the embodied carbon emissions of materials used in building and infrastructure amount to between 30 to 50 million tonnes of carbon dioxide equivalent and account for between five and ten percent of natural greenhouse gas emissions.
In its report, Edge said opportunities to reduce embodied emissions are concentrated in early project stages (see chart).
These include measures to avoid or minimise the need to build new assets by better using, renovating or reusing existing assets through to use of low carbon materials and optimisation of material use through efficient design.
On building projects, it found that practical strategies include replacing conventional reinforced concrete with other structural materials such as timber.
Another strategy involved replacing traditional concrete mixes containing Portland cement with those containing waste materials such as fly-ash.
One example on which both techniques were employed is the nine-storey 25 King building (pictured above) delivered by Lend Lease in 2018 as part of the $2.8 billion renewal of Brisbane Showgrounds in Bowen Hills.
Known as Australia’s tallest commercial timber building, this was constructed using glue laminated timber (Gluelam) columns and beams along with cross laminated timber floors.
Where concrete was needed for remaining portions of the design, mixers using waste materials were used in place of Portland cement.
Compared with traditional reinforced concrete, the building delivered reductions of 38.7 percent in embodied carbon emissions and 74 percent reduction in overall carbon emissions over a 60-year life.
For infrastructure projects, strategies focus on reducing material use through more efficient design and substitution of carbon intensive materials such as cement and bitumen with low embodied materials such as fly-ash and recycled asphalt pavement.
On the 103-kilometre section of the Melbourne to Brisbane Inland Rail project from Parkes to Narromine, around 7,250 tonnes of embodied greenhouse gas emissions were saved through use of carbon neutral precast concrete culverts supplied by material supplier Humes – a division of concrete and aggregates supplier Holcim.
On their $3.9 billion Rozelle Interchange and Western Harbour Tunnel Enabling Works road project in Sydney, meanwhile, the John Holland and CPB Contractors Joint Venture are using concrete which contains supplementary cementitious material (instead of Portland Cement) to the tune of 70 percent, recycled plastic fibres instead of traditional reinforcing steel and recycled crushed glass in place of virgin sand in flowable fill for tunnel drainage.
As mentioned above, the report noted that for some projects, embodied carbon reductions may achievable at little or no additional project cost.
This may be achieved, for example, by replacement of Portland cement with lower carbon materials such as mid-range levels of fly ash.
Nevertheless, it acknowledges that at least for now, other low carbon solutions may come with a slightly higher price tag. These may include geopolymer concrete, concrete admixtures, recycled materials, and high strength steel.
For this reason, the report cautions that reducing embodied carbon without adding to overall project cost may involve balancing some strategies which are cost negative with others that may be cost positive.
In its report, Edge said momentum behind reducing embodied carbon was being driven by a private investment market which is demanding sound environmental stewardship.
In some areas, governments are also acting.
On all of its projects that are worth $15 million or more, Transport for NSW requires reduction in construction related carbon emissions of at least five percent compared with a project baseline.
Meanwhile, the NSW Government has committed to ‘leading a national strategy to achieve net zero embodied carbon in building materials’.
CEFC CEO Ian Learmonth said the research demonstrated that sustainable building may not necessarily be more expensive.
“This important analysis shows that cost effective solutions can be implemented now to significantly reduce embodied carbon,” Learmonth said.
“Australian developers and builders don’t have to choose between sustainability and saving on costs.”