System analysis and life cycle assessment of forest supply chains with integrated biomass production

摘要

Forests are essential suppliers of raw materials for industrial products and renewable energy, which can help mitigate climate change. In Europe, the market for forest bioenergy and other wood products is expected to continue growing in the future. Therefore, new procurement methods and assortments with high energy efficiencies and low greenhouse gas (GHG) emissions are required from a climate change perspective. One alternative to current conventional supply chains is utilizing integrated supply chains where residual forest biomass is harvested and transported together with stemwood. Additionally, mobile production systems, such as small-scale mobile pellet plants that are situated close to the raw material source, could increase the efficiency of residual forest biomass supply chains, especially in regions with long transportation distances to industry. The overall aim of this thesis was to assess the cost, energy use, GHG emissions and other relevant environmental impacts (terrestrial acidification, marine and fresh water eutrophication, photochemical oxidant formation and fossil fuel depletion) of conventional and integrated forest supply chains in Northern Sweden to provide knowledge that could stimulate the development of more efficient supply chains. The assessment included modelling of conventional and integrated forest supply chains in Northern Sweden, a case study in Western Canada, and modelling of a mobile production system for pelletizing logging residues. A life cycle assessment approach was used in the analyses.ududThe results showed that integrated supply chains have the potential to reduce the supply cost for non-stemwood assortments. Furthermore, the integrated supply chains were more energy efficient than conventional supply chains, and have the potential to reduce GHG emissions by approximately 13%. The reduction in terrestrial acidification, marine and fresh water eutrophication, photochemical oxidant formation, and fossil fuel depletion associated with switching from a conventional to integrated supply chain was 17%, 24%, 17%, 17%, and 13%, respectively. The evaluated Swedish supply chains also showed, on average, better environmental profiles per oven dry tonne than the Canadian supply chains that were assessed. The environmental performance of a small-scale mobile pellet production system operating at forest landing and at forest terminal was similar in both alternatives. However, if the terminal had access to the power grid, then the environmental impacts (with the exception of fresh water eutrophication potential) decreased, and operating at the terminal became a better option from a life cycle assessment perspective.