At $2 per million BTUs of natural gas and $1 per million BTUs for coal, the wasted energy may go unnoticed. But, at $8 per million BTUs for natural gas and correspondingly higher coal rates, wasted heat is a valuable resource.

"We can recycle energy in two ways: either from the industry to make more power or from power generation to make heat for the industry," says Thomas Casten, CEO of Primary Energy, an Oak Brook, Illinois firm specializing in recycled energy, at a conference in Charleston, West Virginia sponsored by Industries of the Future. "You have purchased less electricity. You've purchased less process fuel. You're still making the same amount of finished goods, but you emit less waste energy."

To recycle waste heat, on-site generation is necessary. Industrial heat cannot be moved through the pipes and into a power plant while the heat from generators cannot be transported to an industrial facility. The ultimate result: Instead of a 35 percent efficiency rate, it could be anywhere from 66 percent to 96 percent efficient -- the amount of input that is actually converted into heat or power. Casten says that his firm has a plant in Kentucky that is at the top end of that scale.

With the U.S. Energy Information Administration saying that the expected demand for power will rise by 50 percent over the next two decades, the country will need every resource possible. Along those lines, the U.S. Environmental Protection Agency issued a report that shows a potential 95,000 megawatts for converting waste energy from industry into heat and power. Of that, the United States' share would be about 10,000 megawatts total recycled energy generation.

"We use trillions of BTUs every hour of every day," says Daniel Stinger, CEO of WOW Energies. "That's a lot of energy that could be recaptured and reused but instead it is going up smoke stacks and into the atmosphere."

The Costs

That air is going out the stack at between 300 degrees Fahrenheit and 800 degrees Fahrenheit. It's all available to reuse and convert to mechanical power, says Stinger. Combined cycle and co-generation power plants do just that but they perform best when the steam coming out the other end is 800 degrees Fahrenheit or more. So, there's a huge window of opportunity to capture energy in those refineries and industries where the wasted heat is released at 300-700 degrees Fahrenheit.

Put simply, it is like boiling water and then using the steam to power other things in the house. But for all practical purposes, the steam is just released and lost forever. Moreover, it takes a lot of energy to create that steam. So, the idea is to not just recapture and reuse the steam but to use less energy to produce it.

Reusing energy in the form of waste heat recovery has been popular in Europe for years. Much of it comes in the form of combined heat and power systems. Many industries there produce about 20 percent of their power this way while those in this country generate 7.5 percent by recycling energy, says Primary Energy's Casten.

The major thrust for waste heat recovery in the United States began in the early 1980s when Congress forced utilities to purchase excess power generated by such companies as Dow and DuPont. These companies wanted to reuse the steam in their plants but, at the time, most were not allowed to sell the excess power produced by their facilities to their utilities or in some cases they wouldn't receive a high enough price for the surplus to make those projects viable. Their ingenuity and the subsequent congressional action taken ultimately spawned the creation of independent power producers that used high efficiency technologies such as combined cycle and co-generation power systems.

"There are only two paths toward achieving big reductions in greenhouse gas emissions," says Paula Dobriansky, U.S. undersecretary of state for global affairs, in an interview with the Financial Times. "One is to use existing technologies at the expense of economic growth. The other is to use breakthrough technologies that transform how we produce and consume energy and allow us to reduce emissions, while continuing to grow and to improve the world's living standards. The second course is the only acceptable, cost-effective option."

But, cost is a deterrent. Central generation last year was reported to run $890 per kilowatt of new capacity. Local generation, meantime, costs $1,200 per kilowatt. However, with a big plant, there's a need for transmission and distribution -- all of which adds to the expense of building a central power plant and which makes on-site power more attractive.