Digging deep: Will Underground Coal Gasification halt the energy crisis?

underground coal gasification

In the words of Jamiroquai, we’re “going deeper underground”. That’s with regards to harnessing energy from coal that is. And it’s via a process called underground coal gasification or UCG for short.

First explored by the Soviets in the 1930s, UCG is a process which involves drilling two boreholes into the coal seam, one for oxygen and water/steam and the other to extract the resulting gas to the surface.

From what I’ve worked out, it works a bit like this: the coal is set on fire far beneath the surface and is then kept burning by oxygen being pumped down into the rock. The combustion that results from the high temperatures, oxygen and water/steam turns much of the coal into gas. As well as the gas that can be used for household consumption called syngas, carbon dioxide is produced along with hydrogen, carbon monoxide, methane and sulphur oxides. The diagram below, taken from the British Geological Survey, illustrates this.

So why is UCG making a comeback? It’s not as if it’s something new; it’s been around for decades and many countries including China, Australia and America are already doing it. China has by far the most plants with at least 30 operating throughout the country.

So why are we looking to UCG now? What’s changed?

Traditional coal reserves are depleting at an ever increasing rate with the rise of emerging economies, so countries are looking at new ways, especially those that are cheap, to meet energy demands.
Higher oil and gas prices mean that there is now value in extracting energy from the coal seams. Previously, the UCG process was deemed too expensive in relation to the value of energy generated. Now it offers a more competitive alternative to oil and gas.
New drilling technology from oil and gas has made the UCG process easier and more commercially viable.
The UK has large reserves of coal off the North Sea coast. These could be used to reduce our dependence on imported gas and oil thus securing, in part, our future supply of energy.
We now have to meet EU emissions targets so anything that lessens our reliance on traditional coal, oil and gas is welcome.
UGC is a cheaper and more reliable source of ‘clean’ energy than many renewables which are still yet to achieve real economies of scale due to limited implementation.

Price competitiveness would seem to be the largest factor in play as to why UCG is being so actively encouraged by so many countries. Below is a graph depicting the cost of UCG for power generation against other alternatives (source: UCG association):

The UK government is keen to use UCG. 18 licenses have so far been granted to companies to conduct UCG tests. But what does this mean for us? Let’s take a look…

Below are a few advantages for using UCG:

The financials. It’s cheaper than many alternative energy sources on the market and is even said to rival nuclear in terms of emissions and plant running costs.
UCG is said to be a ‘clean’ source of energy production as the gas produced can be processed of all the carbon dioxide before it reaches its destination with end consumers. Carbon capture and storage technology (CCS), involves the storage of carbon dioxide by injecting it back into permeable rock on the plants site where the coal once was.
Is doesn’t require anyone to go below the ground. With high profile mine collapses like those in Chile and Swansea in recent years, UCG is deemed safer by many.
Syngas can be piped direct to the end consumer. So this could reduce environmental impacts of using roads for transportation which is currently required for some forms of fuel.
The ash content in UCG is less than those produced from traditional coal mining.
Some of the poorest nations have low quality surface level mines, so UCG offers new possibilities for achieving energy generation from their own natural resources.

And here are the concerns that have been raised about UCG:

There is mounting concern that if the UCG process was widely adopted and the estimated additional 4 trillion tonnes of coal was burned without using carbon capture technology, carbon dioxide levels in the atmosphere could quadruple.
With any CCS strategy there is the question as to whether the cavity left by the burnt coal will be large enough to hold all the carbon dioxide produced. It is also not clear as to whether any and all leakages could be prevented and over what period of time this could be done.
CCS requires additional funds. Some are worried that companies in emerging countries will forego this expense in pursuit of higher profits and that corruption in local and national governments will allow them to get away with it.
There is some fear that the water table could become contaminated. After gasification has occurred, the toxic and very water soluble chemical phenol remains in the ground. Highly reactive, it can cause benzene to leak into the groundwater. Recovery time is estimated at two years should this happen – much less than an equivalent underground oil leakage.
It’s been suggested that once the coal has been used, the land could collapse in. However, according to Julio Friedman of Lawrence Livermore National Laboratory, if the site is chosen correctly this is of little risk.
Tests can’t be carried out in labs but large scale pilot tests cost a lot of money. The EU has, however, provided grants to help towards these development costs.
Underground gasifiers are more difficult to control than those used in traditional mining. In UCG, only estimates have to be made for variables such as distribution of reactants in the area and water influx.

Should we be welcoming UCG to the UK with open arms?

What seems to be clear is that an effective carbon capture & storage plan needs to be in place if we are to obtain energy through UCG without further contributing to climate change. Cost-effective management of carbon dioxide needs to be dealt with if UCG is to be successful in dealing with its many stakeholders’ wants and needs.

With the rest of the world adopting UCG at an increasing pace, it is surely in the UK’s interest to at least plough some money into getting a few projects off the ground. We’ll know more about their viability from actually building and operating some initial sites including the effectiveness of capturing the CO₂.

There are some questions however as to whether investment might move away from renewables and into UCG if it proves to be more commercially lucrative and, while it could be a good source of ‘clean’ energy, I believe that renewable power generation is a better long term investment with fewer potential drawbacks.

As for the UK’s role in coal gasification worldwide, it should be the flag bearer for best practice and should ensure that all countries generating power this way actively invest in the carbon capture technologies required to make it a clean fuel. We cannot allow emerging countries to avoid this expense at the cost of damaging the environment and if we have to transfer technology then we should do so.

I would really like to hear your thoughts on UCG and whether you think it’s a good way of producing affordable energy. It could eventually mean reduced utility bills for all of us. Let me know your comments below or follow me on Facebook or Twitter if you found this interesting.