The tech race to save the Earth from global warming from CO2

 

Could slag heaps be used to help prevent climate change?

 

Read my latest #longread and double-page colour spread for the award-winning i paper in full below. You can read it online here.

It was also one of the stories featured in the i paper’s Essential Daily Briefing email.

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.

 

Grassing over and returning slag heaps to nature actually inhibits the process of carbon capture
Grassing over and returning slag heaps to nature actually inhibits the process of carbon capture

 

Carbon dioxide is one of the main gases that is helping to cause climate change by raising the temperature of the planet. In April 2017, CO2 reached levels in the Earth’s atmosphere not seen for millions of years.

Why we need to tackle carbon

Carbon dioxide (CO2) is not a pollutant but a naturally occurring gas that is essential for plant life. It is a greenhouse gas that helps to trap heat in the Earth’s atmosphere and keep the planet warm.

However, the burning of fossil fuels releases too much CO2 into the atmosphere, trapping more solar heat and leading, most agree, to global warming.

Warmer temperatures affect weather patterns and water supplies and cause sea levels to rise. They can also lead to more frequent severe weather events. The effect is long-term, as CO2 remains in the atmosphere for up to 200 years.

The 2015 Paris Agreement pledged to keep global temperature rise this century well below 2°C and pursue efforts to limit the increase to 1.5°C above pre-industrial levels.

To achieve this, the Intergovernmental Panel on Climate Change assumes that, as well as emissions being reduced, carbon will be taken out of the atmosphere.

The UN says new carbon technologies need to be developed now if we are to bring them online by 2050.

‘The data is looking pretty exciting’

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.

Some of the 100 researchers that the project is funding are looking at how to make the soil ­absorb more carbon or the feasibility of enlarging the lungs of the planet by simply planting more trees. Others are exploring more complex processes that involve carbon reduction and carbon capture and storage by harnessing the power of photosynthesis itself.

It involves what’s been called “carbon farming.” Farmers plant millions of acres of fast-growing trees and plants such as switchgrass that would replace the CO2 in the atmosphere with oxygen. These could then be burnt in a power station where the carbon dioxide produced would be caught before it entered the atmosphere and stored perhaps in disused oil and gas wells in the North Sea.

 

Carbon farming is another potential technology that could help
Carbon farming is another potential technology that could help

 

Alternative hopes

The GGR programme isn’t the only game in town. Eleanor Campbell, chair of chemistry at the University of Edinburgh, and not part of the programme, is considering how new materials that her laboratory is creating could be used on the roofs of people’s houses or on motorway barriers to soak up CO2 from the atmosphere like a sponge. Other researchers are exploring genetically modifying everyday crops to absorb more carbon.

Carbon Engineering near Vancouver, part-owned by Bill Gates, is one of the pioneers of a technology called direct air capture, which sucks roughly a ton of CO2 directly from the air every day and turns it into calcium carbonate pellets. These are subsequently heated, the gas forced off and stored in canisters.

The challenge for scientists who, like Renforth, are looking at using waste from industries including steel, mining, demolition and even cement manufacturing, is simply time. “Unfortunately, the time scale for these processes is hundreds of thousands of years, and the time scale that we need is hundreds of years or less,” says Simon Redfern, professor of mineral physics at Cambridge University. Redfern’s research into the use of mine waste to remove carbon took him to mines in Oman that date back thousands of years. “We are looking at nature to see whether there are mechanisms that we can employ to naturally accelerate the weathering of rocks without the use of much additional energy.

“You can play around with the temperature and pressure to see if it has any effect on the speed of the reaction,” he adds, “and you can employ biology to see if that can help with the chemical reaction.”

Could the process be speeded up?

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.

“£8.6m is a lot from an academic research perspective, but when you consider that a power station such as Drax would cost as much as £1bn to get it up and running, then £8.6m is a small amount of money. However, the project is asking interesting questions about which technology might work.

“We have done some work recently that suggests that having everyone optimise their little corner isn’t the best way to do it. It is perfectly possible to grow biomass in Brazil and ship it efficiently to the UK where it is burnt and the carbon released stored.”

The carbon removal business may have the potential to be worth trillions of pounds one day, but for now it consists of a lot of research and a handful of small pilot projects

. “There must be 50-60 ideas about how to remove carbon and some of them won’t work, some will only work in some places, and some will work everywhere,” says Renforth. “The question is, can they all work together quickly enough?”

 

 

 

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