A pollution-free coal plant?

A power plant that gasifies coal, produces hydrogen, and seguesters carbon is the DOES answer to the question, "How will the U.S. reduce its greenhouse gas emissions without signing the Kyoto Protocol?" But unproven technologies, an aggressive schedule, and the energy industry's historical inability to cost-share raise questions about the program. Is this just another pie-in-the-sky federal boondoggle or the coal-fired plant of the future?

By Dr. Robert Peltier PE, Editor-in-Chief POWER

This February, the U.S. Department of Energy (DOE) announced a 10-year, $1-billion, public/private project to engineer, build, and operate a 275-MW power plant that it calls "FutureGen" but that is designated the "Integrated Sequestration and Hydrogen Research Initiative" in the DOE's budget (Figure 1). FutureGen is a variation on the DOE's old "Vision 21" zero-emission, coal-fired power plant, with coal gasification added at the front end. The new wrinkle is that the coal gas is not burned but is separated into hydrogen and carbon dioxide, making CO2 capture much easier. The hydrogen would then be used to produce electricity, either by a turbine or a fuel cell or sold for industrial use.

Coal is the workhorse of the U.S. electric power sector and is used to generate more than half the electricity the nation consumes. It is also America's most abundant fossil fuel, with supplies projected to last 250 years or more. The ultimate goal for the prototype plant, the Energy Department said, is to show how new technology can eliminate the negative environmental impact of coal combustion, allowing the U.S. to exploit its domestic energy resources and reduce its dependence on foreign oil. Combustion of fossil fuels in power plants and automobiles produces 82% of all U.S. airborne emissions, and the burning of coal accounts for a disproportionate share of air pollution.

Virtually every aspect of the prototype plant will use cutting-edge technology, DOE officials explained. If it works, FutureGen could become a model hydrogen-production facility, making fuel for cars powered by fuel cells. "We're envisioning a plant that produces multiple products," explained Robert S. Porter, communications director for the DOE's Office of Fossil Energy.

A power industry consortium will manage the project and will provide at least 20% of the costs, he added. How-ever, a detailed project timeline, the nature of the consortium, and other specifics have yet to be determined. "Some kind of government solicitation, hopefully by the end of this year," will delineate the requirements of prospective consortium members, Porter added. At this point, the DOE anticipates a two-stage, 10-year program (see table and Figure 2).

The future of coal-fired plants?An artist's concept of FutureGen, the DOE's vision of the zero-emission, coal-fired power plant of the future. The DOE has committed to invest $1 billion in the "cutting-edge" technologies that FutureGen will employ. Courtesy: U.S. DOE

Project definition, engineering, procurement, and construction are expected to take five years (less time than it typically takes to permit and build a conventional coal-fired plant) and would be followed by five years of operation, during which the project would serve as a test bed for new technologies. The DOE's National Energy Technology Laboratory in Pittsburgh did FutureGen's conceptual engineering.

Feasibility under attack
Although FutureGen has yet to generate any power, it has already generated plenty of skepticism. Coal gasification is a mature technology in the chemicals industry, which uses the process to create feedstock for ammonia and other chemicals and fine chemicals. But it's "still an edgy technology" for generating electricity, according to Robert S. Giglio, research director of Foster Wheeler Corp., Livingston, N.J. "The most economical way to make hydrogen is from methane natural gas." Extracting hydrogen from coal wastes 30% of the fossil fuel's latent energy, he explained.

Besides that, "DOE's numbers are bogus," complained energy consultant David Wojick of Star Tannery, Va. "Their budget and schedule would be tight even for a conventional coal-fired power plant with [selective catalytic reduction equipment] and a scrubber." FutureGen makes no allowance for the uncertainties inherent in taking on a research project, he added. "Porter J is a typical R&D guy who has no idea how much things cost."
Nonetheless, FutureGen's approach is "really a sure-fire way to have a clean plant," Giglio conceded, because "you really can't achieve zero emissions from the back end." It's easier to eliminate the pollutants in coal such as nitrogen oxides (NOX) and sulfur dioxide (SOi) at the front end than at the back, where they end up dispersed in flue gas, he explained. The plan is for FutureGen to clean SC>2 and NOx from the coal gases and convert them to byproducts such as fertilizers and soil enhancers. Mercury also would be removed, and CC>2 would be captured and sequestered in deep, underground geologic formations (see box).

Six thousand feet under

The DOE said it expects to initially capture at least 90% of the COa that FutureGen produces; adding that advanced technologies could eventually achieve nearly 100% capture. Once captured, the CO2 will be injected deep underground. Potential graves include saline aquifers thousands of feet below the surface, depleted oil or gas reservoirs, and unmineable coal seams or basalt formations. Once entombed, the greenhouse gas would have little chance of escaping into the atmosphere.
The sequestration step is projected to add about $320 million to FutureGen's tab.

Most of the funds will be spent on site evaluations, drilling of injection wells, and design and construction of the CO2-disposal system. The DOE explains that "the size of the plant is driven by the need for producing commercially relevant data, including the requirement for producing one million metric tons per year of CO2 to adequately validate the integrated operation of the gasification plant and the receiving geologic formation."

The department's long-term goals for the overall plant are equally ambitious. The project aims to "validate the engineering, economic, and environmental viability of advanced coal-based, near-zero emission technologies that by 2020 will: (1) produce electricity with less than a 10% increase in cost compared to non-sequestered systems; (2) produce hydrogen at $4.00/million Btus (wholesale), equivalent to $0.48/gallon of gasoline, or $0.22/gallon less than today's wholesale price of gasoline."

For its part, The Natural Resources Defense Council said it supports the rapid deployment of modern coal-gasification plants that capture carbon and store it in secure geologic formations. But David Hawkins, director of the environmental group's Climate Center, added that plants such as FutureGen must be accompanied by increased use of renewable energy and energy-efficient technologies in a three-part strategy to cut emissions of greenhouse gases. "We need to achieve major cuts in global warming emissions long before we stop using fossil fuels," he said.

Will carbon sequestration work?
Fossil fuels will remain the mainstay of electricity production—even in the U.S.—well into the 21st century. Because coal-fired power plants produce the lowest-cost electricity and coal is abundant, America's economic and energy security depend on the continued use of the fuel. But coal is an inherently dirty fuel; it contains more pollutants than oil or gas, and burning coal or any fossil fuel releases the pollutants into the atmosphere.
Fossil-fuel combustion also releases carbon dioxide, the primary greenhouse gas that causes global warming. Although the U.S. has yet to classify CC>2 as a pollutant, emissions of the gas are already being regulated under the Kyoto Protocol, and it is a foregone conclusion that all nations will eventually have to limit or reduce the amount of carbon they release into the atmosphere.

One way to do that is to separate out carbon at the point of combustion and capture and isolate it in a process known as sequestration. Sequestration techniques now under study range from injecting CO2 underground or deep into the ocean to having forests absorb the gas. One objective of the FutureGen project is to explore the feasibility of several of these techniques.

The cost of sequestration techniques will also be scrutinized. The DOE puts the cost of sequestration using existing technologies in the range of $100 to $300/ton of carbon emissions avoided. A goal of the FutureGen program is to employ advanced technologies to reduce that figure to $10 or less by 2015. Given the inevitability of carbon regulation, it is thought that achieving that goal would save the U.S. trillions of dollars.

This article was published in POWER Magazine in its May2003 edition