Underground Coal Gasification: Hellfire and Damnation

The tidal wave of extreme energy methods that are bearing down on the British Isles are a desperate attempt to sustain a system that demands infinite growth on a finite planet. Nothing embodies that desperation better than Underground Coal Gasification (UCG). Since this insane method of fossil fuel extraction was first proposed in 1868, attempts to implement it have resulted in massive contamination of the environment with highly toxic chemicals and the eventual abandonment of the testing. Only in the case of the Soviet Union in the 1960s was UCG pushed forward into full production at a handful of plants in remote areas. Only one plant in Uzbekistan continues to operate. In the rest of the world sporadic attempts at testing of UCG over the last few decades have generally ended very badly.

Rocky Mountain Field Test of UCG near Hanna, Wyoming (1987-1988)

Underground Coal Gasification (UCG) involves utilising the drilling technology normally associated with oil and gas extraction to get access to coal that is not possible to mine with conventional means (tunnels or open cast). Since you cannot pump solid coal up a well bore it needs to be first converted into a liquid or gas. The simplest way of doing this is to set it on fire which will obviously turn it into a gas. Oxygen is needed for the coal to burn so air (or pure oxygen) has to be pumped down into the coal seam. If the coal is completely burned then the gas produced would be carbon dioxide which would not be particularly helpful in terms of generating energy. If however the amount of air/oxygen is limited such that the coal only partially burns, carbon monoxide will be the main combustion product which can then be piped to the surface and burned there.

Clearly this is not going to be a particularly efficient process since much of the energy liberated will go into heating up rocks underground. In order to try to make the process a bit more efficient water is usually injected along with the air/oxygen. When it comes in contact with the superheated rock some of that heat can be used to split the water (H20) into hydrogen and oxygen. The oxygen will burn with more of the coal and the hydrogen will come to the surface along with the carbon monoxide where it can be burned. Additional reactions between the hydrogen and coal can also produce methane. This mixture of carbon monoxide, hydrogen and methane is usually referred to as syngas (as opposed to natural gas) and is quite similar to the town gas that was made from coal during the 19th and much of the 20th century. This method somewhat increases the efficiency of the process but even so around 25-40 percent of the energy embodied in the coal is lost during the gasification process. This obviously has huge effects on the quantity of carbon emissions relative to the amount of useful energy generated which we will come back to later.

Schematic of the UCG process, using the linked vertical well (LVW) configuration

There are a two principle well configurations used to burn the coal underground. Both require at least two wells, one to inject the air and one to pipe the raw syngas to the surface. The simpler LVW (linked vertical wells) is simply two vertical wells linked together by some means. There are various methods that can be used to link the wells including hydraulic fracturing, reverse combustion, electrical-linkage and horizontal drilling. LVW only allows gasification of the coal in the region between the two wells and so requires many pairs of wells to be drilled to gasify large amounts of coal. If the seam is close to the surface, the cost of drilling all these wells may not be prohibitive but for deeper seams the LVW method is not likely to be used. The LVW has historically been widely used in UCG tests but appears to be falling out of favour compared to more complex techniques, especially when targeting deeper coal seams.

An alternative well configuration called CRIP (controlled retracting injection point) is the main method that is being considered at present. Developed by Lawrence Livermore National Laboratory (LLNL) in the 1970s, the CRIP method involves drilling one (or in some cases two parallel) horizontal well(s) through the coal seam. In the case of a single horizontal well, a vertical production well to take the syngas to the surface. For two parallel wells (usually around 30m apart) one would be used as the injection well and the other as the production well. In either case injection would start at the far end of the horizontal well and the injection point would be retracted along the well as the burn proceeds. A series of cavities will be burned out of the coal along the length of the injection well. This allows a considerably larger amount of coal to be burned using a single pair of wells.

Schematic of the UCG process, using the controlled retracting injection point (CRIP) method

There are a number of huge issues that have come to light during the limited testing of UCG over the last century and doubtless others that wait to be discovered if it is ever used on a large scale. The most serious known local issues relate to the wide variety of toxic hydrocarbon compounds that are produced as a by product of the process (particularly in lower temperature parts of the burn chamber). Of particular concern are BTEX (benzene, toluene, ethyl-benzene and zylenes) compounds, phenols and polycyclic aromatic hydrocarbons (PAHs). In particular the American Petroleum Institute, a body not know for its concern for human health, has stated that “it is generally considered that the only absolutely safe concentration for benzene is zero”. In fact there is already plenty of experience of the hazards of coal gasification. The production of town gas (during the 19th and 20th centuries) from mined coal in plants around the world has resulted in a legacy of contaminated sites. The big difference with UCG is that it is not happening is a sealed chamber but out in the natural environment, which pretty much guarantees that some of those contaminants will find there way into the biosphere.

The example of the contamination left by the gas works used for the production of town gas in the 19th and 20th centuries is instructive. Throughout the majority of this period most gas used for lighting and heating was manufactured in local gasworks by heating coal in retorts to produce gas and coke. This has left a legacy of sites highly contaminated with a variety of toxic and carcinogenic chemicals which can slowly leach into the wider environment or suddenly be mobilised by building works or attempted clean up operations. For instance in the 1985 case of Taylorville, Illinois it was discovered that land next to a public park was contaminated due to a coal gasification facility abandoned in the 1930s. The poor cleanup operation resulted in the mobilisation of contaminants and soon afterwards seven children in the town were diagnosed with neuroblastoma, a rare nervous system cancer. Government and industry attempts to cover up the cancer cluster eventually lead to a series of court cases.

