by Sally Wasikowski, Chem-Mod
These are good times for natural gas. The U.S. Energy Information Administration recently more than doubled its estimates of recoverable domestic shale gas to 827 trillion cubic feet—more than 34 times the amount of gas the U.S. uses each year. That, combined with other natural gas sources, might be enough to last a century at current consumption rates.
Time magazine put shale on its April 11 cover with the headline “Why Shale Can Solve the Energy Crisis.” President Barack Obama even offered his endorsement, declaring in a speech on energy March 30 at Georgetown University, “The potential for natural gas is enormous.”
The push for natural gas is understandable. It’s domestic, abundant and relatively clean-burning—desirable characteristics for baseload generation. Nuclear power suffered a setback after the post-earthquake meltdown at Japan’s Fukushima Daiichi Nuclear Power Station, and wind and solar are years from reaching their potential. What other options do we have?
We have coal—domestic, abundant and increasingly clean. It would be a mistake to ignore clean-coal technologies amid the euphoria about natural gas. We have the technology to reduce coal-fired power plants’ emissions significantly, among them mercury, sulfur dioxide and nitrogen oxide. In addition, we are making significant strides in addressing carbon dioxide emissions with coal gasification and carbon capture.
The U.S. has more recoverable coal than anywhere in the world, with domestic reserves vast enough to last more than 200 years, according to the Department of Energy (DOE). Coal fuels nearly half of all electricity generated in the U.S., one of the reasons U.S. electricity rates are among the lowest in the world.
Coal is not without its challenges. Coal-fired power plants are the No. 1 source of CO<sub>2</sub> emissions in the U.S., as well as the largest source of mercury emissions. Mercury has been linked to health problems including brain, kidney and lung damage, and regulators rightly have moved to control its emissions.
One solution is a coal-additive system in commercial use at eight power plants. Chem-Mod’s microencapsulation process features a dual-injection sorbent system using a liquid oxidation agent and a noncarbon-based sorbent to remove mercury and other pollutants. The additive is applied to coal as it moves through the feeder on its way to the pulverizer, and the solid sorbent creates the surface required to capture and hold the oxidized mercury in a ceramic-like matrix consisting of aluminosilicates.
This technology can help power plants meet and exceed the Environmental Protection Agency’s (EPA’s) proposed emissions standards, including Clean Air Mercury Rule standards. Testing at the University of North Dakota’s Energy & Environment Research Center showed that this cost-effective technology reduces mercury air emissions up to 98 percent, SO2 air emissions up to 75 percent and NOX air emissions up to 31 percent. Locking the contaminants into this stable chemical structure means they are not free to leach into rivers and eventually the food chain.
Still, CO<sub>2</sub> emissions represent a hurdle for coal. But coal gasification, a process in which coal is heated to the point where it turns into a gas, can cut the formation of CO<sub>2</sub> 40 percent compared with a typical coal-combustion plant. Though worldwide only four integrated gasification combined-cycle (IGCC) systems exist, they show promise.
In IGCC plants, synthetic gas is cleaned of its hydrogen sulfide, ammonia and particulate matter and burned in a combustion turbine, which drives an electric generator. Exhaust heat from the combustion turbine is recovered and is used to boil water, creating steam for a steam turbine-generator. Working together, these cycles achieve high power generation efficiencies. Higher efficiencies mean less fuel is used to generate the rated power, resulting in better economics and fewer greenhouse gases.
If IGCC technology is combined with technology to lock up contaminants, coal-fired power can achieve gas power’s efficiencies and eliminate the issues associated with fly ash disposal.
Carbon capture offers another, longer-term strategy for clean coal. The International Energy Agency estimates carbon capture and storage could reduce CO<sub>2</sub> emissions from coal-fired plants more than 85 percent. Essentially, carbon capture strips CO<sub>2</sub> from fossil fuels before or after they’re burned. The CO<sub>2</sub> is then piped back into the earth where it stays for thousands, if not millions, of years.
Though carbon capture is in the trial stage, it would be folly to abandon it and other efforts to produce clean energy from coal. Coal, along with every fuel, has its shortcomings. Controversy exists around hydraulic fracturing, or “fracking,” which allows producers access to shale gas but has raised concerns about wastewater contamination, spills and air pollution.
To become dependent on a single source of energy is a mistake, one we’ve learned the hard way from oil. Coal deserves a place in our energy mix, and technology can help keep it there.
Sally Wasikowski is president of Chemical Modification Management Inc., a clean-energy management company.