As global industry attempts to decarbonise its energy-intensive processes such as cement manufacture, could the key to decarbonisation lie in the rocks beneath our feet?

Experienced industrial gases expert Stephen B. Harrison spoke with gasworld during its Europe CO2 Summit 2022 and delved into an area considered one of the most exciting in current CO2 applications – utilisation, specifically in the area of mineralisation.

Enthused by the prospect of CO2 for mineralisation, Harrison explained that that some rocks, such as limestone and magnesite are saturated in CO2. During cement manufacture limestone converts to calcium oxide, releasing CO2 in the process. Two specific ultramafic rocks, serpentinite and olivine are able to absorb CO2 during mineralisation. 

“These ultramafic rocks are interesting because they can help us to absorb CO2 to take CO2 out of the atmosphere.” 

“We can use these rocks to help decarbonise industrial processes,” he added. 

Once these rocks are mined, mass-transport and a cost effective logistics infrastructure is required to move the load to the location where CO2 needs to be captured.

On location, the rocks must be milled to powders to react quickly with CO2 in mineralisation reactions. An energy-intensive process, Harrison said, “Carbon capture through any technology doesn’t come for free.” 

Recycling mine tailings

Used to extract metals from mined ore, mine tailings – grit, dust, dirt, sediment – is already ground up and therefore could be a potential source of minerals to absorb CO2. 

Slag can also be used to help absorb CO2 using CO2 mineralisation to help reduce emissions for blast furnaces. 

Giving another example of slag that can be utilised, Harrison said, “Waste incineration slag is also suitable to absorb CO2 from industrial processes.” 

To make cement, limestone is required and a huge amount energy is needed to grind the limestone. Through the use of calcium carbonate, produced from mineralisation, industry can avoid the energy-intensive grinding process and reduce transportation and energy costs. 

Sea-level rise and climate change 

As atmospheric CO2 levels continue to proliferate and ambient temperatures increase year-on-year, sea-levels will continue to rise. These rising sea levels will neccesitate the need for more sea defences in many areas of the world. 

“So many cities have been built up on coastlines, very close to sea-level,” said Harrison. “As sea-levels rise through climate change, unfortunately we’ll need a lot of sea defences.”

While sea defences become more ubiquitous, larger amounts of concrete - and therefore cement - will have to be utilised.

“The need for cement is not going to go away as we seek to decarbonise,” he added.

”If we’re using that captured carbon to make cement, we’re capturing, utilising, and permanently storing carbon dioxide.”

All sessions of gasworld’s virtual ‘Europe CO2 Summit’ will be available to watch on-demand.