Australian Life Cycle Assessment Society conference
The use of timber construction products and their environmental impacts is growing in Europe. This paper examines the LCA approach adopted in the European CEN/TC350 standards, which are expected to improve the comparability and availability of Environmental Product Declarations (EPDs). The embodied energy and carbon (EE and EC) of timber products is discussed quantitatively, with a case study of the Forte building illustrating the significance of End-of-Life (EoL) impacts. The relative importance of timber in the context of all construction materials is analysed using a new LCA tool, Butterfly. The tool calculates EE and EC at each life cycle stage, and results show that timber products are likely to account for the bulk of the EoL impacts for a typical UK domestic building.
The building sector is increasingly identified as being energy and carbon intensive. Although the majority of emissions are linked to energy usage during the operation part of a building's life cycle, choice of construction materials could play a significant role in reducing greenhouse gas emissions and other environmental end-point damages. Increasing the use of wood products in buildings may contribute to the solution, but their environmental impacts are difficult to assess and quantify because they depend on a variety of uncertain parameters. The present cradle-to-gate life-cycle analysis (LCA) focuses exclusively on a glued-laminated wood product (glulam) produced from North American boreal forests located in the province of Quebec, Canada. This study uses primary data to quantify the environmental impacts of all necessary stages of products' life cycle, from harvesting the primary resources, to manufacturing the transformed product into glulam. The functional unit is 1 m3 of glulam. This is the first study based on primary data pertaining to Quebec's boreal forest. Quebec's boreal glulam manufacturing was compared with two other LCAs on glulam in Europe and the United States. Our results show that Quebec's glulam has a significantly smaller environmental footprint than what is reported in the literature. From an LCA perspective, there is a significant advantage to producing glulam in Quebec, compared with the European and American contexts. The same holds true in regard to the four end-point damage categories.
This series highlights five whole building life cycle assessments (WBLCAs) of buildings incorporating the building material known as cross-laminated timber (CLT) into some or all of their structure, using a primary cradle-to-grave system boundary. This case study series will serve as an educational resource for academics, professionals, and CLT project stakeholders. While there is some uncertainty about the best way to reduce greenhouse gas emissions from architecture and construction, using CLT and other wood building materials is one possible means to reduce the emissions associated with a building’s materials. When forests are managed sustainably, wood construction materials can contribute to climate change mitigation goals as an indefinite carbon store and as a replacement of other fossil-fuel intensive materials. WBLCA is an assessment method to estimate the environmental impacts of buildings; this series offers insight into the current possibilities and limitations of WBLCA for CLT buildings. The series begins with background information on WBLCA methods and CLT, a review of previously published CLT building WBLCAs, and a life cycle assessment of an individual CLT wall element using the WBLCA softwares Tally® and Athena Impact Estimator for Buildings (Athena IE).
Life Cycle Assessment (LCA) has been used to understand the carbon and energy implications of manufacturing and using cross-laminated timber (CLT), an emerging and sustainable alternative to concrete and steel. However, previous LCAs of CLT are static analyses without considering the complex interactions between the CLT manufacturing and forest systems, which are dynamic and largely affected by the variations in forest management, CLT manufacturing, and end-of-life options. This study fills this gap by developing a dynamic life-cycle modeling framework for a cradle-to-grave CLT manufacturing system across 100 years in the Southeastern United States. The framework integrates process-based simulations of CLT manufacturing and forest growth as well as Monte Carlo simulation to address uncertainty. On 1-ha forest land basis, the net greenhouse gas (GHG) emissions ranges from -954 to -1445 metric tonne CO2 eq. for a high forest productivity scenario compared to -609 to -919 for a low forest productivity scenario. All scenarios showed significant GHG emissions from forest residues decay, demonstrating the strong need to consider forest management and their dynamic impacts in LCAs of CLT or other durable wood products (DWP). The results show that using mill residues for energy recovery has lower fossil-based GHG (59%–61% reduction) than selling residues for producing DWP, but increases the net GHG emissions due to the instantaneous release of biogenic carbon in residues. In addition, the results were converted to 1 m3 basis with a cradle-to-gate system boundary to be compared with literature. The results, 113–375 kg CO2 eq./m3 across all scenarios, were consistent with previous studies. Those findings highlight the needs of system-level management to maximize the potential benefits of CLT. This work is an attributional LCA, but the presented results lay a foundation for future consequential LCAs for specific CLT buildings or commercial forest management systems.
