If averting climate disaster really does demand that 80% of the world’s coal reserves are left in the ground – along with half the natural gas and a third of the oil – as a recent study from University College London concluded, then the future of coal power has never looked less certain.
With traditional coal generation increasingly recognised as unsustainable, and with the call to abandon fossil fuels growing by the day, it seems that the industry faces further hard times ahead – unless it can re-invent itself and finally turn the much-heralded potential of ‘clean coal’ into a reality.
Integrated gasification combined cycle (IGCC) technology – a modern take on the process that provided ‘town gas’ to light 19th century streets – is arguably the main contender to achieve this, and its appeal is clear: coal is made to yield a clean-burning, synthetic gas (syngas), which is stripped of pollutants and impurities and then burnt to produce power, with heat recovery providing steam to produce more electricity, and hence greater efficiency.
21st century coal
Perhaps not quite the holy grail, but for utilities like Southern Company subsidiary Mississippi Power – the builders of the new 582MW Kemper County energy facility near DeKalb, Mississippi – it is an approach that promises a number of significant advantages.
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The plant is billed as a coal generation plant for the 21st century, and, once completed, it will use advanced IGCC technology, the first of its kind. The technology will convert locally-mined lignite into syngas to generate electricity cleanly and efficiently, while capturing an estimated 65% of the CO2 produced.
Nevertheless, opponents point to the questionable economics of IGCC plants, with their high capital costs driving estimates ranging from around $1,500/kW installed capacity to well over twice as much – and certainly considerably higher than a comparable conventional pulverised coal (PC) facility.
"Whether or not the financial perspective of coal includes all the externalized costs or not, IGCC is comparatively more expensive per kilowatt hour of electricity generated than other sources of energy," says Kyle Ash, senior legislative representative for Greenpeace USA. "IGCC is just bad economics."
That may not always remain the case, however, as the technology matures, particularly if the proposed regulations on emissions come into place. According to a spokesperson for the US Department of Energy (DOE) owned and operated National Energy Technology Laboratory (NETL), "Under such a scenario, the cost gap between IGCC and PC plants may be reduced as capture of CO2 is generally less costly and has a lower energy demand for an IGCC relative to a PC."
There is another financial upside to IGCC with carbon capture, particularly when, as in the case of the Kemper County plant, the facility is being constructed adjacent to a lifetime’s supply of coal, and near a CO2 pipeline, which simplifies the reuse of the captured carbon for enhanced oil recovery. These new generation plants promise higher thermal efficiencies and lower costs as a result.
As Southern Company media relations spokesperson Jeannice Hall explains "customers will reap the benefits of the low-cost fuel source the first day it begins generating electricity fuelled by Mississippi lignite. Once the project begins operations, the sale of captured carbon dioxide and other marketable products of the coal gasification process is expected to generate at least $50m annually."
It goes some way to help bolster the environmental case, too.
Environmental ups and downs
In addition to the carbon capture and storage (CCS), supporters argue that taking away emission-forming contaminants before burning the syngas significantly cuts air pollution, notably reducing sulphur dioxide, NOx, mercury and particulate emissions.
IGCC plants also use an estimated third less water than equivalent-sized conventional facilities – and this could be important if water availability issues continue to grow in the future. According to Timothy Diehl, USGS hydrologist and co-author of ‘Withdrawal and Consumption of Water by Thermoelectric Power Plants in the United States, 2010’, the general trend is for water consumption to increase in broad proportion with the power being generated, so more water-efficient power stations bring obvious benefits.
While IGCC plants may use less water, environmentalists point out that the technology has a poor reputation when it comes to keeping that water clean. The DOE’s report into its own Wabash River pilot plant – which was the first of the DOE Clean Coal Technology programme’s IGCC projects to achieve commercial operation in the 1990s – noted that selenium and cyanide discharge limits were "routinely exceeded."
The idea of CCS too – dubbed the ‘carbon capture scam’ by Greenpeace USA – has also come in for criticism, not least because by being used to enhance oil recovery it represents what Ash has called a catalyst for even more CO2 pollution. He writes in his blog that "the CO2 from burning coal ultimately still gets into the atmosphere, but expensive, subsidized equipment first takes the CO2 on a long, inefficient detour."
Last chance for coal?
So where does this leave IGCC? Is it, as some have suggested, the ‘last chance for coal’, a valuable solution to future energy needs or an unwelcome distraction along the way to leaving the world’s remaining reserves in the ground to avert global catastrophe?
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"It is good to think of coal in terms of its last chances, since truly its days are numbered as an energy source," says Ash. "One big problem with IGCC is it requires massive new capital investment in coal-dependent infrastructure, and it makes little sense to put that money into something that we must stop using decades before its end of life. Climate science demands we phase out the use of fossil fuels as soon as possible."
Southern Company, however, believes that America’s most abundant fuel source, coal, must continue to be a component of the full portfolio of energy resources, and views novel technology development as a key means to meeting the future power demands of America and the world. Having developed the Transport Integrated Gasification (TRIG) technology to be used at Kemper with KBR, they are now marketing it across the globe in an attempt to help utilities meet growing consumer need while reducing emissions.
"Due to growing demand and high natural gas prices, China, India and other parts of Asia are expected to add more than 400,000 megawatts of new coal-based generation by 2035. Energy companies in those regions can benefit from the use of low-rank coal, which constitutes half of the world’s existing coal reserves and is particularly suited to the application of TRIG," Hall says.
According to NETL, for gasification to achieve widespread market penetration, technology improvements will be required to reduce capital and operating costs relative to competing technologies – but few question that such improvements can be made in time. Ultimately, however, whether IGCC really is the future of coal power may not be about the technology at all. It could all come down to a much bigger question, and one that has huge ramifications for the whole of our energy supply for generations to come.
Should we just leave it all in the ground?