Recycling wood waste into fuel

The Ripper, developed by SCS Ltd, Christchurch, is a solid waste wood shredder/grinder and screening plant in one compact unit. The machine reduces wood waste to hog fuel (boiler fuel), an energy resource which is claimed to be economically and environmentally more beneficial than burning coal and oil.

Tokoroa Company Central Wood Recyclers uses the Ripper to clear and process waste wood from forest clear-fell, or skid sites, for Carter Holt Harvey (CHH). CWR developed a waste wood recovery business two years ago to assist CHH in a field trial to produce alternative fuel for its Kinleith Pulp & Paper plant. The processed wood is trucked to Carter Holt's Kinleith Mill where it is used as an economical alternative fuel.

The Hog fuel is burned in the company's CoGen boiler to produce steam for use in the mill. An embedded steam turbine also produces electricity for the plant.

The trial has demonstrated the quality of the product and, with further refinements to the overall process, the company is confident this will continue to be an economical alternative to other fuels.

The excess wood is a resource that has, up until now, been left behind. Up to 4% of felled wood is being left in and around skid sites. Removing the excess wood also decreases the risk of environmental damage from slips, fires and leaching into the water table.

A total of 319,000 tonnes of biomass was burned as fuel at Kinleith. The 50,000 tonne contribution from the forest residue trial was the equivalent of 1475 tonnes of displaced carbon from natural gas.

SCS managing director, Brian Court likens the Ripper to a "giant, very robust, kitchen whiz", with its swale cutting pattern able to handle large volumes of material.

"The machine is capable of screening, shredding and grinding many materials other machines cannot handle into a size and form that is easy to transport.

"The Ripper was primarily designed as a wood grinder, but is also a useful niche in the waste and recycling industries in a continually growing global market," says Court.