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Energy & Fuels 2009, 23, 3290–3299
Mallee Biomass as a Key Bioenergy Source in Western Australia: Importance of Biomass Supply Chain Yun Yu,† John Bartle,‡ Chun-Zhu Li,† and Hongwei Wu*,† Curtin Centre for AdVanced Energy Science and Engineering, Department of Chemical Engineering, Curtin UniVersity of Technology, GPO Box U1987, Perth WA 6845, Australia and ReVegetation Systems Unit, Natural Resources Branch, Nature ConserVation DiVision, Department of EnVironment and ConserVation, Locked Bag 104 Bentley DeliVery Centre 6983, Western Australia ReceiVed February 5, 2009. ReVised Manuscript ReceiVed April 4, 2009
The competitiveness of biomass as a source of energy supply strongly depends on biomass supply chain. This paper presents a discrete mathematical model of mallee biomass production, harvest, on-farm haulage, and road transport to a central bioenergy plant. The model has been specially designed to assess the performance of mallee biomass production in the “wheatbelt” agriculture area of Western Australia (WA). It is based on a continuous, integrated, and streamlined supply chain from farm to the bioenergy plant and evaluations based on the road systems in the same region. The delivered cost of mallee biomass strongly depends on feedstock collection distance, farm size (a surrogate for on-farm haulage distance), road transport scenario, and proportion of the land planted to mallee. The results indicate that although the mallee biomass in WA is planted in a well-ordered distribution through alley farming, it is clear that transport, including on-farm haulage and road transport, can make significant contributions to the total cost of mallee biomass delivered to a bioenergy plant. For the same distance, biomass on-farm haulage is considerably more expensive than biomass road transport, and its cost increases substantially with farm size. For small plants requiring short feedstock collection distances, on-farm haulage cost dominates the total biomass transport cost. The importance of biomass road transport increases with the feedstock collection distance (i.e., plant capacity). Long-distance biomass road transport is not feasible, and a mallee-based bioenergy plant will still be constrained in scale and most likely located in regional centers. Strategies for reducing the delivered cost of mallee biomass include (a) locating the biomass processing plant near areas of high planting density; (b) managing or upgrading on-farm tracks and roads, planning seasonal schedules, or improving haulage efficiency to minimize on-farm haulage cost; and (c) integrating road transport into the business of either biomass growers or biomass processing plant owners, rather than that of independent third parties as transport service providers because separate ownership leads to increased cost.
1. Introduction Biomass is becoming an increasingly important part of the global response to the challenges of energy security, greenhouse gas emissions, and climate change. Although it is not a complete solution, it can play an important role in partial substitution of fossil fuel in energy supply.1 Utilization of biomass resources is constrained by its widely dispersed occurrence, low-energy density, and seasonality of supply. These factors make collection, transport, and storage operations complex and expensive.2 The overall system economics and energy performance may be strongly influenced by the supply chain from farm to the bioenergy plant. For example, a recent EU case study showed that supply chain coordination can be a barrier to implementation of bioenergy systems, although such barriers are dynamic and depend on the context.3 In a Canadian case study of corn stover * Corresponding author. E-mail:
[email protected]; phone: +61-892667592; fax: +61-8-92662681. † Curtin University of Technology. ‡ Department of Environment and Conservation. (1) Patterson, T. Energy Fuels 2008, 22, 3506. (2) Caputo, A. C.; Palumbo, M.; Pelagagge, P. M.; Scacchia, F. Biomass Bioenergy 2005, 28, 35. (3) McCormick, K.; Kåberger, T. Biomass Bioenergy 2007, 31, 443.
as a feedstock for ethanol production, Kumar et al.4 indicated that truck delivery arrangements could be a scale-limiting factor. Hence it is important for supply chain logistics to be adapted to biomass supply characteristics. This requires careful supply chain analysis and design, as well as technological innovation, to achieve best performance.5 In Western Australia (WA) mallee eucalypts are being developed to be profitable woody crops for the low to medium rainfall (300-600 mm mean annual rainfall) “wheatbelt” agricultural area.6,7 As part of this development some 14 000 ha have been established across the WA wheatbelt since the early 1990s.7,8 This development aims to use profitable woody crops as the vehicle to also achieve important environmental improvements within the present agricultural system, in particular, to help control the long-standing problem of dryland (4) Kumar, A.; Cameron, J. B.; Flynn, P. C. Bioresour. Technol. 2005, 96, 819. (5) Turkenburg, W. Renewable energy technologies. In World Energy Assessment: Energy and the Challenge of Sustainability s An OVerView; Goldemberg J. Ed.; United Nations Development Program: New York, 2000. (6) Bartle, J.; Cooper, D.; Olsen, G.; Carslake, J. ConserV. Sci. West. Aust. 2002, 4, 96. (7) Cooper, D.; Olsen, G.; Bartle, J. Aust. J. Exp. Agric. 2005, 45, 1369. (8) Bartle, J.; Olsen, G.; Cooper, D.; Hobbs, T. Int. J. Global Energy Issues 2007, 27, 115.
10.1021/ef900103g CCC: $40.75 2009 American Chemical Society Published on Web 05/04/2009
Mallee Biomass As a Key Bioenergy Source in WA
Figure 1. Alley farming of mallee in agricultural land under the threat of dryland salinity at Kalannie, Western Australia (courtesy from the Oil Mallee Company of Australia). Mallee trees are planted in the form of long narrow belts and conventional annual crops are planted between the mallee belts.
salinity;9 to provide shade, shelter, amenity, and erosion control; to achieve better protection of biodiversity; and as a means of carbon sequestration. At the time of writing this paper, these environmental benefits have no direct economic value to producers and hence are less tangible than crop production and would otherwise be difficult to achieve. Mallees are multistemmed native eucalypt low tree or shrub species that can be used as short-cycle coppice crops similar to willow and poplar grown in the northern hemisphere.10 Mallee species are well adapted to warm temperate winter rainfall climates where evaporation may greatly exceed rainfall for much of the year. They are deep rooted and sprout or coppice freely after harvest. The harvest cycle can be as short as 3 years. In WA alone, the extensive adoption of mallee in the wheatbelt could potentially supply ∼10 million dry tons of biomass per year8 and provide the feedstock to sustain large-scale industries. Additionally, mallee can only be successfully cultivated on a small proportion of the land in order to be able to gain access to enough extra water (i.e., water in addition to the rainfall falling on the planted area) to achieve commercial yields. In the wheatbelt this will usually be