The study investigates the environmental benefits of reusing Cross Laminated Timber (CLT) panels. The Global Warming Potential (GWP) of a single-stored Coffee shop built in 2016 in Kobe city was calculated, considering different CLT reuse ratios, forest land-use and material substitution possibilities. The results showed that as the rate of reused CLT panel increases the total GWP decreases. Moreover, in all cases, the option with smallest GWP is when the surplus wood is used for carbon storage in the forest, revealing the importance of a growing forest for increasing the environmental benefits of timber utilisation. The results suggest the systematic reuse of CLT panels offers a possibility to increase the carbon stock of Japanese Cedar plantation forests and further mitigate the environmental impact of construction.
The Nature Conservancy is leading a multi-institution collaboration to quantify the potential for innovative mass timber materials to support improved forest management, revitalize forest economies and mitigate greenhouse gas emissions. Life cycle assessments (LCAs) of engineered timber products such as glued laminated timber (glulam) and cross-laminated timber (CLT) in construction have highlighted their environmental advantages over conventional materials such as concrete and steel. However, there is little understanding of how developing new markets for such materials could support the wood product sector and the management of US forests. This applied research will assess in detail the potential impacts of large-scale growth in mass timber demand on wood product markets, timber harvest, forest management and climate change mitigation in key wood-producing regions across the USA and globally, as well as opportunities to leverage these markets to support US forest management and rural economies. The findings will be used to produce peer-reviewed publications and design a suite of targeted stakeholder engagement materials and programs, providing an objective, credible fact base to inform the design of policies and programs to maximize environmental and economic benefits of mass timber use for the forest sector.
Katerra is a start-up construction company that has developed a vertically integrated cross-laminated timber (CLT) manufacturing supply chain and facility. Katerra commissioned the Carbon Leadership Forum (CLF) and the Center for International Trade in Forest Products (CINTRAFOR) at the University of Washington to perform a life cycle assessment (LCA) study to understand the environmental impacts and opportunities for impact reduction in Katerra’s CLT supply chain and manufacturing process. CINTRAFOR performed an LCA of the CLT supply chain and production process while the CLF performed a whole building LCA of a new building that used CLT produced at Katerra’s CLT facility.
Katerra has developed its own cross-laminated timber (CLT) manufacturing facility in Spokane Valley, Washington. This 25,100 m2 (270,000 ft2 ) factory is the largest CLT manufacturing facility in the world, and is capable of producing approximately 187,000 m3 of CLT per year. Katerra has also established a vertically integrated supply chain to provide the wood for the CLT factory. Production started in summer of 2019.
Katerra commissioned the Carbon Leadership Forum (CLF) and Center for International Trade in Forest Products (CINTRAFOR) at the University of Washington to analyze the environmental impacts of its CLT as well as the Catalyst Building in Spokane, Washington. The Catalyst is a 15,690 m2 (168,800 ft2), five-story office building that makes extensive use of CLT as a structural and design element. Jointly developed by Avista and McKinstry, Katerra largely designed and constructed the building, and used CLT produced by Katerra’s new factory. Performing a life cycle assessment (LCA) on Katerra’s CLT will allow Katerra to explore opportunities for environmental impact reduction along their supply chain and improve their CLT production efficiency. Performing an LCA on the Catalyst Building will enable Katerra to better understand life cycle environmental impacts of mass timber buildings and identify opportunities to optimize environmental performance of mid-rise CLT structures.
The goal, scope, methodology, and results of this analysis are detailed in this report.