Isra-Mart srl: Wood chips a competing boiler fuel to lignites

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A fledgling energy resource from southern forest harvesting waste is gaining traction in Otago and Southland with a growing number of organisations installing or converting to wood-chip fired boilers.

With proposed lignite mining in the South, and its potential conversion to briquettes for boiler fuel appearing set to remain a highly contentious option, the alternative wood chip fuel source is attracting more attention.

The concept is already a popular and proven option in Europe and North America and is lauded as clean burning, with particle emissions between a third to a fifth those of coal, being a renewable source, efficient and carbon neutral.

Southern Wood Council chairman Grant Dodson said between Otago and Southland's combined more than 215,000 hectares of forest, members could produce and supply wood to support the regions' biomass requirements.

"Otago and Southland forestry is in a great position to sustainably produce and use a lot more of its own biofuel," Dodson said.

Following harvesting, wood and residues, such as branches, log ends, and lower grade pulp logs can be chipped then airdried over 12 months for use in woodchip boilers, or manufactured into pellets, to be used in pellet burners for industrial and commercial energy.

Chief executive Grant Smith of Wellington-based Energy For Industry (EFI); a subsidiary of Meridian Energy, said the Dunedin Energy Centre (owned and operated by EFI) has just finished trialling the blending and burning of lignite with woodchips; anywhere from 30% to 100% of woodchips.

"The future is looking quite positive for wood fuel in Dunedin. We want to step it to the next level," Smith said.

The trials were proving successful and Dunedin Energy was looking at using up to 8000 tonnes per year in its boilers.

Smith believed that Dunedin had the capacity to use up to 20,000 tonnes annually, as a replacement for either coal or lignite in the running of run boilers.

"Depending on the wood chip costs and volumes, it could ultimately replace all [types of] coals," Smith said.

While the low-grade lignite had been cheaper than wood chips, there are increasing costs in clean air and carbon emissions involved with its use.

"People are now looking to wood chips because of the environmental perspective," Smith said.

Since a pilot programme at Dunstan High School in 2009 replacing traditional coal systems, numerous organisations have installed wood-chip fired boilers, including Bayfield High School, Clutha Valley Primary School, the University of Otago's department of psychology building, the Little Sisters of the Poor retirement home, the Wanaka Community Pool and Invercargill-based commercial laundry McCallum Group.

Smith said wood chip operations in Christchurch had recently been expanded to make use of trees from aborists and also untreated demolition timber being amassed in Christchurch.

Dunedin City Council-owned City Forests' spokesman Kent Chalmers said 1,500 tonnes had been dried in the past for EFI clients, using mainly "leftover" short pulp logs. The company was in talks with Dunedin clients for potential supplies.

*Simon Hartley is senior business reporter for the Otago Daily Times.