The Case for Direct Air Capture: De-Fossilising Cement Production

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December 6, 2021

The International Energy Agency has identified emissions from industries like cement, iron and steel — accounting for one-quarter of global CO2 emissions — as being some of the most challenging to abate, or eliminate. Our previous features focused on de-fossilising aviation and shipping. If you haven’t read those already, they are well worth a quick 2-minute read...even if we do say so ourselves.

Cement is found in everything - from the roads we drive on, to the bridges we cross, and the buildings we live and work in. Cement production currently accounts for 8% of global CO2 emissions — triple that of aviation, or the 3rd largest global emitter if the industry were a country, behind only China and the USA. While around half of emissions are associated with the chemical process itself in the breakdown of limestone (CaCO3) into lime (CaO), the other half of emissions are largely associated with the energy required to produce cement, the binding agent in the production of concrete. Those energy related emissions can be abated using conventional carbon capture technologies. However, this will by no means be sufficient to eliminate the climate impact of an industry accounting for almost 1 out of every 10 carbon emissions globally.

This has sparked a necessity to develop alternatives to current techniques of cement production; or hybrid and even entirely different materials. Some have touted the use of wood-based alternatives, particularly for small-scale construction use. Other alternatives include geopolymer-based cements, which do not use calcium carbonate (sourced from limestone) as a main ingredient, and claim to reduce emissions by 80–90% compared to conventional cement. Bacteria has also been used to grow cement bricks which exhibit the same properties as conventional bricks, however are carbon-sequestering.

Direct air capture (DAC) is also a technology with broad applications in de-fossilising cement production. This includes adoption in more industry accepted alternatives like ‘carbon-cured’ cements. These cements can absorb the CO2 captured through DAC rather than water as they harden, while also strengthening the final concrete product. If this CO2 absorption can occur at a higher rate than the CO2 released during their production, cement can become a carbon sink, or technically carbon-negative, rather than a significant source as today.

Such carbon enriched concrete is one of the products we are exploring at Carbon Infinity using the CO2 captured from our air capture technology. While demand for materials like concrete is only set to increase with advancing levels of urbanisation and economic development, alternatives like synthetic and carbon-cured concrete must be developed as we decarbonise our economies, industries and tackle the climate crisis.

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