• Eirini Sampson

The role of cement and steel in a net-zero world

If a net zero world by 2050 is feasible, cement and steel come to play a determining role in the direction we are moving to.

Cement and steel are the essential ingredients needed for buildings, dams, bridges, skyscrapers - you name it; but the industry is one of the dirtiest in the world, with 2.3 billion tonnes of CO2 being emitted each year as a result of cement production, and the release of 2.6 billion tonnes of CO2 per year due to the production of iron. Each making up about 7% of global CO2 emissions. This combined with the exponentially increasing industrial demand as a result of rapid urbanisation makes an unfortunate pair for global net-zero efforts.

Between the energy they need and their construction, buildings make up roughly 40% of global emissions according to the IEA.

“The only thing we use more as humans is water,” says Jeremy Gregory, executive director of MIT’s Concrete Sustainability Hub.

The difficulty behind cement and iron is the energy intensity needed for ultrahigh temperatures, which are difficult to get from renewable energy alone. Given that the lifecycle of cement and steel plants can span beyond 50 years, several scientists make a case for carbon capture and storage technologies.

Electra - a Colorado-based startup has developed a new way of making emissions-free iron by making it at 60C instead of 1,600C inside a coal-fired furnace. The report from the 2019 GGSD Forum on low and zero emissions in the industry found - amongst others - that the most effective way to reduce steel and concrete emissions is to use them only for necessary applications in new products, vehicles and structures which would have a -25 to -50% emissions reduction potential. Further, the reports found that the first step to reducing emissions from steel is to maximise the volume and quality of recycling. Other technology-related barriers were reiterated, but the report also argued that policy to address market conditions, behaviour and political economy challenges will be equally as important as the industries are highly competitive with difficulties in passing on costs. Installations are key elements of local supply chains with high indirect capital and employment values added. As a result, there is no existing market that is ready to pay the premium for low emissions steel, while policymaking in the field is lacking, leading to inconsistent guidance for cement and steel firms and the creation of what the report labels as an investment limbo.

Paul Fennell, Justin Driver, Christopher Bataille and Steven J. Davis of Imperial College London, set out 9 steps to get to net zero in the industry in their article for Nature. According to this, carbon capture (taking CO2 and locking it away underground) wil be essential in lowering cement-production emissions. An issue they find in this is that the stream of CO2 must be more than 99.9% pure to reduce costs of compressing and storing the gas - while steel and cement plant fuels usually consist of about 30% CO2 (the rest being nitrogen and steam). The authors argued that storing CO2 can make cement stronger which will, in turn, reduce the amount of cement needed in a structure and its net emissions by around 5%. As with the abovementioned report, the ninth step in reaching net-zero is subsidising changes to encourage technological innovation and implementation at pilot to early commercial stages, as low carbon products lack competitive advantage and markets. An added hurdle to this is that developing nations, where most construction is happening, need the technology and the know-how to be shared and the implementation mechanisms to lessen related financial risks.