♦EXPLORER: I guess the first question is everyone's first question on this topic: What will be the environmental impact of pursuing clean coal technology?
WILLIAM AMBROSE: First and foremost, clean coal technology (CCT) is expensive, and environmental benefits from clean coal should be balanced against costs. Having said this, I must also point out that clean coal has the potential to reduce emissions to extremely low levels. Clean coal involves stripping of minerals and other impurities via high-temperature and high-pressure gasification with capture of CO2 and hydrogen. Minerals and impurities that are stripped from coal are oxides of nitrogen and sulfur (referred to as NOx and SOx), mercury, sulfur, arsenic, metals such as lead and cadmium and ash.
Actually, clean-coal processes have been under way in the United States for more than 40 years since the Environmental Protection Agency (EPA) began operations in December 1970. For example, from 1970 through 2003, particulate emissions from coal-fired power plants declined by 87 percent, and SOx emissions fell by 35 percent, although electricity from coal increased by almost 180 percent.
♦EXPLORER: While recently watching an old episode of The West Wing, someone asked President Bartlett about clean coal. He replied, "It's just a public relations gimmick. It doesn't really exist." I'm sure you disagree, but if you would, tell me how clean “clean” will be? And will it ever be clean enough to satisfy environmentalists?
AMBROSE: Coal-gasification technology can achieve reductions in mercury, arsenic and sulfur up to 80 percent, as well as CO2 capture at levels of as much as 90 percent. Integrated gasification combined-cycle (IGCC) technology can result in even greater reductions.
There are more than 420 coal gasifiers worldwide. Gasification involves high-pressure and high-temperature (commonly >1,000 psi and >2,500 ºF, respectively) coal combustion with air or oxygen injection, producing a syngas rich in carbon monoxide, hydrogen sulfide, and hydrogen. This syngas is then processed to remove contaminants and is also flowed through a “shift” reactor that uses steam and various catalysts to convert the carbon monoxide to carbon dioxide.
IGCC plants, of which there are currently four worldwide, take the process one step further by using the syngas to drive a combustion turbine and steam to power a second turbine, resulting in increased overall efficiency. Gasifiers typically involve efficiencies in the 30 to 40 percent range, but IGCC plants can boost overall efficiency to >45 percent.
However, clean-coal technology comes with an appreciable price tag. The costs of capture, transport, and storage of CO2 range from $25 to more than $50 per metric ton, depending on a variety of factors that include pre- versus post-combustion carbon capture, new plant versus retrofitted plant, type of gasifier feedstock and distance of new plants from user electric load. Operational costs are also estimated to be up to $15 per metric ton. The overall energy penalty of installing CO2-capture equipment could reduce plant efficiency by as much as 40 percent.
Additional costs can be incurred through construction of new CO2 pipelines or pumping costs associated with CO2 sequestration in deep, brine-bearing formations.
All these additional costs can increase the cost of electricity by 25 to 50 percent or more.
To place these potential costs into perspective, $50 per metric ton may not seem like a great amount, but consider what the costs would be to capture and sequester all of the CO2 emitted annually from coal-fired power plants in Texas. According to the Energy Information Administration (EIA), Texas accounted for 152 million metric tons (Mt) from coal-fired power plants in 2008. To capture and sequester all this CO2 without economic benefit from enhanced oil recovery (EOR) or enhanced coalbed methane recovery (ECBM) would cost plant operators in Texas ~$7.6 billion per year. Fortunately, Texas and neighboring states contain a variety of oil plays with reservoirs having EOR potential from injection and miscible displacement of oil with CO2.
EOR from miscible-CO2 flooding in the Permian Basin in west Texas and southeast New Mexico has been used as a tertiary oil recovery strategy since 1971, where >1 billion barrels (Bbbl) of oil has been produced using CO2-EOR. A 2006 study by Advanced Resources International concludes that an additional 5.6 Bbbl of oil from 127 reservoirs is technically recoverable in the Permian Basin using miscible-CO2 flooding. A 2005 study by the Bureau of Economic Geology (BEG) suggests that >4.7 Bbbl of oil is technically recoverable from CO2-EOR in the Texas, Louisiana, Alabama and the Florida Gulf Coast.
The U.S. oil industry has injected over 600 million tons of CO2 and is currently producing ~250,000 barrels of oil per day with EOR.
