Tree plantations can be a source of fuel wood - wood or woodwaste - for electricity generation or methanol production.
Fuelwood can be a greenhouse neutral, renewable energy source - the wood used to produce biofuels or to generate electricity.
Mallee and other eucalypts are suitable for fuelwood plantations. They are native to Australia, can be grown in lower rainfall areas, and grow rapidly in higher rainfall areas.
Establishing fuelwood plantations on land cleared for other uses can benefit biodiversity, if the plantations include a variety of local habitat species. But will have a negative impact on biodiversity if they replace old-growth habitats.
Bio-Energy Plantations - Potential
Biomass Beckoning. Australian Energy News. Issue 7. 1998.3
CSIRO trials of intensively managed, short rotation bioenergy plantations grown on effluent, saline water and sludge at Wagga, demonstrate potentially very short rotation times of 2-3 years for fuel production. Growth rates for selected eucalypts were shown to be very high, around 15 tonnes per hectare per annum.
900,000 hectares of ex-grazing lands planted with fast growing eucalyptus species, (that is less than 2 per cent of the area currently sown to pasture crops annually), could sequester some 600 million tonnes of CO2 per annum equating to a 10 per cent reduction in greenhouse gas emissions from Australia. While up to two thirds of that CO2 would be released when the timber was eventually harvested, if the wood wastes were turned into electricity then other more carbon-intensive means of electricity production would have been avoided, significant timber resources developed and harvested, in the process locking up some CO2, and the sale of electricity would greatly improve the economics of that timber production.
Wood waste is available in large quantities and could produce electricity for less than the cost of coal fired electricity. Wood residues could be delivered to industrial boilers for $0.25c/MJcompared with black and brown coal at between $0.27-$0.29c/MJ.
The Federal Government's co-operative plan with the National Association for Forestry Industries, 'Plantations - 2020 Vision', is intended to result in a tripling of Australia's plantation estate by 2020.
Farm Forestry in Low Rainfall Areas
Onwood 28. 2000.Autumn
Growing interest in farm forestry on crop and grazing land in the 400600 mm rainfall region of southern Australia has prompted a cooperative national effort to select and breed better trees.
The Australian Low Rainfall Tree Improvement Group (ALRTIG)will concentrate on species that have grown well in trials and plantations across dryland southern Australia, and can give high value products. Hardwoods chosen for attention are spotted gums (Corymbia species), river red gum (Eucalyptus camaldulensis) and its hybrids, red ironbark (E. tricarpa and E. sideroxylon), swamp yate (E. occidentalis) and sugar gum (E. cladocalyx). The targeted softwoods are maritime pine (Pinus pinaster) and brutian pine (P. brutia).
Fuelwood Plantations for Methanol
30 Million Trees for Car Fuel, Greenhouse Cuts. CSIRO. 2000.8.16
Australians could be travelling in vehicles powered by methanol produced from plantations of trees that cover 30 million hectares of our croplands and high rainfall pasture zones within the next 50 years.
Methanol would be produced from the 'biomass' of forests growing under a 20-year rotation at a rate of 20 cubic metres a year. Plantations would need to be established at the rate of 400,000 hectares a year costing about $2,500 a hectare. The cost of a biomass electricity plant would be about one and half times the cost of a traditional electricity plant on a megawatt basis.
Fuelwood Plantations for Ethanol
Wood for Alcohol Fuels - Using farm forestry for bioenergy. Enecon Pty Ltd, Rural Industries Research & Development Corporation, May 2003
Plantation forestry with pine and eucalypts such as blue gum is well established in coastal regions with high rainfall, but is not suited to the dryer inland regions of Australia with rainfall of 600 mm or below. If commercial forestry is to be developed in these regions it will benefit from new industries that are based on the use of tree species particularly suited to the regions, for example the mallee eucalypts that grow in much of dryland Australia. Of many potential new industries, one that is receiving particular interest is the production of renewable biofuels from wood. These include the alcohols ethanol and methanol for use as liquid transport fuels. The potential market for these fuels in Australia is considerable, with the projected liquid fuel usage within 20 years estimated to be 35,000 Ml/a. An Australian liquid fuels industry using biomass for feed would be a driver for tree planting on a massive scale.
