Plans are moving forward in the United States and abroad for the first demonstrations of methods to capture carbon-dioxide emissions from burning coal and store this greenhouse gas in underground geologic formations. But can the process work as advertised?
One reason for the interest in what's called carbon capture and storage is that coal ranks as the world's biggest source of greenhouse emissions, at 40 percent. The International Energy Agency has warned that global carbon emissions must stop rising before 2020 for the world to avoid dangerous climate change.
But coal is the energy mainstay, accounting for roughly half of U.S. electricity production and an even greater share of power in emerging economies such as those in China and India. Developing countries are opening up two new coal-fired power plants each week.
Unless a realistic alternative can be found to venting coal emissions directly into the atmosphere, countries simply may have to begin meeting their energy needs in other ways. Rather than shut down coal plants, countries are pinning their hopes on carbon capture and storage. Recently, U.S. Energy Secretary Steven Chu said that the process must be ready for global use within 10 years.
The question is whether carbon capture and storage can be made safe and practical. If it turns out to be the wrong choice, we will wind up with many more coal plants in the world without any way to capture the emissions -- and this, in turn, could have dire environmental consequences.
It is critical that we make aggressive use of conservation and alternative-energy sources to cut coal emissions right now rather than wait to see if a hypothetical system will work. The fact that many energy experts are skeptical about the viability of carbon capture and storage does not inspire confidence; rather, it generates further skepticism.
Consider some of the critical issues facing carbon capture-and-storage:
The plan is to inject millions of tons of compressed carbon dioxide into saline aquifers deep underground. In theory, the carbon dioxide would be sealed in by thick layers of rock, where it would remain undisturbed for centuries. But should the carbon dioxide mix with water underground and form carbonic acid, it could leach poisonous materials from rock that could then seep out.
If carbon dioxide escaped from an injection site, it could trigger explosions or asphyxiation from poisonous gas. A naturally occurring release of carbon dioxide from a Cameroon lake in 1986 killed hundreds of people. Though that release was from nature, grass-roots protesters in Germany have been citing it as part of a well-coordinated campaign to prevent carbon capture and storage.
There is current research to produce a solid waste such as calcium carbonate instead of carbon dioxide. This would result in many more waste storage options, although it could lead to further delays and added costs.
Currently, there is no proven technology for capturing carbon dioxide at coal plants. Various chemical solvents are being tested, but getting electric utilities, let alone other countries, to agree on a process, is likely to be many years off.
Moreover, carbon storage, which is also known as sequestration, has never been demonstrated at industrial scale. Pipelines would be needed to transport the carbon dioxide to injection sites. A study conducted by the National Petroleum Council determined that sequestering a billion tons of carbon dioxide from coal burning each year in the United States would entail pumping about 50 million barrels per day of liquefied carbon dioxide into saline aquifers. That amounts to 2.5 times the volume of oil handled daily in the United States.
It's estimated that electricity produced at a coal plant with carbon capture and storage would be at least a third more expensive than from a power plant without such a system. The National Mining Association estimates that the cost of capture and storage deployed nationally would reach $1 trillion.
Considering local opposition in this country to large infrastructure improvements of just about any kind, public acceptance could be a problem. Even renewable-energy projects such as wind turbines and solar arrays have been thwarted by not-in-my-backyard opposition. That alone is no reason to abandon a project, but it emphasizes that the political as well as technological challenges facing carbon capture and storage may be daunting.
For the near term, using natural gas instead of coal is the most cost-effective way to reduce carbon-dioxide emissions. But this is no long-term solution since there is still plenty of carbon dioxide emitted from natural gas and the price of electricity from natural gas is unpredictable.
For the longer term, greenhouse-gas emissions can be reduced significantly through the increased use of carbon-free nuclear power. Though nuclear plants cost a lot to build, the electricity price is likely to be less than electricity produced by fossil fuels with carbon sequestration, or even with reasonable cap-and-trade charges for carbon emission. And unlike solar and wind energy, nuclear plants generate large amounts of power around the clock, regardless of weather conditions. We also know that used nuclear fuel can be reprocessed to produce more fuel for electricity production or, alternatively, stored safely above ground in concrete-and-steel casks for at least 300 years.
But nuclear power alone is not enough. The use of renewables must play a part, and increased energy efficiency is critical. If we hope to reduce greenhouse emissions 80 percent by 2050, the goal of current legislative efforts in Congress, there will need to be aggressive energy-efficiency improvements.
California has taken the lead by decoupling electricity rates from energy production. The Public Utility Commission sets targets for electricity sales by the utilities, which then split the savings with customers when energy use falls below state targets. This encourages conservation and efficiency instead of giving utilities the incentive to increase income by selling more electricity.
The average Californian uses about 40 percent less electricity per year than the average American. Other state utility commissions should reward utilities for fostering energy conservation. And policy makers across the country should look askance at carbon capture and storage as a way to keep burning coal and instead encourage alternative sources of energy and energy efficiency.
Edward H. Klevans is professor and department head emeritus of the Department of Nuclear Engineering at Penn State University ( email@example.com ).