“I am going to make sure that we’ve got a clean energy economy…”“And the best way for us to create good jobs is through clean, renewable energy…”Senators Barack Obama and Hilary Clinton spoke in Kentucky and Indiana this month, rallying crowds before Tuesday’s primary election. Each candidate told supporters that developing clean and renewable energy sources would top their to-do list in the White House. Both candidates have expressed a desire to invest in one such source: clean coal. But what exactly is clean coal?“It really refers to a suite of technologies…”This is Tom Sarkus, with the National Energy Technology Laboratory.“…anything from emissions control on existing coal-fired power plants to new power generation technologies such as IGCC, or integrated gasification combined cycle.”In an IGCC plant, coal isn’t burned. Rather, it’s exposed to heat, steam, and pressure to set off a chemical reaction. The results of that reaction are something called “syngas.” The syngas then powers two kinds of turbines to generate electricity. And the by-product heat is captured and used to start the whole process over again. There are only two IGCC plants operating the U.S. now. Tom Sarkus says they put out about a tenth of the pollution a regular coal plant does and they’re efficient. But utilities aren’t exactly jumping on the IGCC bandwagon.“It can cost 10 to 20 percent more than a conventional coal-fired power plant.”IGCC may be a promising clean technology for new plants. But it doesn’t solve the remaining problems with coal-fired power plants. Many utilities have managed to reduce the acid rain-causing emissions by adding devices called “scrubbers.” They’ve managed to reduce the tiny particulate matter that comes spewing out of stacks. But Sarkus says the next challenges include dealing with mercury emissions...“And the next one that’s looming on the horizon, as you know, is carbon dioxide.”Carbon dioxide is a greenhouse gas, contributing to global warming. Both democratic presidential candidates want to reduce carbon emissions to 80 percent of 1990 levels. Both want to develop clean coal. Both say they would invest $150 billion dollars over a decade in renewable energy. Obama’s campaign did not return repeated phone calls. But his Web site says he’ll support clean coal, as well as consider banning new traditional coal facilities. Hilary Clinton’s senior energy advisor, Dan Utech, gets specific about how Clinton would spend that renewable energy money to deal with carbon emissions.“One of the purposes of that money would be to fund ten large-scale projects to test this capture and storage technology.”Coal plants aren’t required to capture and store carbon. But many researchers, politicians, and industry representatives believe it’s only a matter of time—in a new presidential administration—before they are. E.on-US executive Paul Thomson believes carbon legislation is a strong possibility. Thomson says his own utility is investing in about dozens of projects worldwide to figure out ways to contain or store carbon. But he says the technologies aren’t ready for use on a commercial scale.“Sequestration, the storage of carbon dioxide underground, which is thought to be the most likely good answer for us, is very feasible. In various ways the technology has been proven. But our industry is a large scale industry, and that’s what we need to prove out.”Meanwhile, there’s no sign we’ll be reducing our coal consumption any time soon. Rather, we’ll be waiting to see how a new president approaches this resource that’s abundant but imperfect.