Fuelwood Plantations for Firewood
Sustainability of the Firewood Harvest
Preferred firewood species such as box, ironbark, and red gum accumulate biomass extremely slowly.
Biomass accumulation in box-ironbark forests of Victoria declines from less than 2 tonnes/hectare in young forest to virtually no net biomass production in 60 year old forest.
Mallee biomass production remains stable as the trees age, at less than 1 tonne/hectare/year. In contrast to these low rainfall forests, mean annual biomass increment in 60 year old mountain, coastal and foothill forests varies from 6 to 10 tonnes/hectare.
Fuelwood Plantations - Mallee
Eucalyptus biomass fuels: Price competitive or way off the money? (PDF). Martin van Bueren and David Vincent
Ethanol produced from mallee eucalypts grown in low rainfall areas of Western Australia would not be price competitive with petrol, even after considering environmental benefits associated with biomass fuels.
However the cost of electricity generated from this biomass would be on a par with conventional power, when carbon sequestration benefits are taken into account.
Details about Mallee Plantations in Low Rainfall Areas
The trees are grown in belts and harvested every three to four years. After harvest the trees regrow (or coppice) from the stump. Agricultural production (crops or pasture) can be practiced on the land in between the belts of trees.
A 10 metre wide mallee belt consists of trees planted 1.5 metres apart in 4 rows spaced 2 metres apart with a 2 metre buffer is allowed at each side of the belt to minimise competition between the trees and adjacent pasture or cropland. Hence around 2650 trees per hectare.
Assuming a yield of 15 kg of green biomass per tree and a 95 per cent tree survival rate, 1 hectare (1 km * 10 m) of belt will produce 37.8 tonnes of biomass. Trees are harvested once every three years, so annual average yield is 12.6 tonnes per hectare of belt.
Thus, 120,000 hectares of mallee belt, or 700,000 hectares of mixed use land (10 metre wide belts separated by 50 metre wide alleys) would produce 1.5 million green tonnes of feedstock per year.
1.5 million green tonnes of biomass per year would supply an ethanol plant with a processing capacity of 200 million litres (ML) per year or a power plant generating 150 mega watts (MW).
Tree establishment costs $1270 per hectare of belt. Maintenance costs of $8 per hectare of belt. The opportunity cost of converting agricultural land to trees is assumed to be $40 per hectare, phased down to $20 per hectare over a 20 year period due to the effects of salinity. Total biomass production over a 20 year period (6 harvests) from a hectare of land converted to tree cropping is 12.6 tonnes. Total on-farm production costs amount to $23.00 per tonne in net present value terms averaged over a 20 year timeframe.
Single row harvest operation at a harvesting speed of 5 kilometres per hour with 33 per cent downtime. Harvesting cost of $23 per tonne at each operation, which includes a bin transfer cost of $2 per tonne. Transport costs of $4 per tonne based on an average haul distance of 50 kilometres. Total harvesting and transport costs, in net present value terms averaged across the 20 year timeframe, amount to $13 per tonne.
The flow of costs over a 20 year period are consolidated and converted to a present value using a 6.5 per cent discount rate. This value is then expressed as an average cost per tonne of biomass produced over 20 years.
Fuelwood Plantations - Mallee
Integrated Tree Processing of Mallee Eucalypts. Enecon P/L for RIRDC. 2001.11
This study has analysed the economic potential for an integrated tree processing plant in Western Australia, taking coppiced, chipped mallee biomass as feed and producing activated carbon, renewable energy and eucalyptus oil as products.
Conclusion: the proposed ITP plant is financially viable, offering commercial returns to plant investors while based on adequate prices to justify planting, harvesting and transporting mallee trees.
Chipped mallee biomass can be delivered to the factory gate for $28 - $40 per green tonne. This cost includes an opportunity cost to the farmers for the land planted to mallees and also harvest and transport costs. It thus reflects what is considered to be a sufficient commercial incentive to the farmers to stimulate large scale planting needed to support Integrated Tree Processing (ITP) plants. Pricing does not include revenue from land care benefits or from carbon sequestration.
Fuelwood Plantations - Mallee
Oil Mallee Must Look to Multi-Product Industries. Don Coopera, John Bartlea, Steven Schilizzib, David Pannellb
The Western Australian salinity action plan identified woody perennial crops as a key measure to reduce the impact of agricultural salinity. In Western Australia secondary salinity threatens to reduce agricultural yields on one third of the agricultural land, cause the extinction of 450 species, damage infrastructure such as towns and roads, and lead to further degradation of rivers through increased salinity and flooding.
