Myths and realities about carbon storage

Leave the coal deep underground, they say, and forget the death and expense that come with mining. Instead, put a drilling hat on.

By baking coal buried thousands of feet underground using controlled fires and gravitys pressure, they say, previously inaccessible seams can be shifted into easily extracted gas. The gas, pumped up, will fuel turbines. And when most of the coal is gone, inject carbon dioxide to fill the void.

It is a simple concept that could reduce construction costs and eliminate the need to build the extensive pipelines required for CO2 storage at any large scale, said Tomas FernandezSteeger, an assistant professor at Aachen Universitys Department of Engineering Geology and Hydrogeology. We make space, he said, before we put something in the space.

The model combines an environmentally problematic but proven technology, underground coal gasification, with recent experiments finding coal seams greedy to trap CO2 but lacking in storage. By filling the hollows created by underground burning with waste CO2, companies could potentially create coalfired power plants for the same price as current carbonspewing power stations.

The Aachen project is still theoretical. But it is part of a new wave of startup companies and scientists who have targeted underground coal gasification UCG, a centuryold idea, as the budgetminded savior to curbing greenhouse gas emissions.

In one stroke, advocates say, underground gasification could triple U.S. coal reserves put an end to dangerous underground and environmentally degrading surface mining and provide an affordable way to collect CO2 emissions for storage. And it can be done without the technical mishaps and water contamination that have plagued past efforts.

The reality is that coal use in the developing world will double over the next few decades, and with its low costs, UCG holds more promise for reducing emissions than nearly any other option, said John Thompson, director of the coal transition program at the Clean Air Task Force, a nonprofit focused on reducing atmospheric pollution.

Its a breakthrough on cost with carbon capture and storage, Thompson said.

One recent estimate has placed the cost of UCG plants with CO2 storage as equal to those of surface coalfired plants without any capture technology. Other estimates have found the synthetic gas UCG produces cheaper than natural gas, even at current depressed levels.

Simply put, it is coal energy with a natural gas footprint, said Julio Friedmann, leader of the carbon management program at the U.S. Energy Departments Lawrence Livermore National Lab.

China, which has had several recent mining tragedies, has embraced underground gasification. There, it is known as coal without mining, Thompson said.

One largescale project is producing synthetic gas out of Inner Mongolias coal seams. Australia is also operating a large UCG pilot, and more projects are in the pipeline in Asia. Fitfully, UCG is also returning to the United States, where it was intensely studied after the 1970s oil crisis. An Alaskan company, CIRI, has begun the process of building a 100megawatt UCG plant in the Cook Inlet. The proposal, which would use its CO2 for enhanced oil recovery, is undergoing environmental review.

UCGs profile, should the first projects go smoothly, will rise soon, Thompson said. If you couple [UCG] with CCS, it is a very, very attractive way of getting energy out of coal, he said, while also allowing the world to make deep, deep reductions in CO2 by the midcentury.