An expert in waste-to-energy technology doubts a proposal to turn rubbish made in Manawatū into various products will actually work.

He also says the people behind it contradict themselves and are using misleading terms while wrongly claiming the process creates renewable energy.

A hearing about Bioplant NZ’s plan to build a pyrolysis plant in Feilding is due to start on Tuesday.

Bioplant has applied to Horizons Regional Council for resource consents it needs to do air discharges from the plant, which the company says will turn rubbish into diesel, electricity and charcoal.

According to the Ministry for the Environment, pyrolysis involves heating waste without exposure to oxygen, which then produces gas, liquid and solids.

READ MORE: * Air quality experts say Manawatū pyrolysis plant will have almost no impact * Manawatū waste-to-fuel plant touted as way to turn rubbish into energy * Feilding pyrolysis plant consent process to be publicly notified * Concerns over Bioplant's resource consent for waste-to-energy plant * Scientists doubt pyrolysis plant is as green as marketing suggests

Bioplant has said the plant is based on existing technology being used in other countries without any problems, but opponents are against it due to fears about its potential environmental impact.

Witness statements from experts have been made public as part of the consent process, including one from pyrolysis expert Dr Andrew Rollinson, who has written about, researched and operated pyrolysis systems.

He has also assessed plants of various types in Europe, Australia, North America and the Middle East, as well as advised the United Nations on the topic.

He said Bioplant’s proposal had multiple discrepancies, contradictions and “a generally high amount of disorder”.

Pyrolysis could not operate by creating its own fuel, as Bioplant has said it would, as it had high energy demands, Rollinson said.

“Pyrolysis consumes energy rather than provides it.”

Pyrolysis had been used for millennia to turn wood in charcoal, but that was very different to pyrolysis of rubbish, he said.

He was also critical of terms used by Bioplant to describe the by-products of pyrolysis.

Bioplant described the diesel as biodiesel, but Rollinson said biodiesel was made from vegetable fatty acids.

The diesel Bioplant would make came from plastics, essentially turning fossil fuels into diesel, which would be burned and create greenhouse gas emissions, he said.

“The fossil fuels have merely spent a period of their lifecycle as a plastic product.”

Bioplant called the charcoal, which would be made by its proposed plant, “biochar”, but Rollinson said biochar was the process of using char for soil remediation.

It would be irresponsible to suggest using Bioplant’s char in such a way, since such char was a repository for toxins and heavy metals, Rollinson said.

He was also critical of Bioplant’s name, saying it was misleading because there was no biological process involved in its proposed pyrolysis.

The hearing into Bioplant’s consents starts on Tuesday at 9am at Manfeild Park Stadium.