Transforming construction from carbon emitter to carbon sink

By Alex Xing, Andreas Bremen, Co-Founder, Co-reactive

Shelter is a fundamental human right. As the world population rises, there is an ever-growing pressure to provide it, and our cities are sprawling to meet the demand.

But the tried-and-tested materials we use to build our homes, schools and hospitals come with a massive carbon footprint – some 11% of the world’s total. Cement alone is responsible for 8%.

The urgent demand for housing and limited availability of sustainable materials make decarbonizing this sector a uniquely complex challenge, but one that innovators around the world are responding to.

As someone who has dedicated my career to tackling it from the technical side, I believe a net-zero future for construction is possible. But there are three urgent obstacles we must address to get there.

First, we need to rethink the materials we build with.

Concrete is the second-most used material on Earth, after water. It’s an essential part of virtually all modern buildings and infrastructure, whether for foundations or walls. There is a simple reason why: it works.

Concrete is strong and versatile, resistant to both fire and weather. Most importantly though, it’s highly cost-effective. So, rather than replace this ubiquitous material outright, how can we substitute its constituent ingredients while maintaining those useful properties?

This is a question I asked myself during my PhD and time in industry – one that led me to co-found Co-Reactive.

Cement is the glue that binds concrete together. Its most important and carbon-intensive component is called clinker, made up of limestone and clay. We have developed a carbon-negative alternative material (CO-SCM) that can replace significant amounts of clinker in each cement mix. Carbon dioxide – sourced from industrial carbon capture, biogas plants and other sources – is locked into our material during the manufacturing process. Every ton we produce stores 330kg of CO2.

Elsewhere, innovators are developing sustainable alternative materials. Some are developing concrete components made from circular materials, like cement made from recycled building waste. Others are finding new ways to use regenerative materials like timber and bamboo for large-scale buildings.

Many of these promising innovations have the technical potential to move the industry towards carbon neutrality. But they face common challenges.

Second, we must scale up innovations at an unprecedented pace.

To put this into perspective, we are currently scaling our capacity from 10 to 1,000 tons per year with our first demo facility; one single cement plant can produce up to 1 million tons per year.

Scaling is also dependent on an equally rapid expansion of the infrastructure to collect, process and deliver waste material. In our case, that’s carbon capture facilities, but circular materials require sophisticated demolition waste processing and timber needs sustainably managed forests.

Cost, though, is the central factor. Sustainable materials must be cost-competitive with what is already available, or builders – who operate on thin cost margins – will not be able to use them. The challenge is acute in developing countries, where populations are growing faster while building budgets are tighter. Innovative materials often have high R&D costs, and they are competing with long-established production methods and supply chains, so inevitably they come with higher initial costs.

All of these challenges will diminish as the technologies develop. But effective policy can accelerate the process.

Third, we need smart policy and investment to make sustainable materials mainstream.

The EU’s Emission Trading Scheme (ETS) is a strong early example. Its emissions cap puts a price on CO2, incentivizing high-emitting companies, including cement producers, to decarbonize their operations. Companies that exceed the cap will be mandated to buy credits from those who remain below it or face fines, in effect rewarding sustainable practices. Those that do not start transforming today will see costs skyrocket and conventional concrete increasingly unviable to produce.

Measures like this build the business case for sustainable construction and drive investment into green innovations like ours. They are a good low-cost policy option for governments, but they are just a start.

To scale innovative materials at the rate needed to meet net-zero goals, they must be complemented with changes to building regulations and targeted investment in the necessary infrastructure. Only through these bold steps will we transform the industry from one of the world’s largest emitters into a carbon sink.

It will take ambition on a global scale to decarbonize hard-to-abate industries like construction. Groundbreaking innovations prove that humanity has the ingenuity to take on this momentous challenge. Now is the time to match that ingenuity with scaled investment, enabling infrastructure, and forward-thinking policy. With the right momentum, we can lay the groundwork for truly net-zero cities.