The Industrial Revolution left a deep mark on our world. Its dawning saw the start of the widespread burning of coal for factories and steam engines and, as a result, the beginning of significant outputs of carbon dioxide into the atmosphere. Our climate is now warming noticeably as these emissions have accumulated across the planet.

The British landscape has also been changed dramatically. In particular, the countryside is now peppered with piles of slag left over from old steel mills. Landscaping these piles of industrial waste has required major efforts by local authorities in recent decades.

But now a British scientist is planning to use slag heaps to deal with the climate change. Based at Cardiff University’s school of earth and ocean sciences, Phil Renforth is preparing to test the feasibility of using iron and steel slag deposits to remove carbon dioxide from the atmosphere. His three-year project, which has just been awarded a £300,000 grant by the Natural Environment Research Council (Nerc), is set to begin in Consett, County Durham, and Port Talbot, south Wales.

Renforth’s first step will actually be to make more of the industrial waste piles. “The aim is not to use old slag heaps to remove carbon dioxide from the atmosphere, but to carry out trials that will show how we can extract carbon dioxide from the atmosphere by pumping air through newly created slag heaps,” he told the Observer last week.

During the process of steel-making, iron ore is mixed with limestone or dolomite and heated to extremely high temperatures. The end results are steel and slag, a waste mixture of calcium and magnesium silicates and oxides. Piles of this ore-processing leftover have been dumped around the countryside over several centuries.

“Often these heaps have been landscaped very nicely,” said Renforth, who has worked on the project with Will Mayes of Hull University. “There is one in Consett that has been turned into lovely parkland where people can walk their dogs. They are all round the country. Wherever we have made iron, we have left a pile of slag.”

Earlier research by Renforth has shown that carbon dioxide from the atmosphere is absorbed by material inside slag heaps. “We now want to see if we can improve the rate of this absorption so that can we make significant reductions in atmospheric levels of carbon dioxide in the future,” added Renforth.

To do this, Renforth’s project will proceed in two stages. “First, we will drill into one of these old, historic slag heaps and see what has been happening there over the years and understand what chemical processes have been going on as rainwater has brought carbon dioxide into the heap.

“And then we will start the second stage. We will create our own mini-heap – about the size of a skip – and play with its chemistry to try to optimise its ability to sequester carbon from the atmosphere.” These slag-based carbon sequestrators could then be used as models of larger devices that could reduce carbon levels in the atmosphere, Renforth added.

The UK produces 3-4m tonnes of slag a year while the total global production is estimated as being about 500m tonnes a year at present. However, this rate could increase as developing nations catch up, added Renforth. “Our calculations suggest that we might produce between 100bn and 200bn tonnes of slag cumulatively by the end of this century,” added Renforth. “That has the potential to remove 50-100bn tonnes of carbon from the atmosphere, we believe.”

Phil Renforth (left) surveying the slag tips in Consett. Photograph: Peter Brabham

Finding effective ways to achieve carbon dioxide extraction – or sequestration, as it is also known – is considered to be of vital importance in stabilising global warming to below 2C. While the burning of coal and oil for electricity generation can be substantially replaced with the use of renewable or nuclear energy sources, scientists say there will still be a need to burn some forms of fossil fuel – for the aerospace industry, for example – and this use will continue to add carbon dioxide into the atmosphere. So finding ways to suck it out – to balance this continued output of carbon – could still have a very important role to play in limiting climate change.

“We are going to have think about ways of not just limiting carbon emissions but of actually removing greenhouse gases from the atmosphere and it may well be that technology based on slag leftovers from the steel industry could play a key role,” added Renforth.