Recent field trials undertaken by North American plastics industry association EPIC show that the use of municipal plastic residues as a feedstock in gasification may provide an alternative source of clean energy to help meet the increasing global demand for electricity.

Gasification has been in use for more than half a century and is a proven technology currently in operation all over the world. Although often confused with incineration, gasification is significantly different. For one, it uses an atmosphere that has very little, if any, oxygen. This prevents sulphur and nitrogen oxides from forming. Gasification also operates at very high temperatures and produces carbon monoxide and hydrogen (instead of the carbon dioxide and water produced through incineration). Another dramatic difference is that gasifiers produce a "syngas" free of dioxins and furan compounds.

Until now, gasification plants relied primarily on coal and petroleum by-products. But two separate field trials conducted by EPIC at Enerkem Technologies' Sherbrooke, QC, facilities clearly demonstrate that municipal plastic residues are an excellent alternative feedstock.

The tests involved two samples of waste plastic from an Ontario municipality. The first included plastic film and the second involved a mixture of #3 to #7 plastics. Both samples were destined for landfill.

Results showed that the plastics offer high energy efficiencies in gasification,with the energy in the feedstock largely converted to syngas. Almost 72 per cent of the feed energy was converted to syngas in the first sample and close to 77 per cent in the second sample (approximately 15 per cent of the original feedstock was lost in cooling the gas). The syngas from both samples was then burned to determine atmospheric emissions. Tests conducted by a third-party, independent consultant showed that all emissions were well below the allowable limits set out under the A-7 guidelines for the province of Ontario (which are among the most stringent in the world). The measured levels of dioxins and furans, as an added note, were as much as 16 times lower than the Ontario emission limits.

The gasification of the two samples resulted in a tiny amount of solid residues - both of which showed that any quantities of heavy metals, cadmium, chromium, lead and mercury were well below the limits of detection.