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Rotovegas feasts on crude flush

In August last year an innovative Kiwi technology used to breakdown waste was given a booster by the Government in the form of $1 million in funding. And yesterday, the pilot plant for the technology was officially opened for business, ready to test the innovative process that converts biosolid waste (sewage sludge) into valuable chemical products. 

The thermal oxidation pilot plant has been installed at Rotorua District Council’s Wastewater Treatment Plant as part of a research project involving Crown Research Institute Scion and Rotorua District Council, who joined forces in 2008 to develop a new approach to the management of organic waste.  

“Switching on the pilot plant is a hugely exciting step for all of us involved in this project. Soon we’ll be able to really see how well the technology can work outside the laboratory,” says Scion chief executive Dr Warren Parker. 

Developed by Scion, the pilot plant is an initiative of the Waste 2 Gold biosolids research programme into organic waste utilisation. So how exactly will waste be converted into a valuable by-product? The pilot plant uses thermal deconstruction to “cook” the biosolids and break them down into re-useable chemicals and a range of other by products. These can be used for fertilisers or in the production of bioplastics and biofuels. 

The purpose of the pilot plant is to trial the process at a level that will provide sufficient data to determine if the technology could work at a full commercial scale. After operating for an initial 12 months and, depending on results, the next stage will be to construct a demonstration plant, sized to handle all of the biosolids from Rotorua’s Wastewater Treatment Plant. 

Rotorua District Council chief executive Peter Guerin says that if the pilot is successful, it could prevent thousands of tonnes of biosolid waste going to landfill per year, something he says could “ultimately achieve net benefits (in terms of cost reduction and value creation) of around $4 million per year for the council and community. This really brings the concept of “Waste 2 Gold” to life with significant benefits for ratepayers and the environment”. 

It’s certainly not all about the environment and the Rotorua District Council acknowledges the technology has the potential to provide a revenue source from the converted waste. Rotorua has approximately 8,500 tonnes of biosolid waste going to landfill every year at a current cost of approximately $920,000. This project has the potential to further reduce all organic waste going to landfill. 

The technology has applications beyond sewage biosolids. Scion says research shows that the same technology could also be used for managing organic wastes from food and industrial processors. 

“The growing waste streams from expanding industries such as pulp and paper, agriculture, dairy, meat and fruit processing represent a tremendous potential resource for New Zealand that can be tapped into by environmental technologies like those developed through the Waste 2 Gold biosolids research programme,” says Parker. “Also, greenhouse gas emissions and the risk of contaminating leachates arising from organic wastes will be substantially reduced.” 

And for all of those interested in the ins and outs of the technology, here’s a few key pints, as stated by Scion: 

* The technology is based on a deconstruction process that uses biological and thermo-chemical stages to convert organic wastes into re-useable products and reduce their environmental effects.

* Acetic acid production: commercial ethanol is currently used to improve the sewage treatment system's ability to remove nitrogen. The acetic acid produced through Scion’s process could replace this ethanol, with potential savings up to $632,000 per year.

* Energy generation: the process is essentially a "wet combustion" and will generate excess heat for use in the deconstruction plant and elsewhere at the site. In addition, methane can be generated at several stages in the system for electricity production.

* Environmental improvements: significant greenhouse gas reductions ( more than 70 percent) will be achieved through deconstruction. In addition, quantities of high nutrient content leachates produced at the landfill will be considerably reduced.

* The deconstruction stage leads to a 30-fold decrease in biosolids volumes - meaning a potential saving in the order of $920,000 per year in transportation, landfill fees and waste levies.