Andreas Späth

Will Eskom ignite the ground beneath our feet?

2014-04-07 08:58

Andreas Wilson-Späth

If you think that mining shale gas by hydraulic fracturing (fracking) is the only innovative way the fossil fuel industry is planning to get at the carbon currently locked away under our feet, I’ve got news for you.

One method of extracting subterranean fossil fuel reserves that has been flying under the radar of the mainstream media for several years is ready to expand from the trial stage into the big league and Eskom is at the forefront of making it happen.

It’s called underground coal gasification (UCG) and it has the potential to become a game changer - in a good way if you’re a coal-based energy company; in a disastrous way if you care about climate change.

Eliminating the need for digging coal out of the earth before burning it in power plants, UCG essentially works by igniting coal seams where they are under ground. The gas that’s produced is brought to surface where it can be used to generate electricity or turned into a variety of products.

On paper, the process is pretty straight forward. A vertical well is drilled into a layer of coal as deep as 2000 metres below the surface. From there, holes may also be drilled horizontally along the base of the coal bed.

Oxidants in the form of air, oxygen or steam are then pumped into the vertical injection well to ignite and fuel the coal which burns to produce carbon dioxide, hydrogen, carbon monoxide, methane and various other volatiles including hydrogen sulphide, sulphur oxides and nitrogen oxides.

These combustion gases are transported to the surface via one or more additional vertical production wells where they can be separated and used to generate electricity in power plants or converted into synthetic fuels, fertilizer and other chemical products.

Eskom has been operating a UCG demonstration plant at its Majuba coalfield and power station in Mpumalanga for several years and is ready to expand the process.

Sasol and others have also experimented with UCG trials and the Department of Energy has indicated that the country should exploit the technology on a larger scale.

Eskom and others tout UCG as “clean coal technology” because it:

- has a much smaller surface footprint than conventional coal mining operations – in fact it requires no mining at all;

- eliminates solid waste at the surface, particularly the ash produced by burning coal in power plants;

- reduces the emission of sulphur and nitrogen oxides; and

- promises lower global warming impacts since carbon dioxide could potentially be captured and stored underground in the space left by the burned out coal seam.

So what’s the problem?

Critics point to a number of issues, including potential air pollution from escaping gasses, ground subsidence at the surface, and possible groundwater contamination by volatile and toxic organic compounds that remain below ground after the gasification process.

But the biggest concern is the very thing that makes UCG so attractive to Eskom and others in the first place: the fact that it opens up vast coal reserves that have been inaccessible to commercial exploitation until now.

Layers of coal that were previously unprofitable or impossible to get to because they were too low grade, too deep or too thin to be mined conventionally can now be exploited by UCG.

For those in the fossil fuel business, this means huge potential profits which were formerly out of their reach.

In South Africa, conventionally recoverable coal reserves are estimated at about 34 billion tons. The use of UCG could increase that amount by as much as an additional 45 billion tons. Globally, the amount of coal believed to be accessible to miners now is around 3 trillion tons, while UCG could balloon that figure by between 4 and 15 trillion tons.

UCG could extend the planet’s supply of coal power by centuries.

We know, however, that if we burn just the coal that is currently exploitable, our chances of avoiding catastrophic climate change with dire consequences are minimal.

If we allow Eskom and others to get at coal deposits that have been safely out of their grasp until now by using UCG technology, we are well and truly fried.

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