Carbon-negative concrete blocks could be made using magnesium from seawater

A magnesium-based cement produced using seawater could soak up carbon rather than emitting it like conventional cement. Although its properties make it unsuitable for reinforced concrete, the ‘carbon-negative’ cement could be used in non-reinforced materials, including concrete blocks, which comprise around 15% of all concrete applications.

Billions of tonnes of Portland cement are made each year, accounting for around 8% of global carbon dioxide emissions due to the process of heating carbon-containing limestone with fossil fuels to produce calcium oxide. Climate concerns mean efforts to find more sustainable alternatives are urgent.