Drawing of the “hell on earth” that was the interior of South Lambeth Gas Works in the 19th Century

However in addition to the example of old gasworks sites there is also numerous examples of contamination from the sporadic testing of UCG that has taken place since the 1930s. In both the Soviet Union and the United States experimentation with UCG gas resulted in significant contamination of groundwater with toxic chemicals. In particular the series of trials carried out at Hoe Creek, Wyoming in the 1970s documented serious environmental issues with a 1993 Department of Energy report concluding that “groundwater contamination posed a significant potential risk to humans and livestock”. The maximum recorded benzene concentrations in groundwater after one US trial was more than 4000 times the current UK “supposedly” safe threshold. The UCG trials carried out in the UK at Bayton, near Cleobury Mortimer in Worcestershire during the 1950s which were later abandoned resulted in questions being raised in Parliament about environmental issues.

A particularly pertinent example of contamination of groundwater by UCG can be found in Australia’s recent experiences with UCG tests. In the last decade three separate test sites have been operated in Queensland, these being the Cougar Energy plant near Kingaroy, the Carbon Energy plant at Bloodwood Creek and the Linc Energy plant near Chinchilla. Of these three plants, two have suffered significant problems. The Carbon Energy plant at Bloodwood Creek was shutdown in 2010 by regulators due to a number of environmental concerns. The most high profile recent failure of UCG has been the Cougar Energy plant at Kingaroy which operated for 5 days in 2010 and resulted in the contamination of groundwater with benzene and toluene and in the fat of cattle grazing nearby. Cougar Energy has since been ordered to dismantle the plant. It is notable that in both the Cougar and Carbon Energy incidents the companies tried to coverup the problems. In the light of this the so far clean record of Linc Energy in Australia does not inspire much confidence.

Another illustration of the insanity of UCG can be seen by looking at what happens when coal seams are accidentally set on fire. A particularly well documented example is that of the ex-town of Centralia in Pennsylvania. In around 1962 a coal seam below the town was set alight. For the first 10-15 years no one really noticed any major effects and eight separate attempts to extinguish the fire proved unsuccessful. However by the beginning of the 1980s the effects of this creeping menace were starting to be felt. Pavements began to crack, trees started dying and people passed out in their homes from toxic fumes. The problems escalated and after a hole opened up in the ground swallowing a child who was only just pulled to safety. It was realised that there was a serious problem. By 1990 the population of over a thousand had dropped to 63 with most homes having been condemned and demolished. In 2002 Centralia’s postal code was eliminated by the US Postal Service and today the area is a wasteland. The fire is expected to keep burning for at least 250 years. While most of the coal seams targeted by UCG are likely to be deeper than those under Centralia it clearly demonstrates that the idea that this sort of process can be completely controlled is a complete fantasy.

Centralia, Pennsylvania abandoned due to a coal fire burning underneath the town for the last 50 years

While the catalogue of local(ish) environmental contamination issues that surround UCG are very scary, the potential global climate impact of the technology is positively nightmarish. Due to the inefficiencies associated with UCG the carbon emissions per amount of useful energy produced are even higher than for conventional coal. Worse, the amount of extra coal that UCG might make available for combustion has been estimated to be 4 trillion tonnes worldwide. If this was all burned it would emit around 15 trillion tonnes of carbon dioxide into the atmosphere which would raise the carbon dioxide concentration in the atmosphere by about 2000 ppm. Since the present carbon dioxide concentration in the atmosphere is around 390 ppm (compared to the pre-industrial value of 280 pmm) and it is generally accepted that going above a value of 450 ppm would be likely to have catastrophic consequences (while many people advocate a reduction to 350 ppm as a safe course of action) an addition of 2000 ppm would be entirely suicidal. Also the syngas produced by UCG contains a significant amount of methane (around 15 percent) and if the amount of fugitive emissions (leaking of the gas directly into the atmosphere before it is burned) for UCG turns out to be similar to other unconventional gas extraction methods then this will only intensify the impact (since methane is a much stronger greenhouse gas than carbon dioxide).

All this might lead a rational observer to conclude that no one could possibly be stupid enough to want to try to develop UCG in Britain but this would be a far too optimistic view of the levels of greed and stupidity amongst those in positions of power. In fact the government has been aggressively pushing UCG for at least the last 10 years and the recent huge increases in energy prices have piqued commercial interest. So far 24 UCG licences have been sold to a variety of startup companies created to develop the technology (for some of the licenced locations see the black outlined regions on the map on the locations page). In order to try to limit initial opposition all these first UCG licenses are for areas just off the coast, but close enough that the horizontal wells can be drilled from the shore. This, it is argued, will mean that fresh drinking water cannot be contaminated but even if this was true, why contaminating the sea is okay is never mentioned. Several of these licences are right next to major population centres, such as Edinburgh, Newcastle and Swansea. Previous tests have only occurred in low population density areas (usually deserts) so this will be something of an experiment. The most advanced project in Britain appears to in Swansea Bay where Clean Coal Ltd is poised to begin testing this year but other projects around the UK are probably not too far behind. The dawn of a future that is well worth resisting.