The clean coal triad

August 28, 2012

Despite being the dirtiest fossil fuel, coal continues to be the world’s primary source of energy.  Although developed nations have slowed their use of coal, it is the fuel of choice in developing nations because it is so cheap and abundant.  Indeed, even in advanced nations, coal consumption has begun to increase again due to a variety of factors.   But, even as modern coal burning plants in advanced nations become more and more efficient, they still emit vast amounts of CO2.

Coal, even though it is a major contributor to global warming (and, if untreated, a source of even worse pollutants as well) will be a primary energy source for most if not all of the 21st century.   Energy is required not just to modernize the developing world, but to feed their growing populations, and that energy will come from fossil fuels in general and from coal in particular.   The policy question is not how to stop the use of coal, but how to clean it up.

coal pollution in Datong, Shanxi Province, China

Richard K. Morse is the Director of Research on Coal and Carbon Markets at Stanford University’s Program on Energy and Sustainable Development.  He addresses the problem of coal (we need it but we can’t use it) in the most recent issue of Foreign Affairs.   Morse believes that, essentially, the world can have its cake and eat it, too:

Given how dominant coal is, one of the most promising ways to fight global warming is to make it emit less carbon dioxide, a solution that is less elusive than commonly thought. Merely installing the best available technologies in coal plants in the developing world could slash the volume of carbon dioxide released by billions of tons per year, doing more to reduce emissions on an annual basis than all the world’s wind, solar, and geothermal power combined do today. And advanced technologies now in the works could someday allow coal to be burned without releasing any carbon dioxide into the atmosphere.

Morse focuses on two approaches.  The first is carbon capture and sequestration (CCS), which I have discussed several times on this blog.  CCS processes trap the CO2 that is emitted when coal is burned and stores it safely underground so that it cannot enter the atmosphere and contribute to global warming.   CCS, Morse acknowledges, is currently too expensive to be carried out on anything but a demonstration level, but he believes that increased research funding, proper regulatory changes, and coordination between countries could bring the cost down.

How CCS works

The second approach that Morse discusses is underground coal gasification (UCG), an even more esoteric technology than CCS.  As Morse notes, UCG

involves igniting coal seams deep below the earth’s surface, which transforms them into a gas that can then be piped aboveground to fuel electrical generators or create diesel substitutes. The technology is experiencing a wave of new investment thanks to new advances in drilling and computer modeling that are bringing down costs. UCG leaves most of the pollution associated with burning coal belowground, especially when the process is combined with CCS.

It seems to me that the CO2 reduction involved in UCG is a side benefit, not a main selling point.  The primary value of UCG is that is allows access to extremely deep seams of coal that could not otherwise be mined.  Here is a diagram of the UCG process from the UCG Association:

How underground coal gasification works

Both of these approaches involve treating CO2 primarily as a waste product to be disposed of (although, Morse does mention the potential for injecting captured CO2 into old oil wells to enhance recovery of remaining reserves while at the same time sequestering the gas deep in the wells).  However, there is a third approach that should be combined with these two – carbon capture and utilization (CCU), of which the most promising aspect is converting the excess CO2 into other chemicals, such as methanol for use as a clean burning fuel.   This approach both scrubs CO2 from the process, but extends the value of coal by turning it into a dual purpose agent.  This is the theory behind the Methanol Economy argument.

The coal gasificatioin process

So, this is the clean coal triad – CCS, UCG, and CCU.  Together, they lead to a cleaner environment without sacrificing the energy needs of a world growing not just in population, but in technological sophistication.  It won’t be cheap or easy to build this kind of economy, but it is a very clear path forward.  This is the essence of technological positivism – the twin crises of energy supply and global warming are technological problems demanding technological, not political, solutions.  Politics of course will have its place – we need to create a regulatory regime that at once allows this approach to flourish while at the same time protecting the environment.  But, make no mistake, the solutions are coming from the engineers, not the politicians.


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