Mon November 26, 2012
Using Trash to Create Energy
When it comes to trash, you can stick it in a landfill. But using it to create energy is an increasingly popular option.
Sometimes that trash is literally burned to fuel a process. Sometimes the methane that's created by landfills is used for electricity. Sometimes companies use technology that to capture the waste heat from their systems, and re-use it. (I wrote about one such plant several years ago in West Virginia.) And recently, scientists unveiled a new material that's much more effective at converting waste heat to electricity.
The material is based on the common semiconductor lead telluride, an environmentally stable material, and is expected to convert 15 to 20% of waste heat into useful electricity. That’s nearly 30% more efficient than its predecessor, making it far and away the most efficient thermoelectric material ever.
And here in Louisville, tires are being converted to energy, reducing air pollution and saving landfill space. In yesterday's newspaper, Jim Bruggers of the Courier-Journal took a look at the process at Louisville's CEMEX plant:
The plant started burning tires in place of coal in 2010, following testing in 2009.
The changeover has helped Kentucky waste managers keep an estimated 2 million tires out of landfills, while the plant has burned as much as 24,000 fewer tons of coal, said Shannon Graves, the environmental manager at the plant.
Tires now make up about 15 percent of the plant’s fuel, with coal and some pet coke, a residue from petroleum distillation, supplying the rest, she said. The tires are kept in semi-trailers, out of the rain, and are loaded and guided onto a conveyor track by three workers.
This appears to be a win-win. The company breaks even on cost, and tires that would otherwise be discarded are combusted in a high-heat kiln and used to make cement.
India is experimenting with power plants fueled by garbage (which is bad news for trash pickers, according to this Associated Press article). In Sweden, there are numerous waste-to-energy plants...so much so that the country has begun importing trash to burn.
I called LG&E to see if there's any way the company's power plants capture the waste heat generated by their machines, and spokeswoman Liz Pratt says there's not. But she added that the combustion process makes the inside of the power plant so warm, the company doesn't need to have any additional kind of heating mechanism to keep the building heated in the winter.