ForestHWP – a new approach to the assessment of the carbon cycle in native forests managed for multiple use

Australian climate change policy has largely overlooked the potential role of forestry in mitigating climate change. When determining the climate impacts of any industry sector, it is important to adopt a true life cycle assessment approach that takes into account all relevant carbon emissions and removals. 

As a consequence, this research, funded by FWPA, assessed the true balance of greenhouse gases (GHG) emitted and stored in native forests managed for both production and conservation in NSW and Victoria. It considered all the key elements of the carbon cycle in forests and in harvested wood products (HWPs, including carbon stored in HWPs in landfills and product substitution impacts (for HWP and use of biomass for bioenergy). There was generally a clear substitution benefit by using hardwood products from the study sites compared to alternatives. For example, use of hardwoods from unsustainably managed tropical forests results in emissions 20 times greater than for the use of hardwood from the study sites. Use of steel or concrete poles instead of hardwood poles results in emissions 10 times greater than for the use of hardwood from the study sites. The calculated product substitution impact for pulp production from silvertop ash and mountain ash was on average 218 and 1200 t C/ha, respectively. Ignoring this impact would majorly underestimate the current GHG balance of native forestry in those regions.

The research which included field work across a range of species and sites also introduced a new model, ForestHWP, a tool designed to capture all key elements of the GHG balance in forests and HWP. ForestHWP allows immediate integration of parameters and running of simulations of repeated disturbance events such as forest harvest or fire. In addition to GHG implications, the study considered the socio-economic implications of native forest management which are often ignored in GHG balance studies of native forestry.

The key conclusion of the research is that the relative differences in the GHG balance of production and conservation scenarios do not warrant policies halting native forest management for wood production. When industry value-added benefits and carbon abatement benefits were added together, the production management scenarios generated much higher GHG mitigation values than the conservation management scenarios. This result was independent of the carbon price (low, medium or high).

There is considerable room, however, for improvement in the GHG outcomes of managing for production. These opportunities could be realised in the forest, in the processing of wood products and in diverting materials to different uses at the end of the life of HWPs. The project demonstrated that one way to enhance the GHG outcomes of production forestry is via the increased use of biomass for bioenergy. Currently the majority of forest harvest residues are burnt or decay over time, with no GHG benefit. For example, the study highlighted that for regrowth blackbutt forests, for each hectare of forest harvested, an estimated 150 tonnes of biomass in harvest residues (“pulp-grade”) and mill residues is currently available for use. Increased use of forest and sawmill residues for renewable energy generation typically displaces the use of fossil fuels, resulting in a net GHG benefit.

Project Report PNC285-1112

FWPA will be hosting an on-line presentation by the researcher, Fabiano Ximenes (NSW – DPI), on the conclusions of this project on Wednesday 17 February at 11:00am (AEDT). Subscribe to webinar invitation.