According to economic analysis by the Center for Energy Economics at the BEG, onshore CO2-EOR projects break even at $60-80/barrel for $100-200 per ton of CO2.
♦EXPLORER: Talk about the natural gas vs. clean coal debate. There are those, obviously, who think we should be pursing natural gas as an energy source more than clean coal.
AMBROSE: Natural gas continues to make inroads at the expense of coal as a source of electrical power generation, owing to low gas prices. Moreover, natural gas is an extremely versatile fuel, used in residential, commercial, industrial, and transport sectors of the economy. Another advantage that natural gas has over coal is that the latter is the most carbon-intensive of the fossil fuels.
On the plus side for coal, traditional coal-fired power plants (referred to as pulverized-coal or “PC” plants) in Texas are still economically competitive with gas, even with current low gas prices. This is because the capital investment in most PC plants is paid off, and lignite plus Powder River Basin coal is still cheaper on a BTU basis.
♦EXPLORER: If CCS and CCT work, what do are the benefits for the country in terms of energy independence?
AMBROSE: The United States has a superabundance of coal, with almost six quintillion BTU of energy-equivalent resources – more than eastern Europe and the former Soviet Union (FSU) combined. Harnessing these vast resources could help the United States to lessen its dependence on foreign energy sources, particularly with coal-to-liquids (CTL) technology that converts coal to gasoline.
However, achieving complete energy independence via increased reliance on coal is limited by the high costs of either refining it into liquid fuel or CCS associated with clean coal.
♦EXPLORER: What about the regional and nation politics of the issue? I'm sure this is an easier sell in West Virginia than Florida, or Kentucky than Oregon. And, nationally, which administration in the past few decades was most receptive to the pursuit of this?
AMBROSE: States such as Illinois, West Virginia and Wyoming, with significant coal resources, tend to lobby for coal regardless of local party constituencies. For example, seven states vied for the former FutureGen project. These included Illinois (who was awarded the prize), Texas, Kentucky, North Dakota, Ohio, West Virginia and Indiana. The FutureGen initiative was associated with the George W. Bush administration, and other recent administrations have also shown interest in clean coal.
♦EXPLORER: What, personally, attracted you to this issue?
AMBROSE: As chair of the EMD Coal Committee, I am interested in all aspects of coal, even those that are new and in which production technology is still being developed.
♦EXPLORER: What IS the overview of CCT and CCS in America right now?
AMBROSE: This is an excellent question, and the debate about the future of CCT and CCS in America continues. This is an issue that BEG Director (and AAPG member) Scott Tinker considers from multiples perspectives that include the “possible” (science and technology), “doable” (regulatory and legal) and most importantly, “sensible” (economics and climate impact in time frame needed).
CCT is struggling to move ahead in today’s harsh project-financing climate and in the context of current low gas prices. However, effective and safe CCS has been successfully demonstrated with large commercial-scale USDOE projects that include the BEG’s Cranfield (Mississippi), Hastings (Texas) and offshore Texas Gulf Coast projects.
The Cranfield project continues to make progress, and is the first project to inject >1 Mt of CO2 into subsurface brine formations. The Cranfield project is part of a large-scale CO2–EOR-CCS operation operated by Denbury Resources using naturally sourced CO2 from Jackson Dome, Mississippi.
In addition, Weyburn oil field in Saskatchewan (Canada) has become the largest land-based CO2 storage project in the world, having sequestered >12 Mt. The feedstock for CO2 in Weyburn field comes from lignite in North Dakota, where the Dakota Gasification Company produces ~95 million cubic feet per day of CO2, transported via a 205-mile pipeline to Weyburn oil field.
Other related CCS projects include the Illinois Geological Survey’s Decatur project and the SECARB test at the Barry generating plant near Mount Vernon, Ala., which is preparing to capture CO2 from a coal-fired plant and transport CO2 via pipeline to store in a nonproducing zone in the Paluxy Formation in Citronelle oil field in southwest Alabama.
Brine storage has been tested successfully by BEG in the Frio Formation in southeast Texas, and upcoming large projects include the Midwest Geologic Storage Consortium Project at the ADM plant in Decatur, Ill.
These CCS projects are already demonstrating the technical feasibility of carbon capture and sequestration.