Article by Tom Whipple, Science Editor at The Times 

Companies such as MCi Carbon are speeding up natural cycles and reusing the emissions from making materials including cement and paper.

The geological carbon cycle is not quick. The time taken for minerals in the land and sea to react with carbon ­dioxide, locking it into rock, is measured in years, often many years.

Unless, that is, it is in a bubbling vat that will be constructed in Austria.

A clean energy firm said this month that it plans to do in an hour what the Earth achieves in geological time — and to help decarbonise heavy industry.

MCi Carbon, an Australian company that won the clean energy start-up prize at Cop26 in Glasgow in 2021, has announced plans to build a plant in 2028 that, it hopes, will not only capture 50,000 tonnes of CO₂ a year from industrial processes but will turn it into building materials.

It is one of a number of companies trying to tackle one of the more intractable problems of climate change: dealing with the construction industry.

Not only does making building ­materials require vast amounts of energy, but the release of CO₂ is, in many cases, intrinsic to the chemical process. Of every 25 molecules of CO₂ emitted by humans, about 2 come from cement production.

Working with RHI Magnesita, an Austrian materials company that specialises in high-temperature carbon-intensive processes, MCi Carbon aims to show that it can first capture carbon emissions from those industrial processes at scale, then use them to make carbon-negative building materials.

It is doing so by speeding up geology. Given time, minerals such as magnesium and calcium react with CO₂ to make carbonates. Sophia Hamblin Wang, co-founder of MCi Carbon, said that, in their system, “reaction time has come down to a matter of minutes”.

They have a slurry of minerals in a vat and “you literally just attach it to a chimney or flue and then bubble through the raw flue gas”. Depending on the mineral composition of the slurry, which can come from industry and mining waste, the resulting product can be used to make paper, plasterboard and cement.

If MCi’s approach is to make chemistry faster, others are looking at biology. Bert Bruggeman, chief executive of Biomason, another leader in carbon-neutral building materials, said they began with the goal of “using nature to build the things we need as humans”.

There are plenty of strong natural constructions, such as coral reefs, that don’t require 1,000C furnaces. “How can we use micro-organisms to start industrialising the process that happens in corals?” Bruggeman asked. In the end, Biomason alighted on bacteria that make calcium carbonate in limestone caves.

Working with IBF, a Danish concrete maker, they are supplying bacterial ­labour to make concrete tiles without heat or CO₂ expulsion. “The bacteria show up dormant,” Bruggeman said. “We wake them up and insert them into a traditional precast concrete factory.” They are fed urea from an ammonia plant and within days start to build a structure around a granite aggregate.

Whether the industry will be decarbonised using geology, biology, both or neither will come down to cost, he said.