From: Jessica Maddock, Communications Unit

Date: 27 January 2009

Christchurch's energy reuse initiative progresses

The Christchurch City Council is applying for consent to use a mix of renewable energy sources to run the new biosolids drying facility.

Water and Waste Operations and Maintenance Manager Mike Bourke says the Council is seeking resource consent from Environment Canterbury to use untreated wood, at times supplemented by landfill gas, to run the drying facility which is planned for the Christchurch Wastewater Treatment Plant (CWTP)

"We've chosen wood because it's clean, renewable and there's a plentiful local supply.

"The wood burning process won't emit any smoke or odours," says Mr Bourke.

The drying facility, for which the construction contract is expected to be let shortly, will dry dewatered biosolids so they can be used to rehabilitate land, such as mines, or as a fertiliser. At present the biosolids are used to rehabilitate the Burwood Landfill.

The drying facility will be part of the Council's innovative energy reuse programme, which at present involves recovering landfill gas from the closed Burwood Landfill and piping it to QEII to provide electricity and heat the water at the recreation centre.

This project has earned the Council $4 million in carbon credits, which will fund the 28 initiatives in the Council's Sustainable Energy Strategy for Christchurch 2008-18. The first initiative to be implemented, subsidised building consents for solar water heating systems, was launched late last year.

The landfill gas project also won the sustainability and clean technology category of the 2008 New Zealand Engineering Excellence Awards.

An extension to the pipe is underway to take landfill gas from QEII to the city centre, via the CWTP, to heat, cool and power the Christchurch Art Gallery and the new Christchurch Civic Building in Hereford Street.

"We're working hard to finish the pipeline because, at the moment, the Burwood Landfill's producing about 1000 cubic metres of landfill gas per hour, but we're typically only using around 300 cubic metres at QEII. Ratepayers will save about $2.3 million a year in energy costs when this project's finished," says Mr Bourke.

The Council already has consent to use landfill gas to run the drying facility, however, another energy source was required when it was decided to instead use the landfill gas to run the art gallery and civic building. The current consent also allows biodiesel to be used to run the drying facility, as a backup in case there is a problem with the pipeline.

Mr Bourke said the new consent seeks permission to use both wood and, at times, an increased amount of landfill gas to run the drying facility.

"We want flexibility because energy demands at the art gallery and civic building fluctuate. This way we could use the excess landfill gas to run the drying facility, when it's not being used elsewhere. This would save flaring it and save wood."

About 20% more landfill gas will be required to run the drying facility than the current consent provides for, as it was obtained before the type of drying facility was selected.

Biogas generated by the CWTP is also being reused. Biogas is produced by the bacteria which breaks down the biosolids and is used to run gas engines which generate electricity to run the CWTP and supply the national grid.

The amount of biogas produced increases with population growth and it will be piped through the existing pipe network to power QEII, the art gallery and the civic building when the landfill gas runs out in 15 to 20 years.

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