Abstract
BackgroundAustralia’s energy future is at the crossroads and the role of renewable sources is in focus. Biomass from sustainably managed forests provide a significant opportunity for electricity and heat generation and production of liquid fuels. Australia has extensive native forests of which a significant proportion are on private land. However, there is limited knowledge on the potential capacity of this resource to contribute to the expansion of a biomass for bioenergy industry. In addition, there are concerns on how to reconcile biomass harvesting with environmental protection.MethodsWe used regional ecosystem vegetation mapping for Queensland to stratify harvestable forests within the 1.8 m hectares of private native forests present in the Southeast Queensland bioregion in 2014. We used a dataset of 52,620 individual tree measurements from 541 forest inventory plots collected over the last 10 years. Tree biomass was estimated using current biomass allometric equations for Australia. Biomass potentially available from selective sawlog harvesting and silvicultural treatment across the bioregion was calculated and mapped.ResultsCurrent sawlog harvesting extracts 41.4% of the standing tree biomass and a biomass for bioenergy harvest would retain on average 36% of felled tree biomass on site for the protection of environmental and fauna habitat values. The estimated area extent of harvestable private native forests in the bioregion in 2013 was 888,000 ha and estimated available biomass for bioenergy in living trees was 13.6 million tonnes (t). The spotted gum (Corymbia citriodora subsp. variegata) forests were the most extensive, covering an area of 379,823 ha and with a biomass for bioenergy yield of 14.2 t∙ha−1 (with approximately 11.2 t∙ha−1 of the biomass harvested from silvicultural thinning and 3 t∙ha−1 recovered from sawlog harvest residual).ConclusionsSilvicultural treatment of private native forests in the Southeast Queensland bioregion, has the capacity to supply a large quantity of biomass for bioenergy. The availability of a biomass for bioenergy market, and integration of sawlog harvesting and silvicultural treatment operations, could provide land owners with additional commercial incentive to improve the management of private native forests. This could potentially promote restoration of degraded forests, ecological sustainability and continued provision of wood products.
Highlights
Australia’s energy future is at the crossroads and the role of renewable sources is in focus
The mean annual rainfall for the bioregion ranges from 1000 to 2400 mm and the monthly mean maximum temperature ranges from 22.9 °C – 31.3 °C at Gladstone and monthly mean minimum temperature ranges from 8.6 °C – 19.8 °C at Springbrook in the southern end of the bioregion
Stratification of private native forests This study only used forests that are in remnant condition (forests where dominant canopy has >70% of the height and >50% of the cover relative to the undisturbed state or reference condition (Eyre et al 2015) of a native forest stand) or mapped as high value regrowth (the immediate lower category for a naturally regenerated site that is tracking towards the pre-clear vegetation structure and floristic composition and is approaching the remnant condition (Accad et al 2017))
Summary
Australia’s energy future is at the crossroads and the role of renewable sources is in focus. National assessments of potential bioenergy resources in Australia including agricultural crops and residues, native grasses, forestry (plantations, shortrotation tree crops and native forests) and organic municipal solid wastes based on statistics published by Australian Bureau of Agricultural and Resource Economics (ABARE) (Farine et al 2012; Crawford et al 2016; AREMI 2017) Among these bioenergy resources, the specific role of forests as a renewable energy source has received widespread global attention (Fung et al 2002; Janowiak and Webster 2010; Davis et al 2012; Klockow et al 2013; Meadows et al 2014; Rothe et al 2015). The need for reliable localised information on the potential role of the Australia’s expansive native forest resource in energy generation is overdue (Raison 2006; Rothe et al 2015)
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