‘Fired up by cleaner coal’

Published in The Weekender, August 2009

I want to visit Eskom’s proposed concentrated solar power (CSP) power station, but after 10 years of faffing, they’ve still not actually built it, and South Africa is now watching as India, California, Spain and Texas leave us in the solar dust.

The hills are afire: gas from the UCG plant will be piped to the Majuba Power Station near Volksrust.
The hills are afire: gas from the UCG plant will be piped to the Majuba Power Station near Volksrust.

So I’m visiting one of Eskom’s efforts to make old energy a bit less damaging. Eskom is very comfortable with coal, but like many of the world’s utilities, they’re under ever-increasing pressure to use less of it and dial back their enormous contribution to global warming. One of their latest efforts to make coal cleaner is a pilot project for underground coal gasification (UCG) adjacent to the gigantic Majuba power station near Volksrust in Mpumalanga.

The idea behind UCG is that instead of first mining coal, processing it, then burning it to produce heat and electricity, you set it alight underground to produce a stream of gas that can in turn be burned to produce electricity. Put like that, it sounds almost reckless, but if the technology meets the hopes of its advocates, it really should make burning coal less dirty.

Eskom, like its international counterparts, describes UCG as a “clean coal” technology. It’s one of a number of technologies it plans to roll out to reduce emissions but since they all still produce substantial quantities of pollutants, the term is misleading. “Cleaner coal” would be a more honest claim.

How does UCG work? The pilot site is on a small plateau amongst the long rolling hills of eastern Mpumalanga, 7 km from the imposing turbine halls and cooling towers of the Majuba power station. The site is on an old farm – the site office is the converted farm house, where project leaders Lou Duvenage and Mike Beeslaar work with their colleagues.

Three hundred metres below the winter-crisped grass on this little plateau lies a vast seam of coal that stretches many kilometres in every direction. Unminable by conventional techniques, the seam has been carefully selected for geological integrity; for instance, there are no cracks leading to the surface that might let in air and permit uncontrolled burning of the coal.

Eskom has drilled slim 15 cm wide wells, deep down 300 metres into the coal seam below. The seam is set alight using a mysterious and proprietary process. Eskom is licensing certain technologies from a Canadian company, Ergo Exergy, which employs engineers from the former Soviet Union. Their concerns about the security of these elements of the process make them unwilling to allow me to photograph the holes, poles and pipeline that constitute the project’s modest above-ground infrastructure.

Once the seam is alight, air and occasionally steam is pumped into the seam to fuel the fire, the part-burning of the coal in the presence of a small amount of moisture produces synthetic gas, a carbon monoxide-hydrogen combination. The resulting combustible gas pours out through another identical well. To stop polluted water leaving the system, the seam is kept in a state of relative negative pressure.

The hilltop is lightly scattered with interlaced dirt track, wooden posts supporting floodlights, and the beginnings of a small pipeline that will carry the small stream of gas produced here seven kilometres across the hills, where it will soon join the coal feed from the conventional mines that power Majuba.

A shallow plastic-lined pond holds recycled cooling water. “You should see it on winter mornings. It’s like a Jacuzzi, we have a hard time staying out of it,” jokes Duvenage.

Amongst it all, hardly noticeable, stands a vertical steel pipe, 15cm in diameter and about four metres high, with a narrowed, scorched neck. This is where the gases produced by the fire underground currently flare out, rather like a tiny oil well gas flare. Since the gas stream is not currently being used, the fire underground is kept turned down. If it went out, Duvenage says, it would take several days of hard work to get it going again.

Duvenage and Beeslaar are cautiously enthusiastic about the project. “It’s fun. Sometimes you want to take another 10 steps [towards production],” says Duvenage. “But you have to take it slowly, stick to just four steps. Research is about getting each step exactly right first.”

Those next steps include co-firing the gas stream from the pilot at the Majuba Power Station later this year. A 40MW demonstration plant should go online mid-2013, to be succeeded in turn by a proposed 2100MW full-scale power facility from 2017 if all goes well with the demonstration.

UCG is not a new idea – there were a number of working UCG facilities in the former Soviet Union, and the concept was proposed as early as 1868. Duvenage and Beeslaar are quietly scornful about failed US attempts at UCG at Hoe Creek, Wyoming, in the early 1970s. They suggest that the seam used was too shallow, leading to uncontrolled burning and groundwater contamination with highly carcinogenic benzene and phenols.

The Eskom pilot, much deeper, is surrounded by a network of monitoring wells to detect uncontrolled burning or leaking. “Aquifer contamination is Eskom’s biggest technology concern,” says Eskom’s UCG literature.

The process can exploit what would otherwise be unminable coal, effectively increasing South Africa’s reserves, while producing 16-25% less carbon emissions than do conventional coal power stations.

This seems to be an environmental strategic danger of the technology: it could massively extend reliance on coal, both in South Africa and globally.

For the meantime, UCG’s production of pollutants other than carbon dioxide is substantially lower. Emissions of particulates, sulphur dioxide and nitrous oxide (another potent greenhouse gas) are here reduced by a factor of around seven when compared with other coal-based technologies.

There is no attendant energy-intensive mining, crushing or transportation. And the process leaves the toxic, often highly radioactive flyash that is produced by a conventional power station, underground. Since the Majuba seam was ignited in [early 2007], there have been just a few millimetres of surface subsidence, according to Beeslaar.

It may even be possible to combine UCG with carbon capture and storage (CCS), and pump the carbon dioxide produced by the process back underground to keep the warming gas out of the atmosphere.

The other by-products from the process are potentially very useful: they include ammonia (which can be used in fertilizer) and a range of hydrocarbons which can be turned into automotive fuel. These by-products appear to be something of a headache for Eskom, which is in neither the fuel or fertilizer businesses, and must find other partners to manage these product streams. Not surprisingly, given the fuel production possibilities, Sasol recently announced its own UCG pilot at Secunda.

The Eskom pilot has helped create renewed international enthusiasm for the technology, and the site has been something of a place of pilgrimage, pulling visits from Australia, New Zealand, and a team of no less than 16 people from the office of California governor Arnold Schwarzenegger.

The labour implications of a move to UCG are significant, and Eskom is sensitive about this point. UCG could affect future coal industry employment, undermining part of Eskom’s rationale for its own existence, as stated in its application to the national energy regulator (Nersa) for its contentious recent interim price increase: “ensuring sustainability of the coal mining sector”.

[This version of the article is as filed, not as published.]

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David

I am an environmental writer, journalist and speaker living in Cape Town, South Africa.

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