Oil mallee harvested (left) a few months ago,
(middle) recently and (right) five years ago.
Image by Oil Mallee Association

Described by central Wheatbelt farmer Mike Kerkman as “God’s answer to carbon production”, the oil mallee is a carbon sink that grows rapidly, lives for many years, retains 30 per cent of its carbon in its enormous root system and continues to coppice, or resprout, after it has been harvested.

But, as the recent National Oil Mallee Conference in Perth heard, the tree could prove a one-stop troubleshooter in Western Australia’s embattled agricultural zone.

“Mallee is brilliant for rehabilitating the land,” says David McFall of the Oil Mallee Association

“Mallees have been through eons of climate change and are superbly adapted for survival. They are incredibly hardy, cope with drought and are adaptive to poor landscape positions. Their roots make them particularly good for lowering the water table in land affected by salinity and for reducing erosion.”

Planting the trees could help save millions of hectares of farming land. But the mallee’s usefulness, and its importance in an age affected by climate change and dependence on fossil fuels, does not end there.

In the past eight years, the tree has emerged as a viable feedstock for biofuel. As Associate Professor Hongwei Wu of Curtin University of Technology has discovered, mallee produces 41.7 times more energy than is used in its cultivation, providing a substantially higher return on energy investment than corn, canola and mustard.

Its success as a biofuel has been proven by Verve Energy’s $25 million pilot Integrated Wood Processing plant in Narrogin, and the company is seeking private investment to build full-scale plants.

As Verve’s renewable energy scientist Dr Don Harrison told the conference, full-scale plants, each generating 5MW (megawatts) of eco-friendly power, are a commercially viable way for regional centres to meet their energy needs.

“We still have renewable energy targets as well as carbon credits,” he said. “Growing grain for energy instead of food is not sustainable, while growing mallees for energy creates a process that is complementing agriculture instead of replacing it.”

The key to making the IWP plant profitable was producing electricity plus two by-products, eucalyptus oil and activated carbon.

Designed by new energy technology company Enecon, the plant used special fluidised beds to partially burn the mallee wood, producing charcoal. Steam activation technology then converted the charcoal to activated carbon – a product used in air and liquid purification and for which worldwide demand is growing at four per cent a year. Eucalyptus oil was then distilled from the leaves and what’s left – the “spent” leaves – were gasified to fuel the boiler.

Mr McFall says it is precisely because mallee is so versatile that an industry plan is needed to manage it.

He says that while well aware that mallee could become a valuable carbon crop in the post-Garnaut economy, the Oil Mallee Association sees its potential as far greater.

“We are looking beyond carbon credits,” he says. “Our long-term aim is to take the energy embodied in these trees and use it. Why not develop that scientific side and process it into another carbon neutral industry?”

Managed carefully, the trees could even help preserve farming communities.

“If emissions trading goes international, there is a whole world of investment out there that could buy grain production areas and use them to plant trees as carbon sinks. Farmers are going to be naturally inclined to want the biggest bang for their buck – but is signing up whole tracts of land for tree planting rather than food production in the best interests of the broader community?

“If the trees are harvested locally and we use them to create energy locally, we could see our communities becoming self-sufficient as well as creating jobs.”

Already, keen farmers have planted more than 12,000 hectares of mallee in the central Wheatbelt.

Mr McFall sees this as only the beginning: “An easy 10 per cent of our agricultural land – well over a million hectares – could be planted with mallee. You would end up with a billion trees without even scratching the surface.”

He called for government policy support and funding.

“If we can show the market that there is government support, enterprising people will pick up the mallee project and run with it.”