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[en] Full text: It is purely elemental, returning materials to their basic atoms through extreme heat and then recondensing them in useful ways. Plasma arc gasification is the latest advanced waste treatment (AWT)concept to hit our shores, courtesy of Zenergy Australia. According to its fans, plasma technology can eliminate all domestic waste to landfill and turn it into beneficial by-products. Japan has toyed with it for a decade, but the idea is now creating a bit of buzz, in the US in particular. Consultancy URS last year undertook a review of 16 advanced technologies for the City of Los Angeles and determined plasma arc gasification was one of the most promising. The Waste Management Association of Australia (VVMAA), however, is cautious - too many AWT projects here have failed to live up to their promises. Plasma arc gasification works on the same principle as a welding machine. An inert gas is passed through an electrical arc between two electrodes and becomes ionised (called plasma), reaching temperatures as high as 13,900°C. It is then injected into the plasma converter holding the waste. Zenergy is working with US technology company Plasma Waste Recycling (PWR), which says it can convert 80 per cent of waste to syngas, a mixture of carbon monoxide and hydrogen that can be used to generate renewable electricity. The inorganic compounds in the waste come out as a solid, either molten metal to be cast as scrap steel or a slag that can be used as a building material aggregate or spun into mineral wool. “The plasma arc process is the next generation for AWT plants as there is no incineration involved, no fly ash, no bottom ash and nothing left to landfill,” said Zenergy Australia's Paul Prasad. He estimates a plant could convert up to 175,000 tonnes of household waste a year into energy or reusable by-products. Technically, it also gets around Australia's fears over incineration, though whether that is really the case in practice remains to be seen. Prasad says there are no air discharges from the process, which is under negative pressure, and the syngas is clean burning. “We know that emissions from the produced syngas when used in a gas turbine are lower than emissions from natural gas and within US EPA standards,” he said. Zenergy's next step is a feasibility study prior to provide all the costing. However, it estimates the cost of producing 1MVV of electricity would be about US$2.5 million ($2.8 million). Part of the unknown is the composition of input wastes, and that's what gives WMAA knowledge manager Mark Glover cause for concern. “The proposition by some plasma companies that I have spoken to is that they want to up the ante and take MSW and start producing energy and other reusable materials,” Glover told WME. While he loves the technology, he reckons it's not right for the waste sector. He uses the old 'garbage in, garbage out' idea. “If you put low-grade material into plasma, you will get low-grade material out at the other end, and this and other AWT technologies tend to be very sensitive to variations. MSW is a very complex material and it is very hard to control,” he said. It's not dioxins he's worried about- the ultra-high temperatures would destroy all the organic molecules that create them - but the robustness of the process.There's another worry, this one strategic. Glover says it would fail WMAA's energy from waste guidelines, which say that the material to be converted to energy would not be accepted as the best alternative to converting the MSW. It says any recover able organic fraction of the waste should be separated and turned to compost, a higher order use than energy conversion. What's more, it remains largely untested at scale, meaning considerable technological and budgetary uncertainties remain. But that won't stop Prasad from pushing the technology into Australia and it that hasn't silenced the buzz offshore. PWR is full steam ahead with plans to build a US$20 million pilot plant in Montgomery, currently undergoing a feasibility study. If successful, the Missouri city would be the first in the world to use graphite arc plasma to gasify household waste.