Oil mallees, various species of eucalypt chosen for high leaf cineole concentration and coppicing habit, are being developed in Western Australia as a potential woody perennial crop in the lower rainfall agricultural regions (550mm average annual rainfall) of southern Australia. Initial development concentrated on eucalyptus oil as the product but the economic return from residues would probably be necessary to achieve commercial viability. More recently, multi-product industries have dominated the development of oil mallees.
Integrated mallee processing - the concurrent production of eucalyptus oil, electricity and activated carbon from mallee feedstocks - could be commercially viable.
Eucalyptus oil is extracted from the leaves, activated carbon is produced from the woody material, and electricity is generated using energy released in activated carbon production and from burning residues.
Western Power Corporation will finance a demonstration scale integrated mallee processing plant at Narrogin, Western Australia during 2001. This plant will produce 210 tonnes of eucalyptus oil, 7.5 GWh of electricity and 690 tonnes of activated carbon annually from 20,000 green tonnes of oil mallees.
Upon the successful completion of testing, it is envisaged that up to nine full scale IMP plants will be built in the low to medium rainfall agricultural region of south western Australia. Each full-scale plant will be five times the size of the pilot plant.
Key parameters for the integrated mallee production plant
Feed* consumed: 100,000 t/y
Feed composition: 40% wood, 25% bark and twig, 35% leaf.
Feed cost: $30/t
Capital cost: $28.4 million over two years
Annual operational expenditure: $7.9 million
Plant life: 15 years
Activated carbon products:
GAC: 2,720 t/y @ $3000/t ex works
CAWP: 1,090 t/y @ $3000/t ex works
PAC: 294 t/y @ $1000/t ex works
Product licensing: 3% of activated carbon sales
Eucalyptus oil: 1,050 t/y @ $2000/t ex works
Electricity for export: 5 MWe "green" electricity at $60/MWh, 8000 h/y
* Feed for the plant is the whole of the mallee above ground biomass chipped and is measured in green tonnes.
Key agricultural parameters
Oil mallee establishment cost: $0.56 per mallee or $1494/ha
Land opportunity cost: $65/ha/year
Mallee maintenance cost: $10/ha/year
Mallee survival rate: 95%
Mallee productivity per harvest: 15kg/mallee
High productivity harvest regime: First harvest at 4 years, subsequently every 2 years
Medium productivity harvest regime: First harvest at 5 years, subsequently every 3 years
Harvest speed: 5 km/h
Harvester cost: $225/h
Harvest transfer cost: $2/t
Transport cost: $4.84/t
Fuelwood Plantations - Mallee
Essential oils and solvents
Recently, oil mallee has been the focus of considerable development and investment as a potential crop in Western Australia. A key product from the crop is cineole, one of the essential oils produced from a range of plants around the world. The production of cineole is attractive because it is a high-value product. However, the world market for the oil is currently about 4,000 tonnes, only four times the expected production from just one of the proposed integrated processing plants, using 100,000 green tonnes of biomass per year, being established in Western Australia. The existing cineole market is dominated by oil extracted from Eucalyptus globulus leaves in China for low-volume, high-value uses in pharmaceuticals, perfumery and foods. Therefore the oil mallee industry is seeking large lower-value markets for the oil. Attention is currently focused on using cineole to replace solvents such as trichloroethane, which has a world market size of 1,000,000 tonnes per year.
Research in this area is at an early stage and no firm conclusions can be drawn as yet. Trichloroethane has been banned in some countries because of its negative impact on the ozone layer, similar to CFCs. Eucalyptus oil is also being investigated as a competitor to limonene in the hand cleaner market, which is a world market of 20,000 tonnes per annum.
Fuel Plantations - Mallee
How Do We Manage Nitrogen in Mallee soils? (PDF). Jeff Baldock. CSIRO
In regions where potential production is defined by the availability of water (rainfall plus stored soil water) it is essential to have sufficient Nitrogen available to the crop to maximise production. Targeting higher yields and applying appropriate amounts of fertiliser N is more profitable than alternative conservative systems targeting lower yields and lower fertiliser inputs.