"From his desk in an office in Chicago, Jeff Smith has a bird’s-eye view of the American landscape. Combing through a huge database of information compiled by the EPA, he can, almost literally, peer down every smokestack in the nation and figure out what’s going on inside.

And what he sees is heat. Waste heat—one of the country’s largest potential sources of power, pouring up out of those smokestacks. If it could be recycled into electricity, that heat would generate immense amounts of power without our having to burn any new fossil fuels. By immense, I mean, speaking technically, humongous. Even after he’s winnowed the nation’s half a million smokestacks down to the most likely customers, that leaves twenty-five thousand stacks. “An astronomical number,” Smith says...

...The biggest sources of waste heat are some gas turbines used to generate power, but there are endless other examples. “Let’s look at Florida,” he says. “Here’s a Maxwell House coffee roaster in Duval County. They’re roasting beans, so all that heat has to go somewhere. About twelve megawatts’ worth of potential electricity is going up the stack.” Casten could take the equipment he sells, a “waste-heat recovery boiler,” and stick it on top of the stack. “Basically, there’s a network of tubes with water in them. The heat would hit one side of it, produce steam, and we’d use that to turn a turbine and generate electricity. It’s like any other boiler, just without a flame, because the heat is already there.”