For more than three decades, gasification technology has promised a smarter conversion of coal to electricity. By using heat and pressure to turn coal’s motley mix of molecules into a consistent stream of simple gases, gasification plants squeeze more power from a ton of coal and control the resulting by-products better. In April, engineers in Tianjin, China, fired up a gasification power plant that will provide a “critically important” test of the technology’s commercial potential as a low-carbon power source, according to Julio Friedmann, who leads the carbon management program at Lawrence Livermore National Laboratory, in California.
At 250 megawatts, the facility, known as GreenGen, is the world’s largest coal-fired integrated gasification combined cycle (IGCC) generator. It’s also the first built explicitly as a test bed for capturing carbon. This combination of carbon capture and commercial scale is needed to evaluate coal gasification’s potential contribution to stopping and reversing human-accelerated climate change. “We still have no plan as nations or as a world to make really deep greenhouse-gas emissions cuts. We have not economically vetted most of our important options, including IGCC plants such as GreenGen,” says Friedmann.
GreenGen more closely resembles a refinery than a generating station. IGCC plants turn coal into a blend of gases before burning those gases to drive both gas and steam turbines. Unlike all IGCC plants that preceded it, GreenGen is designed to support an additional process whereby its carbon waste is extracted before combustion. Gases from the gasifier react with steam to produce hydrogen to fire the plant’s turbines and a pure stream of carbon dioxide that is far easier to capture than the diffuse CO2 in a conventional power plant’s flue gases.
GreenGen and the handful of other IGCC coal plants in various stages of construction worldwide—including another plant in China and two in the United States—are the sole survivors among dozens of IGCC projects proposed and shelved over the past decade. Most fell by the wayside only in the past few years. A push for carbon legislation in the United States collapsed, as did the 2009 climate treaty negotiations held in Copenhagen. Without such measures, utilities have no incentive to invest in carbon capture. Over the same period, coal progressively lost its status as the cheapest fuel for power generation, as hydraulic fracturing operations flooded the natural gas market and slashed gas prices.
The resulting IGCC casualties include even FutureGen, the flagship project in the U.S. Department of Energy’s Clean Coal program and the inspiration for GreenGen. The Bush administration killed FutureGen in 2008 amid rising costs. The project may return under President Obama but as a test of a simpler but even less-proven low-carbon coal scheme known as oxyfuel combustion.