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Voices: Must we capture and store carbon from coal to meet emission-reduction targets?

More than half the electricity in the United States comes from coal-fired power plants.

Credit: 

iStockphoto.com/Vera Tomankova

Last Wednesday, Sens. John Kerry and Joe Lieberman unveiled a comprehensive energy bill (PDF) called the American Power Act. The central purpose of the proposed legislation (along with a similar bill passed by the House of Representatives in June 2009) is to significantly curb the nation’s carbon dioxide emissions.

The American Power Act (PDF) requires a 17 percent reduction by 2020, relative to 2005 levels, and an 80 percent reduction by 2050. This would happen in part through a carbon emissions trading system — called cap and trade — that is designed to discourage the use of carbon-based fuels over time by putting a price on carbon. At the same time, the legislation includes incentives and support for non-carbon-based energy solutions, including renewables (such as solar and wind power), efficiency and conservation programs, advanced fuels, and nuclear power generation.

Additionally, components of the legislation would reduce the emissions from our existing carbon-based energy infrastructure. One of those components, carbon capture and storage (CCS), aims to capture carbon dioxide emissions, primarily from coal-fired power plants, before they are released into the atmosphere and then sequester the carbon (e.g., by injecting it deep into the subsurface). There are numerous Web resources to learn more about the details of CCS technology — this page from the World Resources Institute is a great place to start.

Coal as an energy source is very significant worldwide. For example, in just the past decade, China’s coal consumption has increased by an order of magnitude compared to U.S. coal consumption (PDF from Energy Information Administration). And in the United States, burning coal currently accounts for nearly half of total electricity production. In the U.S., the carbon dioxide emitted into the atmosphere from coal-fired power plants accounts for a substantial portion (roughly 35 percent) of the nation’s total greenhouse gas emissions. Coal is a relatively abundant natural resource with long-established methods and infrastructure for energy extraction and production. In a global context, many analysts think coal will continue to be an important energy source for several more decades — even within a carbon-emissions-reduction framework.

There are a couple of ways being considered to achieve this carbon-emissions reduction required by bills such as the new American Power Act. First is significantly reducing our coal usage through large-scale efficiency improvements, such as Smart Grid technology or improving building design standards, while simultaneously moving toward using more renewable fuels. Second is to try to capture and store carbon before it is emitted into the atmosphere.

Regarding the first: Numerous industry analysts and independent researchers indicate that even with an aggressive plan to reduce emissions, coal is almost assuredly going to remain a large part of our energy mix for the near future. So yes, let’s try to move forward, but in the meantime, we have to find ways to reduce the carbon dioxide emissions from what is an inherently “dirty” process.

That brings us to the idea of “clean coal” — the coal industry’s marketing scheme for CCS technology, in which they claim that we can continue to use the same coal to generate electricity so long as we use CCS technology to reduce the emissions.

However, CCS is only feasible within the framework of an aggressive plan to reduce emissions — something the coal industry and advocates of clean coal discourage. The use of coal, even with advanced CCS technology, will never be “clean” in the way that this marketing campaign suggests. After all, the coal itself is not any cleaner — it’s the processing during energy extraction that reduces emissions. Another issue is that CCS may not be feasible technologically and it may be far too energy-intensive to make it worthwhile.

Given that we likely will not be able to reach emissions-reduction targets and meet predicted energy demands without CCS in the mix, we had better start investing in large-scale demonstration projects at the very least, as researchers like Pushker Kharecha and outspoken climate scientist James Hansen of the NASA Goddard Institute for Space Studies argue in a recent paper in Environmental Science & Technology.

It’s important to remember that applying CCS technology to existing coal-fired power plants is just one of a portfolio of solutions. But at the same time, those advocating the use of coal as an energy source should realize that technologies like CCS are designed as a bridge to a low-carbon future and are not meant to extend the use of coal indefinitely into the future.

Encouraging research, development and implementation of CCS technology while also reducing our dependence on coal-based electricity will be a challenging balancing act for policymakers. While these policy debates regarding if (or to what degree) CCS should be implemented continue, I think that we, as earth scientists, need to continue thinking about how we can utilize our expertise to help solve these problems. A lot of the research regarding the storage aspect of CCS will be conducted by geologists who characterize the deep subsurface or oceanic crust and geochemists who investigate reactions between injected carbon dioxide and potential reservoirs.

Brian Romans
Tuesday, May 18, 2010