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.
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.
As the state of Oregon begins to introduce a new cap and trade program to reduce the effects of its greenhouse gas emissions, the state has opted not to incorporate its largest greenhouse gas emitter; the timber industry. The decline of the timber industry after the 1980’s had lasting effects on disadvantaged communities, and state politicians have battled the cap and trade bill in fear of further deterioration of the timber industry. In this paper I aim to take an in depth look at the potential that CLT has in Oregon, how it can be promoted by the government, and what the environmental effects of it are. I found that, with the rise of mass timber construction and promotion of green building, the state has the opportunity to use revenues from its cap and trade program to economically incentivize CLT construction that can provide relief to economically stressed rural logging communities, all whole bolstering its efforts to better the environmental impact of an ever expanding construction industry.
With advances in wood product development and building code acceptance, mass timber structural systems have become viable alternatives to steel and concrete structural systems (Post 2015). These mass timber systems have environmental benefits, such as carbon sequestration ability and lower greenhouse gas emissions than steel and concrete systems. How can mass timber materials such as cross-laminated timber (CLT) reduce the environmental impacts of buildings, and how certain is this reduction? In order to truly answer this question, environmental impact assessments of CLT and other wood materials must first address variation and uncertainty in forest management and biogenic carbon accounting.
Most office building construction relies on steel and concrete for mid-high rise office building applications. The primary goal of this thesis is to understand the implications of CLT and mass timber construction systems for mid-high rise office buildings in Seattle by developing a prototypical office building located on a specific site. This research thesis will focus on comparing this prototypical mass timber office building design to the same/similar design using industry standard construction materials for Seattle. The criteria for comparison will include code, cost, schedule and greenhouse gas emissions.