Case studies

New technology is turning sludge from waste water into valuable bio-fuel with environmental and financial benefits for a Southland meat processing plant.

It's a bubbling fluidised bed boiler, well-proven overseas for its ability to handle low quality fuels. The 8.5MW unit was installed at Silver Fern Farms' Finegand plant by Energy For Industry under a build, own, operate agreement.

Ernslaw Bio-Energy's new mobile wood chipper means the Central Otago company is well-placed to take advantage of an expected increase in the use of wood-chip boilers.

The company bought the $250,000 German-made Heizohack HM10-500 KT chipper and the John Deere 7530 tractor which powers it in 2008 with the help of a business grant from the Energy Efficiency and Conservation Authority.

In May 2008 Cashmere High School switched from coal to renewable wood energy to heat its site.

The new boilers produce around five times less particulate emissions than a typical school coal boiler. Carbon emissions have reduced by 216 tonnes per year. The wood-fired system is also 14% more efficient.

"There used to be soot and ash in the gutters. Now we just have clean, clean emissions," says Cashmere High support services manager Roger O'Regan.

Waste was one of the first considerations for Southern Pine Products when it started manufacturing MDF (medium density fibreboard) products.

The company opted to install a briquette press, which turns MDF dust into combustible briquettes for boiler fuel.

Moffatts Flower Company, a greenhouse complex only 5 km from Southern Pine, now buys all the briquettes the company produces.

The saving in Southern Pine's waste disposal costs is projected to be $180,000 a year and annual revenue from briquettes is projected to be around $25,000.