Rows of mallee eucalypts near Narrogin, WA

Integrated Mallee Processing

Enecon is instrumental in the development of a unique, new industry in Western Australia. This industry provides a commercial incentive for the development of plantation eucalypts for land care, via the production of activated carbon, renewable energy and eucalyptus oil from trees. Enecon is part of a team that includes Verve Energy, formerly Western Power Corporation, Department of Conservation and Land Management (CALM), the Oil Mallee Company and CSIRO.

• The low rainfall zone of Western Australia faces severe salt degradation unless current agricultural practice changes. Extensive planting of mallee eucalypt trees in parallel with ongoing farming is proposed as one method to manage water usage and salinity.
• The planting of mallee trees for environmental benefits will be greatly increased if the trees also have a separate commercial return. The eucalyptus oil market has been considered as one part of such a commercial driver. This has been enhanced by Enecon via the concept of Integrated Tree Processing. A new industry is now being developed to make tree planting commercial via the integrated processing of the whole mallee trees to produce activated carbon from the wood in parallel with eucalyptus oil from the leaves. Renewable electricity is also produced via combustion or gasification of the biomass.
• It is felt that such an industry in Western Australia has the long term potential to utilise more than one million tonnes of sustainable green biomass per year. This will provide a massive boost to tree planting for salinity control, as well as generating renewable energy, sales of activated carbon, charcoal and oil, and hundreds of new jobs in rural areas.
• Renewable electricity generated by this industry in the longer term could be as much as 50 MW. Substantial additional Greenhouse benefits come from carbon sequestering in the permanent root systems of the mallee trees.

Introduction

The large scale planting of oil mallee in Western Australia is being actively promoted by the WA Department of Conservation and Land Management (CALM) as a key strategy in the reduction of potentially catastrophic salinity problems in Western Australia's low rainfall zone. Much of the WA wheatbelt is in this zone and is already showing salt damage. CALM predicts that salt damage could mean that up to 30% of this 20 million hectare zone will be lost to productive agriculture in the next few decades if nothing is done. Tree planting in parallel with annual cropping is one method of managing the water table and thereby the salt problem. After some years of testing, CALM has selected the mallee eucalypt as the most suitable "tree crop" for this role in the wheatbelt, where low rainfall makes other trees such as blue gum uneconomical. Planting of mallee has commenced, with many million trees in the ground, and several hundred participating farmers have formed a mallee growers group and an independent company (Oil Mallee Company - OMC) to further their interests. The achievements to date by CALM, the growers and OMC reflect years of hard work and many millions of dollars invested in research and tree planting.

Integrated activated carbon, electricity and eucalyptus oil plant completed in 2006. The plant will allow commercial sales of each product as well as the development of data for the design and operation of subsequent plants. The potential for this new industry is significant - multiple plants in dryland agricultural areas providing a range of environmental and community benefits.

An important reason for the selection of mallee was its commercial potential. Mallee produces eucalyptus oil that already has markets in the fragrances and pharmaceuticals industries. In the longer term it is hoped that economies of scale in production will also allow the oil to be marketed as a solvent degreaser, a natural alternative to banned halogenated hydrocarbon solvents, such as trichloroethane, that damage the ozone layer.

Independent of the work by CALM, CSIRO Forestry and Forest Products has for some years been developing processes for energy recovery and the manufacture of charcoal and activated carbon products from wood. These processes have been developed initially at the laboratory scale and more recently at a pilot plant constructed by CSIRO in Victoria. Preliminary product trials of activated carbon produced have shown it to perform very well when compared with commercial carbons.

The CSIRO technology was licensed to Enecon Pty Ltd in 1998. Discussions with CALM commenced in 1998 and have lead to an understanding of the particular benefits of utilising the CSIRO technology with the mallee industry. These benefits are described in more detail below.

Integrated Tree Processing

Production of eucalyptus oil alone only utilises the leaves of the mallee trees. To better utilise the whole tree an Integrated Tree Processing (ITP) plant has been proposed by Enecon. Such plants would be located in mallee growing areas and operate as follows:

1. Coppiced mallee trees are mechanically harvested and the whole tree is transported to the processing plant.
2. The wood and the leaves are separated.
3. The leaves are crushed and the oil is extracted via distillation (using steam from the wood processing).
4. The wood is carbonised to charcoal. The combustion of volatiles in the wood during this stage releases much of the energy in the wood as heat, which may in turn be used to raise steam.
5. The charcoal may be sold, or processed further and then activated with steam to produce activated carbon. During the activation step most of the energy remaining in the wood is released as water gas, which may be used for heat, steam or as a fuel for a gas engine or turbine.