Concrete cancer - what's the cure for 9% of global emissions?

More concrete is made by humans than any other product on Earth and with that voluminous output comes almost a tenth of all human carbon dioxide emissions.

Every kilogram of cement that is made sends a kilogram of CO2 into the atmosphere.

While cement and concrete have essentially been made the same way for a century, new techniques utilising alternative materials and processes do offer hope for a greener concrete future.

Studies by University of Colorado Boulder and published in the international journal Scientific American show that cement and concrete production account for around 9 per cent of all emissions. Around 4.3 billion metric tons was produced globally in 2021 and that figure is expected to grow by around 20 per cent by 2050.

While Australia is making some progress towards decarbonisation, there is the potential to make a huge impact in the construction industry – which, globally, is responsible for 40 per cent of the world’s annual greenhouse gas emissions.

A new report by Hatch, who oversee engineering, operational and development projects in the metals, energy, and infrastructure industries, has found that ‘green concrete’ has the eco credentials to be a key driver in reducing Australia’s emissions.

Dr Ezgi Kaya, Structural Engineer, Hatch Australasia

Dr Ezgi Kaya, a structural engineer at Hatch Australasia who co-leads initiatives on low-carbon concrete and parametric design, said green concrete is a sustainable and environmentally friendly alternative to traditional concrete and an excellent solution for reducing carbon emissions in the construction industry. 

“Unlike conventional concrete, which requires a considerable amount of energy and resources to produce, green concrete often uses recycled materials and minimises the use of Portland cement, a major contributor to carbon emissions.

“To date, green concrete has been used in more than 60 projects across different sectors in Australia, including infrastructure, buildings, industrial, marine and geotechnical.

“Given that the carbon reduction achieved through its use can be as much as 80 per cent, the potential for green concrete to positively impact our emissions targets is monumental.”

Hatch’s Green Concrete review found that the cost impact of using green concrete in a structure is almost negligible. It would add up to 1.4 per cent in total installation cost compared with traditional concrete.

It can be placed and pumped like traditional concrete and minimises landfill disposal through recycling the industrial wastes, such as fly ash, furnace slag and silica fume.

Dr Kaya said Australia is a country that has a vast potential for green concrete usage, thanks to its abundance of resources such as recycled aggregates, fly ash and slag. These materials can be used as a replacement for traditional aggregates and cement, making the production of green concrete more sustainable and eco-friendly. 

“Replacing just 50 per cent of traditional concrete with green concrete could reduce Australia’s carbon emissions by approximately 17 million tonnes annually, which is equivalent to removing four million cars from the road.”

Scientific American reported that trials have shown that a portion of the cement in a mix can be replaced with calcined (burnt) clay or ingredients made from wastes such as fly ash and slag without a loss of strength and with fewer emissions.

The use of green concrete is already gaining traction around the world. It has been used in the construction of high-profile buildings such as the Louvre Abu Dhabi and Amsterdam’s Schiphol Airport. 

Carbon budgets in the build planning stage

The Australian Institute of Quantity Surveyors (AIQS) is calling for embodied carbon budgets to be introduced into all future construction projects with the goal of reducing upfront carbon emissions by at least 40 per cent to achieve Australia’s 2030 carbon emissions targets.

Australia’s 2030 carbon emissions target is to reduce greenhouse gas emissions by 43 per cent below 2005 levels by 2030, which is a 15 per cent increase on Australia’s previous 2030 target. This is in line with Australia’s commitment to net zero emissions by 2050.

Under the proposal, all new builds and major refurbishments would be required to have an embodied carbon budget integrated into the projects’ construction cost budget from the outset, to ensure the best possible balance between cost and sustainability outcomes.

“This approach allows for the development of an optimal balance between cost and sustainability,” Simon Squire, AIQS Director, said.

“To have effective control of carbon reduction, measurement is imperative.”

As a key member of the project team, a quantity surveyor develops both the initial baseline estimate for the cost and upfront carbon emissions.

“To achieve a 40 per cent reduction in Scope 3 carbon emissions from 2020 levels, it is crucial for the client to establish the right target in the project brief and involve the supply chain early in the design phase with the right professionals,” Mr Squire said.

He added that quantity surveyors are also best placed to monitor and quantify both the carbon and construction budgets throughout the design process.

“It is time for the wider construction industry to balance its view on cost and environment,” concluded Mr Squire.

Green Building Council of Australia’s Chief Impact Officer, Jorge Chapa said the construction industry is encountering challenges and recognising the importance of changing course to achieve reductions in upfront carbon emissions.

“A quarter of a building’s emissions are locked in on the first day the occupants walk through the front doors.

“Every project team gets just one shot to reduce the upfront carbon of their next building, so we welcome all efforts to ensure carbon reductions are considered at the outset of all projects,” he said.

Green concrete, red tape

Challenges do remain in having green concrete produced in meaningful quantities that will reduce emissions.

There is still not enough supply of the alternative materials to meet demand.

Wil V. Srubar, Associate Professor of Architectural Engineering, wrote in Scientific American that some methods are spreading while others were still experimental.

“Because most cement and concrete is made locally or regionally and close to where it is used, the availability of substitute materials, as well as revised building standards to allow their use, capital costs for retooling and market acceptance are all practical challenges.”

New building codes that force all new Australian homes to comply with tougher energy performance standards came into effect on 1 May, with a transition period granted to 1 October. The changes are expected to cut the thermal energy use of homes by about 25 per cent.