Friday, December 8, 2023

Huntly wood trial hailed as leap ahead for biofuel

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Early promise of possible solution to the forest slash issue.
Huntly power station offers an opportunity to have a single large user of wood pellets to underpin the wood fuel market for NZ, says Brian Cox of Bioenergy Association of NZ.
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A recent successful trial of wood fuel to fire Huntly power station has spun the market on its axis, say biofuel boosters, providing a large industrial user capable of underpinning New Zealand’s emerging biofuel sector.

With this could come a solution to the forest slash issue bedevilling the industry.

Genesis Energy has just completed a successful trial using 1000t of charcoal-like “torrefied” wood fuel pellets to fire its boilers at Huntly power station. 

The power company sourced pelletised wood fuel from a Canadian supplier to replace traditional coal, crushing them and introducing the material to the boilers as it would for coal. 

Genesis partnered with Fonterra to trial the charcoal-like wood pellets, with the two companies representing the largest processors in New Zealand seeking to move from coal-fired boiler use.

Genesis interim CEO Tracey Hickman said after the week-long trial that the fuel may not prove to be the silver bullet to replace coal, but the company is compelled to explore biomass options.

Brian Cox, executive officer of the Bioenergy Association of NZ, said the trial’s success, and any large-scale uptake of the pellets by the  two companies of the pellets, signals a move from a supply-based to a demand-driven market dynamic. 

“Suddenly forest owners can see that demand could be steady, and large,” Cox said.

Estimates on potential demand from Genesis are that Huntly would require on average of 5 petajoules (PJ) of biomass energy a year. 

Available wood residue in NZ is estimated at 50-150PJ, with availability depending upon access and economics.

To source that energy from forests alone would require about 22,500ha to create 250,000t of black pellets.

Having a biofuel option for Huntly would retain an invaluable energy backstop that, although important for providing power over dry years, is now problematic when its coal-fired emissions are considered. 

Having a sustainable  biofuel option could push the  station’s life out at least another  decade, possibly two.

Meantime Fonterra is on a pathway to “de-coal” its boilers by 2037, with only six of its 29 plants remaining coal-fired by the start of the next dairy season.

“They are having to move fast, and are doing one to two a year, and this is being met with a good response from the biofuel industry,” Cox said. 

Estimates are that a wholesale move to wood fuel by Fonterra would require about 77,000ha of forest for sourcing low-grade logs as an energy source.

Cox’s own estimates are that a quarter of the low-grade logs currently exported would be enough to fuel Huntly.

“We do not have to grow a heap of new trees to do this. Diverting a log from low-grade export gives you better yield if it is used for wood fuel, as you use it all, not just a set length of it. It’s 100% usable.”

He said there is no doubt this is already happening with low-grade logs in the South Island, and he expects it to become far more common in coming years.

Forest Owners’ Association technical manager Glen Mackie told Farmers Weekly while the news at Huntly is encouraging, research on making such pellets in New Zealand remains relatively new.

“I am not sure we have a good handle yet on how far a torrefied wood pellet can be transported economically. There is a rail head at Wairoa, and Huntly is on the main trunk line. 

“It could be the Industry Transformation Plan is the vehicle for getting a plant off the ground on the east coast.” 

Eastland Wood Council CEO Philip Hope said members have for some time been investigating new initiatives to help solve both the slash issue and meet NZ’s biodiversity goals.

“A wood-pellet processing facility is one option some of our members have put forward, which may form part of the solution to the woody debris issue. 

“However, there are some limitations including the amount of material that may be required, issues with transportation to market, and the cost to set it up.”

Scion researchers are also working on prototype wood pelletising technology that can be deployed in forests to convert the slash into useful wood fuel pellets. 

A project in the central North Island is due to test the technology on site in coming months.

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