Where there is coal, there is gas – a deadly hazard to early miners, who carried canaries with them to warn of its poisonous presence.
Now, southern African countries hope to harvest this nuisance as a source of energy.
The region has plenty of coal. South Africa alone produces 225 million tonnes a year, exporting a third of it. Landlocked Botswana and Zimbabwe also have huge reserves, but the cost of railing it to ports makes mining it uneconomical.
In addition, the environmental danger it presents are now well documented, and it is among the world’s least favourite commodity. This means the regions’ coal industry has to look at alternative ways to survive, especially in a climate where commodity prices are on the floor.
“Coal miners are hanging on the edge and are facing tough decisions,” says Liz de Klerk, a Venmyn Deloitte mining advisory manager and coal specialist. “They are going to have to be creative, or shut up shop.”
South Africa has about 30 billion tonnes of mineable reserves, according to the Chamber of Mines, enough for another 100 years using current technology. The total resource, however, is three times that but much of it will probably stay in the ground as low prices, environmental concerns and uncooperative geology conspire against its liberation.
An alternative to scooping it out of the ground is to harvest the gas it produces.
This is formed when ancient plant material rots and is compressed over centuries, forming coal and gas. Crude oil is formed much the same way and, as with coal, gas has long been an unwelcome by-product of crude extraction; often this is flared to prevent it from building up to dangerous levels during the oil extraction process.
Coal miners now hope to harvest it rather than vent it out, using several different technologies. Gas can either be extracted via drill wells, much as it is in other areas such as Qatar or the United States; another way is to combust the gas, which in turn burns the coal seam itself, giving off a much larger volumes of gas. This is then harvested via another well, to be used on the surface. Harmful emissions can also be captured and returned underground for permanent storage.
“Now everybody is looking at this,” says Ms de Klerk. “We are seeing some of the bigger players with money and intent looking at these alternatives.”
Underground coal gasification (UCG) in particular is of interest to miners; it works by injecting air and steam, via a well, deep into the ground and igniting it. The gases given off by the combusted coal seam are extracted through another well, and can be used to run conventional turbines or stored for other commercial purposes.
Trials are already being carried out in Australia, a major coal producer, and Uzbekistan, with Russia and India also among those looking at the technology.
“UCG is a major ‘cleaner coal’ opportunity for us as some of our coal seams are uneconomic to mine due to poor quality, and sometimes depth,” says Professor Rosemary Falcon, an executive member of the Fossil Fuel Foundation of South Africa.
The foundation was formed a few years ago specifically to look at alternative coal-gas extraction possibilities.
The process will allow the monetisation of deep-level seams that are difficult to access; gas build up, the bane of coal miners, increases as pressure grows because of depth, but UCG turns it into a plus rather than a negative. Miners will therefore no longer be sent into the perilous depths; instead, energy extraction will take place entirely from the surface.
It also has environmental benefits. When the coal burns, it releases a synthetic gas, which mainly includes carbon monoxide, hydrogen, methane and carbon dioxide. The useful items such as methane and hydrogen are extracted at the surface, while the harmful elements will be returned underground for permanent storage.