**7. Environmental Biomass Potential**

The environmental biomass potential, more particularly the displaced GHG, and net GHG mitigation were assessed by Farine et al. (2012) who used forest inventory reports and literature conversion factors. This study calculated the emission (the equivalent of CO2) associated with the various pathways from feedstock to bioenergy by summing the emissions related to production, transport, conversion, and combustion in Australia. Several scenarios of using forest biomass and the role of forest in GHG mitigation in Australia are reviewed [82] and implemented in a New South Wales case study [77]. The New South Wales case study used a carbon accounting model to estimate the greenhouse gas balance in a comparison between a timber-production and a conservation scenario. Modelling considered emissions resulting from the establishment and managemen<sup>t</sup> of forests, harvesting, transport to the mill, manufacturing, transport to consumer and disposal. The research also compared results with emissions from the manufacture of non-wood products and the use of fossil energy. No specifics of the models' calculation are provided, and most of the emission factors are retrieved from a life cycle inventory report from Australia [83].

The SimaPro LCA model used by England et al. (2013) was combined with survey data on emissions and the Australasia Ecoinvent database and incorporated emissions from burning fossil fuel, non-CO2, fire, establishment, management, harvest, haulage, transport, and fertiliser. A sensitivity analysis was used to assess the influence of varying parameters and assumptions on carbon emission and tested in a ±20% range. No details on the LCA model and calculations are provided.

Cowie and Gardner (2007) performed a comparative study on the use of sawmill residues for the generation of electricity and the manufacture of particleboard using emission equations. Calculations of GHG emissions included those associated with harvesting, collecting, chipping transport, processing at the mill, evaporation of moisture, and re-establishment of the plantation [79]. The study uses a reference fossil fuel scenario to calculate the net emission reductions from the two alternative bioenergy scenarios. In comparison, they excluded al common factors between the reference and case scenarios. For the bioenergy cases, the avoided emission is calculated considering the variation in carbon emission per unit primary energy and the variation in the efficiency of combustion. Emission of CO2 that are avoided are calculated as the mathematical product of CO2 equivalent in the biomass utilized and a "displacement factor" (DF), where:

$$DF = \frac{\text{efficiency of bienergy system}}{\text{efficiency of lossil system}} \times \frac{\text{CO}\_2 \text{ emission per J lossil fuel}}{\text{CO}\_2 \text{ emission per J biomass}}.\tag{2}$$

Emissions of CO2 as a result of biomass combustion are excluded based on biomass production from a sustainably harvested plantation.
