Comparative Life-Cycle Assessment of a High-Rise Mass Timber Building with an Equivalent Reinforced Concrete Alternative Using the Athena Impact Estimator for Buildings
The goal of this study was to update life-cycle assessment (LCA) data associated with laminated veneer lumber (LVL) production in the Pacific Northwest (PNW) region of the United States from cradle-to-gate mill output. The authors collected primary mill data from LVL production facilities per Consortium on Research for Renewable Industrial Materials (CORRIM) Research Guidelines. Comparative assertions were not a goal of this study.
The goal of the present study was to develop life-cycle impact assessment (LCIA) data associated with gate-to-gate laminated veneer lumber (LVL) production in the southeast (SE) region of the U.S. with the ultimate aim of constructing an updated cradle-to-gate mill output life-cycle assessment (LCA). The authors collected primary (survey) mill data from LVL production facilities per Consortium on Research for Renewable Industrial Materials (CORRIM) Research Guidelines. Comparative assertions were not a goal of the present study.
Environmental Life-Cycle Assessment and Life-Cycle Cost Analysis of a High-Rise Mass Timber Building: A Case Study in Pacific Northwestern United States
Global construction industry has a huge influence on world primary energy consumption, spending, and greenhouse gas (GHGs) emissions. To better understand these factors for mass timber construction, this work quantified the life cycle environmental and economic performances of a high-rise mass timber building in U.S. Pacific Northwest region through the use of life-cycle assessment (LCA) and life-cycle cost analysis (LCCA). Using the TRACI impact category method, the cradle-to-grave LCA results showed better environmental performances for the mass timber building relative to conventional concrete building, with 3153 kg CO2-eq per m2 floor area compared to 3203 CO2-eq per m2 floor area, respectively. Over 90% of GHGs emissions occur at the operational stage with a 60-year study period. The end-of-life recycling of mass timber could provide carbon offset of 364 kg CO2-eq per m2 floor that lowers the GHG emissions of the mass timber building to a total 12% lower GHGs emissions than concrete building. The LCCA results showed that mass timber building had total life cycle cost of $3976 per m2 floor area that was 9.6% higher than concrete building, driven mainly by upfront construction costs related to the mass timber material. Uncertainty analysis of mass timber product pricing provided a pathway for builders to make mass timber buildings cost competitive. The integration of LCA and LCCA on mass timber building study can contribute more information to the decision makers such as building developers and policymakers.
With the world’s increasing focus on sustainability in the construction sector through green building systems, the U.S. Department of Agriculture (USDA) has been actively engaged in green building advocacy in the United States through USDA Tall Wood Building competitions and follow-up research on use of mass timber for nonresidential buildings. The USDA Forest Service, Forest Product Laboratory (FPL) funded the study of environmental performance of the pioneer mass timber building (the John W. Olver Design Building) built at University of Massachusetts Amherst in 2016. The Athena Sustainable Materials Institute conducted the whole building life cycle assessment (LCA) using the Impact Estimator for Building software. Secondly, the reported LCA results led to development of an environmental building declaration (EBD) in conformance with European standard EN 15978. Environmental building declarations summarize the embodied and operational environmental impacts during the full building life cycle. An EBD is much like an environmental product declaration (EPD) which is intended for marketing and educational use, but instead of covering individual products like an EPD, an EBD covers the whole building. Lastly, the LCA results of the Design Building were then compared with a functionally equivalent steel and concrete building to acquire the whole building LCA credit in Leadership in Energy and Environmental Design (LEED) v.4 for green buildings. With the mass timber use in the Design Building, the building qualified for the whole building LCA credit in LEED v4. With this project, FPL is helping to standardize environmental performance reporting and advanced mass timber building sustainability.
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.
The 58th International Convention of Society of Wood Science and Technology
Research Status
Complete
Notes
June 7-12, 2015, Grand Teton National Park, Jackson, Wyoming, USA
Summary
Documenting the environmental performance of building products is becoming increasingly common. Developing environmental product declarations (EPDs) based on life-cycle assessment (LCA) data is one way to provide scientific documentation. Many U.S. structural wood products have LCA-based “eco-labels” using the ISO standard. However, the standard requires underlying life-cycle inventory (LCI) data to be of recent age. This study updates the gate-to-gate manufacturing LCI data for laminated veneer lumber (LVL) for Pacific Northwestern (PNW) and for southeastern (SE) United States. Modeling the primary industry data per 1.0 m3 of LVL through LCI analysis provides the inputs and outputs from veneer logs to LVL starting at the forest landing. For PNW and SE, cumulative mass-allocated energy consumption associated with manufacturing 1.0 m3 of LVL was found to be 5.64 and 6.87 GJ/m3, respectively, with about 25% of the primary energy derived from wood residues. Emission data produced through modeling found that estimated biomass and fossil CO2 emissions in kg/m3 were 127 and 139 for the PNW and 108 and 169 for the SE. One m3 (~535 OD kg wood potion) of LVL stores about 980 kg CO2 equivalents. The amount of carbon stored in LVL thus exceeds total CO2 emissions during manufacturing by about 350%. This study provides the necessary gate-to-gate LVL manufacturing LCI data for the cradle-to-gate LCA to develop an updated EPD.
The primary outcome of this work is to provide integrated analysis of the environmental, financial, and social benefits and costs of using CLT in tall wood buildings. Secondary outcomes will be (1) information, including a design team checkoff that can be used to inform the building community as they make decisions on specific, new building projects, and (2) an informational foundation for these stakeholders and others to begin to evaluate the complex tradeoffs between, and optimization of, environmental, financial, and social benefits and costs.
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