Advanced Materials’ Life Cycle Assessments: LCA of Alternative Binders for Engineered Wood Products

Abstract

Engineered wood products EWPs, seldom assess the off-site incorporation of glues, epoxy resins and binders. To address this gap, a life-cycle assessment (LCA via SimaPro) of four adhesives is presented: melamine-urea-formaldehyde (MUF); polyurethane (PUR); a hybrid PUR-Soy adhesive; and, an adhesive-free dowel-laminated timber (DLT) system. The functional unit of the amount of adhesive required for 1m³ of cross-laminated-timber CLT is adopted within a cradle-to-gate scope. Environmental impacts are quantified across the key indicators of: global warming potential; eutrophication; ozone depletion; and, fossil fuel depletion. Results are normalised and aggregated using a weighted eco-point framework informed by Western Australian practitioner feedback. Supplementary modelling provided by XLam extended the analysis, evaluating the influence of adhesives on end-of-life scenarios such as recycling, energy recovery, landfill and reuse. Results show that MUF exhibited the lowest eco-point score overall despite the partial organic material substitution in PUR-Soy; however, findings show that adhesives contribute only 1.7-2.2% of the environmental burden of a whole CLT product representing a negligible impact. Despite this relatively minor contribution during the off-site production phase, further cradle-to-cradle analysis revealed that end-of-life EoL disposal pathways have a critical influence on the overall environmental scores of the CLT products, with over 200% variation depending on the scenario chosen. If adhesives are found to directly restrict viable disposal options, then they will play a much more critical role in determining the environmental impacts of engineered wood products. This work recommends continued innovation in bio-based and mechanical bonding systems and development of specific legislation for the disposal of EWPs with regard to adhesive contents, to allow a clearer understanding of the full impacts of these advanced materials.