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Attributional and consequential life cycle assessment of wood chip and bark mulch use on Okanagan apple orchards, including uncertainty assessment and best practices recommendations

University of British Columbia

Food systems contribute substantially to environmental impacts, including 19-29% of greenhouse gas (GHG) emissions. The use of wood and bark chip mulch as soil cover has been proposed to reduce GHG emissions, in addition to water use and herbicide use on apple orchards. The current study expanded the scope of this prior investigation of mulch use to include all “upstream” processes for the production and transportation of the mulch used on orchards, as well as all other industrial systems that use mulch and would be impacted (i.e. through decreased availability) if mulch use on orchards were to increase. This was done using life cycle assessment (LCA), a sustainability management tool that accounts for all environmental inputs and outputs along the supply chain, or life cycle, of a product. The differences in water and herbicide use with and without mulch were not accounted for due to the experimental study design. When the orchard life cycle was considered, apples produced using mulch had higher GHG emissions than those without mulch, as well as higher impacts in all of the other impact categories considered (including acidification, eutrophication, toxicity, land and energy use). When the systems that would likely be affected by an increase in mulch use were also considered (i.e. bioenergy co-generation and paper production, the primary alternative uses of bark and wood chips in the region), the results were mixed. Some impact categories showed a benefit for mulch use on orchards and some showed a negative impact. These results also depended on whether the co-generation processes were assumed to take place in British Columbia or Washington (locations where biomass is used for co-generation). These results do not support the recommendation of mulch application on orchards as a sustainability management practice, based on the GHG mitigation benefits alone (other mulch benefits were not included). This study also demonstrates the importance of including LCA in sustainability assessment, and highlights the need for improved availability of high quality data for LCA in Canada in order to reduce uncertainty and improve the robustness of results.

Text

2019-12-07

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/72586

Biology

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/