Plastics converted to gaseous fuel
Researchers at Northeastern University in the USA have designed an apparatus that subjects non biodegradable plastics to pyrolysis to produce a gaseous fuel. The process is a modern variant of that developed by Scottish engineer William Murdoch in the 1790s, to produce gas fuel from coal for lighting.
The waste combustor developed by Professor Yiannis Levendis and his researchers at North Eastern University would be burned in a separate combustor to generate steam to power an electric generator, although this is already undertaken directly in municipal waste to power plants, several of which are presently in service in the UK.
The snag in any process that converts plastic to usable fuel is pollutants, particularly hydrogen chloride resulting from the presence of PVC, plus other toxic gases. In a waste to power plant, the hydrogen chloride is removed by scrubbing the effluent gas from the plant. In a traditional coal to town's gas plant, the main problem was sulphur, which was removed by passing the gas over iron filings. Prof Levendis has not disclosed how his process deals with potential pollutants except to say that, the apparatus is designed to convert plastic waste into clean energy while minimising the release of harmful emissions.
The destructive distillation of bulk plastics is likely to produce a mixture of gases and could not be used as a direct replacement for natural gas. It could, nonetheless be piped and used at a location separate from the waste disposal plant at which it was being produced.
The alternative is carefully recovering and sorting plastics for re-use, which is also being done in the UK and elsewhere, but this is expensive, unless the plastics are pre-sorted by whichever source is disposing of them.
The prototype was featured at the fifth annual MIT Energy Conference in March 2010. The team worked for nine months on the research, which, for the undergraduates, was their senior capstone project.
The team members included Jeff Young, Shane McElroy, Jason Lee, David Laskowski, David Garufi and Paul Conroy, all senior undergraduate students; and Brendan Hall and Chuanwei Zhuo, who are graduate students, both of whom plan to continue working with Prof Levendis on the project.