Forest residues for renewable carbon in the Australian bioeconomy

Leanda Garvie

doi:10.25907/00789

Research Highlights: This research assesses the potential for forest residues to replace non-renewable carbon and thereby contribute to a sustainable bioeconomy in Australia. An assessment was made of environmental benefits, specifically reduced carbon emissions, and economic feasibility in terms of supply chain costs – both critical to the design of, and investment in, forest biomass supply projects in Australian plantations. The research suggests forest residue bioenergy is a viable alternative to traditional energy sources, offering substantive emission reductions. Cost drivers and efficiencies in the forest biomass supply pathways were identified, providing valuable insights for designers and investors in forest-based bioeconomies. Background and Objectives: Concerns about greenhouse gas emissions and climate change have led to a shift in attention away from fossil fuel-based energy sources in favour of renewables. Bioenergy is a renewable energy generated from biomass. Forests hold most of the world’s biomass and are an important source of renewable carbon including bioenergy. Bioenergy, and other bio-based products, can be produced from both forest residues (from harvesting or maintenance activities) and mill residues (from timber processing activities). Sustainably sourced forest residues as a feedstock for energy is well established in some parts of the developed world, particularly Europe, but is a relatively new and under-utilised energy source in Australia. Building better knowledge of environmental and economic sustainability aspects of utilising forest residues is important for development of this emerging industry in Australia. The objective of this research, therefore, was to assess emission savings, supply chain costs and efficiencies, and support needs for forest residues as a source of renewable carbon (as opposed to non-renewable, fossil fuel-based carbon) and contributor to the emerging bioeconomy. Materials and Methods: To demonstrate potential emission savings of substituting fossil fuels with forest residue bioenergy, the national carbon accounting model for calculating and reporting greenhouse gas emissions (FullCAM) was applied to a case study in Queensland, Australia. For the economic feasibility part of the research, a systematic survey methodology, based on the Delphi application, was employed to evaluate relative costs in the Australian forest biomass supply chain compared with an established market, the European Union (EU). Finally, to identify optimal pathways for delivering forest residues to markets, a consultative process followed by an analytic hierarchy process (AHP) was undertaken. Results: The energy pathway with the greatest emission offsets is biomass-fed combined heat and power replacing coal-fired electricity. From 4.5 to 7.3 tonnes of carbon dioxide equivalents per hectare per year (tCO2-e ha−1 year−1) could be saved. Overall, forest biomass supply costs were generally lower in Australia than in the EU for all residue types other than stumps, while transportation costs were found to be equal or higher than the EU. Extraction costs were ranked the highest, followed by processing (chipping), transporting, and handling (moving biomass to a vehicle). Costs to store biomass were ranked the lowest. The most efficient way to deliver forest residues to the market was identified to be chipping biomass in the field. Conclusions: Forest residues can generate emission savings when replacing traditional fossil fuels, demonstrating the contribution they can make towards a lowcarbon economy and achieving climate change mitigation goals. Costs of supplying forest biomass in Australia are generally in the direction of equal to or lower than respective costs in the EU, but there are nevertheless some drivers of supply chain costs, as well as efficiencies that are likely to influence the design and success of the forest residue market. Environmental and economic sustainability indicators suggest good potential for forest residues to play a role in the emerging bioeconomy in Australia.

Forest residues for renewable carbon in the Australian bioeconomy

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