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• Substitution factors for forest products for the Canadian context were developed. • Substitution factors ranging from 0.51 to 0.91 tC/tC were found. • They will lead to more accurate assessments of the forest GHG mitigation potential. • These factors will help governments to manage forest and fight climate change. Evaluating the climate change mitigation potential of the forest sector requires a holistic approach based on forest carbon (C) sequestration, C storage in harvested wood products (HWP) and substitution on markets. High uncertainty is associated with substitution factors, that express avoided fossil greenhouse gas (GHG) emissions from the use of forest-based products in replacement of GHG-intensive materials and fossil fuels. Few studies have focused on the development of substitution factors in Canada, resulting in the use of unrepresentative generic data. Here, we provide a framework to reduce uncertainties related to substitution factors for primary wood products in a Canadian context. A life cycle assessment framework is used to quantify fossil GHG emissions for a baseline and a wood-intensive scenario. For solid product substitution, we focused on the construction sector and analyzed a range of innovative wood buildings with steel and reinforced concrete as alternative materials. We found non-weighted averages of 0.80 tC/tC for sawnwood and 0.81 tC/tC for panels. For energy substitution, we analyzed cases with different specifications on biomass product, facility type and alternative fossil fuel source in non-residential heat production and biofuel transportation sectors. We found a non-weighted average of 0.80 tC/tC for non-residential heat production and 0.51 tC/tC for biofuel transportation, that can be interpreted as 0.91 tC/tC for heavy fuel oil, 0.69 tC/tC for light fuel oil and 0.68 tC/tC for natural gas substitution. These results provide a benchmark for substitution factors in Canada, to help guide forest management strategies for climate change mitigation. [ABSTRACT FROM AUTHOR]

The demand for wood-based energy is foreseen to grow as energy and climate policies around the world promote the use of bioenergy for climate change mitigation. However, the carbon impacts of forest bioenergy range widely in the literature. The value-choices made on the response of forest management to bioenergy demand have a major influence on the results obtained from modeling exercises and may actually change the contribution of forest bioenergy from climate worsening to climate change mitigation. Despite their relevance, there is very little information, or transparency, as to the empirical basis by which these assumptions are chosen and evaluated against. This study aims to fill in this crucial knowledge gap through a mix of critical review, analysis of historical statistical data, and expert judgement. Several prominent studies reporting climate change mitigation from forest bioenergy in three countries are reviewed: Canada, Sweden, and Southeast USA. This analysis shows that the studies rely on assumptions that bioenergy demand will spur supply responses aimed at more efficient forest management and/or relative increases in forest area. Confronting literature assumptions with trends in historical data, we present the most extensive reality-check of bioenergy literature assumptions to date. We find that studies projecting a large role of forest bioenergy in climate change mitigation rely on assumptions that are too optimistic, at times outright unrealistic. We believe scientists could avoid the misinterpretation of their results and improve the policy relevance of their work by more transparent reporting of: i) value-laden assumptions, ii) their influence on the results, iii) the process and rationale behind such assumptions, especially distinguishing between assumptions that reflect incremental changes in management from assumptions requiring transformational change in several industrial sectors. • Accounted carbon benefits of forest bioenergy depend on underlying assumptions. • Forest bioenergy mitigates climate change only when additional biomass is produced. • Forest management responses assumed in the literature are overly optimistic. • Post Normal Science tools can help scientists avoid misinterpretation of results. • Scientists should better convey that model results are contingent on value-choices. [ABSTRACT FROM AUTHOR]