Power and Fuel From Plastic Wastes
In Pennsylvania, the department of environmental protection doesn’t regulate emissions from combustion units with a heat-input rating less than 2.5 million British thermal units an hour (MMBtu/hr) and, therefore, units sized less than 2.5 MMBtu/hr require no permits to begin burning, or gasifying, waste plastics. Eco-Clean Burners and Shea are finishing installation of an 800,000-Btu/hr plastic-burner unit at a greenhouse called Iannetti’s Garden Centre in Burgettstown, Pa. “Here at Iannetti’s is the first place we’ve installed one of these burners,” Shea says. “We haven’t actually run it yet. We’ve been installing it all summer and now we’re waiting for some cold weather to try it out and do some heating. By next spring we should be able to tabulate the numbers and see how effective it will actually be.”
He says the system is designed to gasify 30 to 33 pounds an hour of granulated waste plastic. Catalytic Pyrolysis of Waste Plastics While interest in combusting and gasifying plastic appears to be growing, there is another route to making practical use of all the waste plastics modern society produces. Through what it calls catalytic pyrolysis, Polymer Energy LLC, a division of Northern Technologies International Corp., has developed a system to convert waste plastics into liquid hydrocarbons, coke and gas, which can then be used as boiler fuel for power generation. “The technology uses lower temperatures than gasification—significantly lower—so it’s more energy efficient to produce,” says Kathy Radosevich, business development manager with Polymer Energy. Through “random depolymerization,” or selective breaking of carbon-to-carbon bonds, in addition to feeding in proprietary catalytic additives, the reactor melts and vaporizes waste plastic in one step at temperatures between 840 and 1,020 degrees F.
The company reports that, on average, 78 percent of every pound of plastic fed into the Polymer Energy system is converted to liquid hydrocarbons, coke and gas. The resultant coke can be further processed to produce additional fuel oil.
Polymer Energy’s catalytic pyrolysis system processes polyolefins like polyethylene and polypropylene with up to 5 percent other plastic materials, plus up to 25 percent additional nonplastic waste, such as paper, glass, sand and water—making it ideal for processing municipal wastes. Radosevich says the company has already sold nearly 20 of these systems in Europe, India and Thailand.
“The interest in the United States and Canada is huge but I expect that we won’t be marketing units in North America until next year some time,” she tells Biomass Magazine. Hitherto the markets for these units outside North America have been “more conducive” mainly because higher fuel prices in places such as Europe and India have increased the desire for such alternative-fuel production units. “In the United States I’m doing preliminary testing for EPA approval, although I don’t anticipate we’ll have any problems … The only item that would be of interest to EPA that I can think of would be any type of contaminants in the ash.”
According to Polymer Energy, the output oil contains no chlorine, sulphur, nitrogen or heavy metals. Any of that material would remain in the ash, which Radosevich says would differ on an individual usage basis depending on the average makeup of the plastic-waste feedstock. “What we would do is sample the input plastic and the [post-processed] ash, and cross-check that with local requirements the community has for permit approvals,” she says. Clearly there is growing interest in doing something different with waste plastic than dumping it in landfills or the oceans.
The global community must force itself to change its present path and become truly concerned about the environment in which its descendents will be raised, for what people do today affects everyone tomorrow. Ron Kotrba is a Biomass Magazine senior writer. Reach him at firstname.lastname@example.org or (701) 738-4942.