Slag: "A Stony Waste Matter Separated from Metals During the Smelting or Refining of Ore", may be another solution in the fight to reduce Global Warming CO2.

The tech race to save Earth from CO2

In 2008, a young British ­researcher discovered something that might help us to slow down or even reverse climate change. Dr Phil Renforth, now a lecturer in the School of Earth and Ocean Sciences at Cardiff University, was analysing water seeping from the bottom of the slag heaps at the former steelworks in Consett, County Durham, when he found it had a high concentration of carbon.

From article, (In 2008, a young British ­researcher discovered something that might help us to slow down or even reverse climate change. Dr Phil Renforth, now a lecturer in the School of Earth and Ocean Sciences at Cardiff University, was analysing water seeping from the bottom of the slag heaps at the former steelworks in Consett, County Durham, when he found it had a high concentration of carbon. This might not sound like much, but it was evidence that the slag left behind by the iron and steel industry, and other similar industries, can remove carbon from the atmosphere in the same way that natural rocks can. In a process known as the “carbonate-silicate cycle”, the silicate rocks common on the Earth’s surface, such as granite and basalt, play a key role in controlling the amount of carbon dioxide in the atmosphere and oceans by removing CO2 from the atmosphere and turning it into carbonate rocks such as chalk and limestone.

Last summer, Renforth was back at Consett to drill boreholes 45m (148ft) deep to find out just how much CO2 the slag had absorbed – and, he says, “the data is looking pretty exciting. It is suggesting that our hypothesis is right. The slag heaps are capturing CO2, but not as much as we think they can because they are grassed over and sealed off from the atmosphere. This means that they have the potential to capture even more. “There are about 16 million tons of slag in that heap,” he adds. “The rate of capture is about half that, so one heap could store about 8 million tons of carbon. Globally, the iron and steel industry produces about half a billion tons of slag each year, so that means about a quarter of a billion tons of CO2 could be captured from the atmosphere.” If, that is, Renforth can find a way to turn the new slag heaps produced worldwide into giant carbon capture and storage machines on a scale that is “climatically relevant”. The use of the slag in this way is just one way in which carbon removal from the atmosphere might work. Renforth’s research is part of the £8.6m Greenhouse Gas Removal (GGR) programme run by the UK’s Natural Environment ­Research Council. It is one of the first such programmes in the world to explore the viability of the new technologies that are aiming at negative emissions of gases such as carbon and methane.
Dr Phyllis Lam, associate professor in microbial biogeochemistry at the University of Southampton, works closely with Redfern. She has been looking at whether friendly microbes could be used to speed up this process by enhancing the dissolution of CO2, by turning it into organic matter or even limestone. Lam hopes to build a pilot plant shortly. Speeding up this process may not be as difficult as it sounds. Last summer, on a brownfield site in Newcastle, Renforth and his team made another surprising discovery. “The demolition rubble that had been spread out over the site had absorbed 80 or 90 per cent of its carbon in five years.” “Some people have called carbon reduction a benign form of geoengineering, but I wouldn’t call it that,” says Dr Niall MacDowell, who leads the Clean Fossil and Bioenergy Research Group of Imperial College London. “We have been bad house guests and it is a way for us to clear up after ourselves.)

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