American utility consumers face a compelling generational challenge: satisfy the need for a reliable power supply, at a reasonable price, while also reducing greenhouse-gas emissions and building...
The Carbon Conundrum
the entire generation fleet-will be more than 50 years old, with a tenth over 60 years old. By 2025, two-thirds of the coal-fired fleet will be over 50 years old.
Yet proposals for new coal-fired generation are still few and far between. Much of that hesitation comes from the environmental concerns that coal-fired generation always raises. Few investors or utilities are especially sanguine about the prospects of coal-fired plants, particularly with uncertainty over limits on carbon dioxide emissions.
While utilities don't contribute all of the human-induced CO 2, the sector does produce around 37 percent of it. The other big contributor is vehicles, adding another third to the total, and then a potpourri of other sources, including the burning of natural gas for heating. "If you look at the different CO 2-producing sectors and ask where could you capture this stuff from most easily, it's not going to be homes or vehicles. … The focus is going to be on the utility sector," says Scott Klara, product manager, sequestration at the National Energy Technology Laboratory (NETL). And, he notes, there are capture technologies that exist today that could be used in power plants. "In fact, in some instances [capture technologies] are used where there's a market for CO 2."
A Not-Quite-New Idea
In fact, the idea of sequestering carbon dioxide isn't new-oil and gas companies have been doing it for years, under the name enhanced oil recovery (EOR). CO 2 is pumped back into wells and down into the oil or gas formation, to aid the wells' productivity levels, by making it possible to pump more of the remaining oil or gas to the surface.
Until fairly recently, EOR wasn't studied as a specific means of carbon sequestration for the power industry. That changed with the Weyburn project in Saskatchewan, Canada.
The Weyburn project is primarily an oil recovery project, but various monitoring devices were installed in 2000 to assess the permanence and safety of CO 2 storage within the oil formation. Weyburn gets its CO 2 piped from the Dakota Gasification Co., a synthetic fuel plant nearly 20 miles away in Beulah, N.D.
Scientists are glad to have the monitoring data for CO 2 sequestration at an EOR project, but even before Weyburn, there wasn't much doubt that oil and gas reservoirs were workable solutions for carbon sequestration.
"Oil and especially gas reserves have held [their contents] for millions of years," observes Klara, "so those reserves have shown great containment already." Adds Howard Herzog, principal research engineer at MIT's Carbon Sequestration Initiative, "When the Weyburn project is done and [CO 2] has been sitting for a time under pressure, that will be interesting to see." Herzog says Weyburn is operating as expected. "It's confirmed what people believed" about EOR and CO 2 storage, he says.
The potential volume of carbon sequestration in oil and gas reservoirs is substantial. Current worldwide CO 2 production is estimated at around 6.2 gigatonnes annually. The NETL estimates that oil and gas reservoirs could provide storage for nearly 1,750 gigatonnes of carbon