Life Cycle Assessment of North American Laminated Strand Lumber (LSL) Production

Abstract

Raw materials for buildings and construction account for more than 35% of global primary energy use and nearly 40% of energy-related CO2 emissions. The Intergovernmental Panel on Climate Change (IPCC) emphasized the drastic reduction in GHG emissions and thus, wood products with very low or negative carbon footprint materials can play an important role. In this study, a cradle-to-grave life cycle assessment (LCA) approach was followed to quantify the environmental impacts of laminated strand lumber (LSL). The inventory data represented North American LSL production in terms of input materials, including wood and resin, electricity and fuel use, and production facility emissions for the 2019 production year. The contribution of cradle-to-gate life cycle stages was substantial (>70%) towards the total (cradle-to-grave) environmental impacts of LSL. The cradle-to-gate LCA results per m³ LSL were estimated to be 275 kg CO2 eq global warming, 39.5 kg O3eq smog formation, 1.7 kg SO2 eq acidification, 0.2 kg N eq eutrophication, and 598 MJ fossil fuel depletion. Resin production as a part of resource extraction contributed 124 kg CO2 eq (45%). The most relevant unit processes in their decreasing contribution to their cradle-to-grave GW impacts were resource extraction, end-of-life (EoL), transportation (resources and product), and LSL manufacturing. Results of sensitivity analysis showed that the use of adhesive, consumption of electricity, and transport distance had the greatest influences on the LCA results. Considering the whole life cycle of the LSL, the final product stored 1,010 kg CO2 eq/m³ of LSL, roughly two times more greenhouse gas emissions over than what was released (493 kg CO2 eq/m³ of LSL) from cradle-to-grave. Overall, LSL has a negative GW impact and acts as a carbon sink if used in the construction sector. The study results are intended to be important for future studies, including waste disposal and recycling strategies to optimize environmental trade-offs.

Emerging Engineered Wood for Building Applications

“…215 This study shows that adhesive usage has a large influence on seven out of nine impact indicators and concludes that "ensuring the optimal adhesive use" can efficiently improve the overall environmental performance. 215 Hence, using parametric LCA to explore and quantify the impacts of different options can support process optimization toward a sustainable direction.…”

“…LCA has been widely employed to quantify the life cycle environmental impacts of traditional engineered wood products, including glulam, I-joist, laminated strand lumber (LSL), LVL, oriented strand board (OSB), plywood, composite board, and other wood products. ,,,,,− These studies have used LCA to identify the major contributors to environmental performance. These contributors can be either life cycle stages (e.g., forest operations, panel production, use phase) or processes (e.g., chipping, heat generation, resin application, sawing) .…”

“…The sensitivity analysis demonstrates that changing the mass allocation method to the economic allocation method increase the results by 16–28%; increasing the use of methylene diphenyl diisocyanate resin and using no phenol formaldehyde resin enlarges the nonrenewable energy consumption but leads to small effects on the total environmental impacts . Khatri et al deployed sensitivity analysis to investigate the environmental consequences of changing adhesive resin usage, electricity, wood fuel, and transportation distance in LSL manufacturing . This study shows that adhesive usage has a large influence on seven out of nine impact indicators and concludes that “ensuring the optimal adhesive use” can efficiently improve the overall environmental performance .…”

“…Khatri et al deployed sensitivity analysis to investigate the environmental consequences of changing adhesive resin usage, electricity, wood fuel, and transportation distance in LSL manufacturing . This study shows that adhesive usage has a large influence on seven out of nine impact indicators and concludes that “ensuring the optimal adhesive use” can efficiently improve the overall environmental performance . Hence, using parametric LCA to explore and quantify the impacts of different options can support process optimization toward a sustainable direction.…”

“…The scope definition needs an explicit description of the subject to be studied (e.g., an engineered wood product), functional unit, system boundary, data requirements, impact categories selected, and other scope definition items. , Previous LCAs of engineered wood products commonly select product-level units as their functional units (e.g., 1 m 3 of wood product, 1000 board feet of wood product). Among those, 1 m 3 of engineered wood products is the most adopted in previous literature. − Other product-level functional units are related to specific constructional applications (e.g., 1 m 2 of the roof, 30 m 2 of surface decking) to compare with traditional building materials (e.g., steel). − For example, Petersen and Solberg used 1 m 2 roof as the functional unit to compare the life-cycle energy consumption and greenhouse gas (GHG) emissions of glulam and steel . Besides, stand-level functional units (e.g., 1 ha forest land) can be used to incorporate the effects of forest management strategies and forest yield into the LCA of wood products …”