All Fired Up Over Clean Coal
It was a disturbing sight: many peaks in Vermont's Green Mountains were bald or turning a foreboding brown. The trees were dying from acid rain caused by pollution from coal-fired power plants in the Midwest. The images still haunt Dr. Robert R. Holcomb, a children's neurologist at Vanderbilt University Medical Center and an ardent environmentalist. His 1995 trip to Vermont spurred a lifelong quest to combat fossil-fuel pollution.
Nine years later, on Jan. 30, Holcomb unveiled his dream-come-true system for zapping pollutants at coal-burning plants before they can taint the air. It's an imaginative scheme -- and an impractical one, according to some physicists and engineers familiar with Holcomb's work. But even his toughest critics admit that breakthroughs are urgently needed to eliminate smokestack emissions. And some of the critics have their own designs on the drawing board.
The urgency stems from the rapid growth in energy demand among developing countries such as China, plus the fact that oil output may peak as soon as the 2010s. Even with steady advances in wind and solar power, cheap and abundant coal is expected to take up most of the slack. "China is a high priority for us," says Holcomb. "They need energy, and their air pollution is horrendous."
Holcomb calls his technology the Electron Stream Carbon Dioxide Reduction system. But that's a misnomer. The system also targets sulfur dioxide (SO2) and nitrogen oxides (NOx). And it doesn't just reduce them -- it eradicates them by splitting the polluting molecules into benign atoms. CO2, for example, gets carved up into carbon and oxygen atoms.
Scientists say this portion of Holcomb's scheme is possible. But they scoff at one of his claims: that the technology could transform the pollutants into atoms using just a small portion of a coal-fired generator's energy output. Holcomb asserts that by recycling the heat and recovered oxygen back into the coal furnace, "the CO2 converter would use only 10% of the energy generated" by a power plant.
Trouble is, that would violate physical laws, argues Hans-Joachim Ziock, a physicist and energy expert at Los Alamos National Laboratory. Breaking the chemical bonds that glue atoms together into molecules takes even more energy than was used to create them, he explains. Since the energy released by burning coal stems mainly from oxidizing carbon (turning it into CO2), reversing the process would require all that energy output, and then some. "I'm missing the magic here," agrees Henry J. Cialone, senior vice-president for energy services at Battelle Memorial Institute, a think tank in Columbus, Ohio.
Yet Holcomb has some hopeful supporters. "I'm confident there's no hoax here," declares J. Alex Silver, head of energy consulting at Black & Veatch Corp., an Overland Park (Kan.) engineering firm. Holcomb hired Black & Veatch to test his prototype CO2 converter in January. Says Silver: "We definitely were getting dissociation of CO2 [into carbon and oxygen], and that by itself is very neat." Still, he adds, "the big question is, how much energy was going into the converter?"
Silver intends to measure that during his next round of tests, probably in March. If the process lives up to Holcomb's claims of just a 10% drain on power-plant efficiency, "its potentials would be profound," Silver says. New coal-fueled power plants convert 30% to 35% of coal's energy into electricity. Most existing plants manage just 18% to 20%. So if Holcomb's gear needs only 10% of the energy output, a new plant could be pollution-free and just as efficient as many of today's generators.
The key to Holcomb's process is a plasma arc -- a sort of superhot blowtorch. When it zaps CO2 and other gaseous oxides, the intense heat strips off their electrons, then cleaves the molecules into ions (atoms lacking their usual electrons). Since ions are highly reactive, they would ordinarily pop back together into polluting gases when they emerged from the plasma. To prevent this, Holcomb routes the ions through a charged tungsten mesh that is fed a constant supply of electrons. There, the ions pick up their missing electrons and emerge as regular carbon, oxygen, nitrogen, or sulfur atoms. "At the end of the day," says Holcomb, "we burn coal, create energy, and collect substances like carbon and sulfur in traps."
Skeptics may dismiss Holcomb's process, but his goals are hardly unique. In the late '90s, Los Alamos' Ziock led an international research team in a program to curb pollution while boosting power-plant efficiency -- all the way to 70%. In 1999, the team formed the Zero Emission Coal Alliance, and last year spun it into the private Zeca Corp. of Santa Fe.
Zeca is developing a very different strategy from Holcomb's. Its plan to eliminate smokestack pollution hinges on avoiding combustion altogether, says Zeca CEO Alan A. Johnson. With Zeca's process, the hydrogen in coal would be extracted and fed to a new type of fuel cell, which would chemically convert the hydrogen into electricity and water. Zeca's work is funded by nine stakeholders, including Canada's Ontario Power Generation, Arch Coal in St. Louis, Germany's Rag Coal International, and equipment giant Caterpillar in Peoria.
Today, Zeca's fuel cell is a little lab unit, "just one inch square," says Johnson. But Zeca plans to build a working 1-megawatt pilot plant in two years. Long before that, Holcomb insists, independent tests will verify that his CO2 reduction system "can do the job for less than any other technology." By one route or another, the race to zero emissions has begun.
By Otis Port in New York