Innovative technology piloted at Rotorua

31 May 2011

Today the Minister for the Environment Hon Dr Nick Smith opened a pilot plant that will test an innovative process that converts biosolid waste into valuable chemical products.

Opening of the pilot plant, installed at Rotorua District Council’s Wastewater Treatment Plant, is a milestone event in a research project involving Crown Research Institute Scion and the Council, who joined forces in 2008 to develop a new approach to the management of organic waste.

The thermal oxidation pilot plant has been developed by Scion as an initiative of the “Waste 2 Gold” biosolids research programme into organic waste utilisation.

Scion’s Chief Executive Dr Warren Parker says the new process could revolutionise the way sewage biosolids are managed.

“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”, he says.

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. The pilot plant uses thermal deconstruction to “cook” the biosolids (sewage sludge) 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.

“If successful, a full-scale plant in Rotorua could initially remove thousands of tonnes of biosolid waste going to landfill per year, and ultimately achieve net benefits (in terms of cost reduction and value creation) of around $4 million per year for the council and community,” says Rotorua District Council Chief Executive Peter Guerin. “This really brings the concept of “Waste 2 Gold” to life with significant benefits for ratepayers and the environment.”

The pilot plant will initially operate for 12 months. Depending on the 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 sees the potential of the technology to not only improve its waste disposal processes but 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.

Rotorua is a good model for many cities in New Zealand who face the same challenges regarding the disposal of biosolids and other municipal wastes. The technology can be implemented in other urban centres to reduce the volumes of biosolid going to landfills by up to 30-fold.

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.

“Also, greenhouse gas emissions and the risk of contaminating leachates arising from organic wastes will be substantially reduced,” says Dr Parker.

The technology was originally developed through a programme funded by the
Foundation for Research, Science and Technology (now the Ministry of Science and Innovation). Last August the Ministry for the Environment committed to an investment of up to $1 million over two years under its Waste Minimisation Fund to support further development of the technology.

About thermal deconstruction

Scion’s innovative technology provides a sustainable solution to the disposal of solid organic wastes. It 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. The council, the community and the environment should benefit from:
  • 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 (>70%) 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.

Scion’s approach differs from others in this field in that it controls the deconstruction process to yield useful chemicals for downstream uses, rather than complete breakdown to CO2 and water. Likely early implementers of the technology include local councils and waste management companies.

Other possible customers for the technology include (1) industrial organic waste producers (e.g. primary industries), who are looking for reduced disposal costs and alternative use options; and (2) chemical companies that may want to generate and recover chemical intermediates from the waste stream as replacements for fossil fuel-derived equivalents.

The pilot plant was built in Hamilton by Longveld Engineering, and the technical specification was prepared by Rotorua based consulting engineers Allan Estcourt Limited.