Turning waste plastic into energy

POET Systems is using anaerobic digestion to turn plastic into energy The South Australian company expects to have its first two machines — each capable of processing 20 tonnes of plastic a week — operating commercially in about 12 months.

The plastic-to-energy technology has been designed to be applied to polyethylene, polypropylene, polystyrene and expanded polystyrene. South Australian inventor David Thompson said the anaerobic digestion process varied upon disposal feedstock and depended also upon temperature and system set-up.

“The POET system prepares waste plastic in a way that microbial digestion can take place quickly, and I think that’s really the key to making it a commercial opportunity,” Thompson said.

The first two machines will be built at wastewater treatment plants in regional areas of Victoria.

The same microbes will treat the plastic and the water simultaneously. The microbes then die and leave behind liquid and solid biomass, which can be used as fertiliser, and biogas, which can be separated into methane and carbon dioxide.

Thompson, who is based in Adelaide, said the methane could be used to create heat and energy, possibly to power the wastewater plant, while there was also potential for the carbon dioxide to be captured and re-used.

“So basically the plastics go into an anaerobic situation in wastewater where the microbes digest the plastic and create energy,” he said.

Thompson said the system did not impact on existing recycling practices as it targeted plastics destined for landfill and would add a new revenue stream for companies in the waste industry.

“We’ve had a look at a number of scenarios, and where it actually works as a business model is at a starting point of 20 tonnes a week."

POET Systems is a 2017 semifinalist in the Australian Technologies Competition. Winners will be announced at technology showcases in Melbourne and Sydney in October and November.

Image credit: ©iStockphoto.com/Huguette Roe

This is a modified version of a story published by The Lead South Australia under CC BY 4.0