MIT unlocking carbon capture and storage

Research shows CO2 capture is affordable today at coal-fired power plants and provides a framework for estimating the storage capacity for greenhouse gases underground.

Researchers at the Massachusetts Institute of Technology released two studies today that could speed the adoption of carbon capture and sequestration projects.

The findings provided interim steps to get carbon capture and storage (CCS) projects adopted, showing that partial capture can be economical and that more research is needed into capillary trapping coefficients, researchers said.

The authors plan to present their work Tuesday at the Ninth International Conference on Greenhouse Gas Control Technologies in Washington, D.C.

"We want to expedite large-scale adoption of carbon capture and storage technology, but what it really comes down to is whether anyone can afford it," said Ashleigh Hildebrand, a co-author of one of the studies and a graduate student in MIT’s chemical engineering and technology and policy programs. "Our research is aimed at reducing the uncertainty."

Carbon capture can increase the initial capital cost of a coal-fired power plant by 30 percent to 60 percent and decrease plant efficiency. Additionally, CCS hasn’t been proven at full scale, MIT says.

Hildebrand’s study, co-authored with Howard Herzog, principal research engineer at the MIT Energy Initiative, showed that today’s coal-fired power plants could use CCS projects for 60 percent of their emissions to optimize economies of scale. Additional carbon capture would require significant additional capital investments, the MIT analysis shows.

"We’re talking about this for the first wave of CCS," Hildebrand told the Cleantech Group. "Obviously the long term goal is widespread development of full capture plants. These results indicate that it is possible to achieve partial capture, so utilities might actually be able to afford it in the interim until the technology advances."

That means coal-fired power plants—the least costly method for producing energy—could meet the world’s increasing electricity demands while producing the equivalent emissions levels of natural gas power plants, Hildebrand said.

The study focused on the construction of new coal-fired plants, which are facing regulatory and financial hurdles because of the presumption that a carbon tax could make the plants too expensive to operate. Hildebrand said the findings are also applicable to existing coal plants.

"The sooner we can get out the first wave of CCS plants using full capture or partial capture, the sooner we can generate a lot of technical and operating knowledge that provide a source of CO2 to investigate the sequestration side as well," she said.

The second study from MIT developed a mathematical formula to estimate the underground storage capacity in geological basins for carbon sequestered from power plants. The MIT model also estimates how much CO2 will migrate from its injection well and predicts the likely path through underground slopes and groundwater.

Ruben Juanes, co-author and the ARCO professor in energy studies at MIT, said two key factors can determine the distribution patterns and possible leakage of sequestered carbon: depth (which determines pressure and temperature) and the capillary trapping coefficient, a factor that had not previously been considered in studies looking at sequestration capacity of underground basins.

The capillary trapping coefficient looks at how the sequestered carbon interacts with fluid and rock. The Earth’s pressure liquefies CO2, which is dispersed throughout the basin’s structural pores and eventually dissolves and reacts with reservoir rocks to precipitate out into harmless carbonate minerals, MIT says.

"It’s a crucial parameter, but we know very little about it," Juanes said. "It’s an inexpensive parameter to obtain, but laboratory studies need to be done. That’s one of the key findings here."

The formula—which Juanes and co-author Michael Szulczewski, a graduate student, expect to publish soon—could be used by policy makers and regulators to evaluate the potential of certain geographical areas to hold CO2 and calculate sequestered carbon.

The model has shown that the Fox Hills Sandstone in the Powder River basin between Montana and Wyoming would hold around 5 gigatons of CO2—more than half of all the CO2 emitted by the United States each year. The researchers plan to apply the model to regions outside the U.S. soon.

Future research will study the geo-mechanical effects that take place upon the injection of CO2, he said.

Juanes noted that the study has not yet been validated and provides only an estimate for capacity, although the estimate is likely to be more exact than what exists currently.

"Getting capacity estimates is one of those early, early data points one needs to decide if this sequestration technology has a place or not," he said.

Pilot projects have sequestered small amounts of CO2 in places such as Norway, Algeria and Texas. In June, the U.S. Department of Energy announced plans to invest $1.3 billion in multiple commercial-scale CCS projects as part of the FutureGen program (see U.S. DOE puts out the call for new CCS projects).

Researchers across the globe are trying out different techniques to sequester and remove carbon emissions. In February, researchers at the University of California, Los Angeles, said they found a way to filter greenhouse gases from power plants by using creating crystal structures that can selectively capture carbon dioxide (see Carbon capture gets crystal powered).

A government-backed project in Canada by Houston-based Spectra Energy said in May it was researching whether deep underground saline reservoirs were appropriate for carbon capture and storage (see Spectra Energy looking at carbon capture in Canada).

And some companies, such as Halifax, Nova Scotia-based Carbon Sense Solutions and Los Gatos, Calif.-based Calera, are developing methods to convert carbon into a material that can be used to make concrete (see Capturing carbon with concrete).

By Emma Ritch, Cleantech Group

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