The Huntly power station replaced planet-heating coal with wood in a trial to bring down the facility’s large carbon footprint. In a busy year, the plant can import more than a million tonnes of coal to feed the national grid. Owner Genesis Energy has pledged to significantly reduce its annual greenhouse emissions, and believed wood transformed into pellets could replace coal, the highest-emitting fossil fuel.
Although shipped from Canada, the wood pellets have a footprint at least 90% lower than coal, Genesis said. The trial demonstrated Huntly’s power generating units can successfully run on 100% wood.The Waikato-based power plant produces roughly 6% of the country’s total carbon dioxide each year. When its coal usage rises – as it did in 2021 – Huntly sways New Zealand’s carbon footprint.
But although Huntly’s workers spent a year preparing for the trial, it involved a single Rankine power unit burning wood for several hours, Genesis confirmed. The test is unlikely to reduce the company’s annual carbon footprint by much.
The black pellets are a dried, concentrated form of wood energy – producing far less carbon than coal. However, Genesis is looking for a long-term, local source of wood pellets or “biomass”, said interim chief executive Tracey Hickman in a statement.
“It’s worth some focus by government and business to see if a sustainable local supply chain can be developed. Compared to some other decarbonisation solutions, biomass conversion could be implemented much sooner to the benefit of the country.” With a reliable supply of pellets, Hickman said, Huntly could become a lower-carbon source of back-up electricity generation for another decade – or even longer.
“Eventually, new technology or an over-supply of new renewable generation might be able to provide security of supply, but that is some time away and not yet certain.” Genesis said biomass factories can take 18 months to build. By next year, the company – partnering with Fonterra – hoped to determine whether a local supply of wood pellets was a feasible option. Genesis had secured enough coal to last through to 2024, under normal circumstances.
According to Scion researchers, there is enough waste or residual wood from forests to replace all the fossil fuels burned in domestic industrial boilers.
To create black pellets, wood is heated slowly without oxygen as high as 300C. This process (known as “torrefaction”) dries the material and concentrates the energy. While the pellets contain a similar amount of energy to coal, Huntly had to use roughly 25% more wood to achieve the same amount of electricity generation.