Manufacturing of building materials and construction of buildings make up 11% of the global greenhouse gas emission by sector. Mass timber construction has the potential to reduce greenhouse gas emissions by moving wood into buildings with designs that have traditionally been dominated by steel and concrete. The environmental impacts of mass timber buildings were compared against those of functionally equivalent conventional buildings. Three pairs of buildings were designed for the Pacific Northwest, Northeast and Southeast regions in the United States to conform to mass timber building types with 8, 12, or 18 stories. Conventional buildings constructed with concrete and steel were designed for comparisons with the mass timber buildings. Over all regions and building heights, the mass timber buildings exhibited a reduction in the embodied carbon varying between 22% and 50% compared to the concrete buildings. Embodied carbon per unit of area increased with building height as the quantity of concrete, metals, and other nonrenewable materials increased. Total embodied energy to produce, transport, and construct A1–A5 materials was higher in all mass timber buildings compared to equivalent concrete. Further research is needed to predict the long-term carbon emissions and carbon mitigation potential of mass timber buildings to conventional building materials.
As part of the CORRIM Phase I research, this study completed a full gate-to-gate life-cycle inventory for the production of glued-laminated timbers (glulam) produced in two regions of the United States—the Pacific Northwest (PNW) and Southeast (SE). Data collected from surveys of manufacturers are presented for energy requirements, raw materials use, and emissions to land, water, and air allocated for one cubic meter and 1000 cubic feet of glulam. The glulam manufacturers surveyed represented 70 and 43% of the region's total glulam production for the PNW and SE, respectively. From both regions, 82% of the raw material and energy inputs and emission outputs were allocated to the glulam product, leaving the remaining 18% allocated to co-products. Contributions to the glulam process included impacts for the inputs of lumber and adhesives. Results show that wood drying and adhesive manufacturing make major environmental contributions to the glulam process. In addition, fuel sources, either biomass or fossilbased, have significantly different emission impacts to the environment. Wood fuel representing wood waste and hogged fuel accounted for nearly 50% of the cumulative energy consumed, while for wood fuel used for heat energy to dry lumber represented 65% and 100% for the PNW and SE glulam models. The cumulative energy from all fuel types including wood fuel allocated for one cubic meter of glulam was 6,748 MJ/m3 when manufactured in the PNW and 7,213 MJ/m3 when manufactured in the SE.
While high-rise mass-timber construction is booming worldwide as a more sustainable alternative to mainstream cement and steel, in South America, there are still many gaps to overcome regarding sourcing, design, and environmental performance. The aim of this study was to assess the carbon emission footprint of using mass-timber products to build a mid-rise low-energy residential building in central Chile (CCL). The design presented at a solar decathlon contest in Santiago was assessed through lifecycle analysis (LCA) and compared to an equivalent mainstream concrete building. Greenhouse gas emissions, expressed as global warming potential (GWP), from cradle-to-usage over a 50-year life span, were lower for the timber design, with 131 kg CO2 eq/m2 of floor area (compared to 353 kg CO2 eq/m2) and a biogenic carbon storage of 447 tons of CO2 eq/m2 based on sustainable forestry practices. From cradle-to-construction, the embodied emissions of the mass-timber building were 42% lower (101 kg CO2 eq/m2) than those of the equivalent concrete building (167 kg CO2 eq/m2). The embodied energy of the mass-timber building was 37% higher than that of its equivalent concrete building and its envelope design helped reduce space-conditioning emissions by as much as 83%, from 187 kg CO2 eq/m2 as estimated for the equivalent concrete building to 31 kg CO2 eq/m2 50-yr. Overall, provided that further efforts are made to address residual energy end-uses and end-of-life waste management options, the use of mass-timber products offers a promising potential in CCL for delivering zero carbon residential multistory buildings.
Every material has an environmental footprint. Mass Plywood Panel, a new entrant in the mass timber category, has the potential to revolutionize the mass timber sector. The environmental consequences of producing Mass Ply Panels (MPP) are carried forward into the life cycle of products made from it, such as wooden structures. Life cycle inventory (LCI) data cover forest regeneration through to final product at the mill gate. There is over 20 years of life cycle assessment (LCA) research on major US produced forest products, both structural and nonstructural, from four major regions.
This report describes the cradle-to-gate (mill) energy and materials required for producing MPP produced in Oregon and the subsequent releases into the environment. The environmental impacts, global warming, ozone depletion, acidification, smog, and eutrophication are discussed.
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 building industry currently consumes over a third of energy produced and emits 39% of greenhouse gases globally produced by human activities. The manufacturing of building materials and the construction of buildings make up 11% of those emissions within the sector. Whole-building life-cycle assessment is a holistic and scientific tool to assess multiple environmental impacts with internationally accepted inventory databases. A comparison of the building life-cycle assessment results would help to select materials and designs to reduce total environmental impacts at the early planning stage for architects and developers, and to revise the building code to improve environmental performance. The Nature Conservancy convened a group of researchers and policymakers from governments and non-profit organizations with expertise across wood product life-cycle assessment, forest carbon, and forest products market analysis to address emissions and energy consumption associated with mass timber building solutions. The study disclosed a series of detailed, comparative life-cycle assessments of pairs of buildings using both mass timber and conventional materials. The methodologies used in this study are clearly laid out in this paper for transparency and accountability. A plethora of data exists on the favorable environmental performance of wood as a building material and energy source, and many opportunities appear for research to improve on current practices.
As the need to address climate change grows more urgent, policymakers, businesses, and others are seeking innovative approaches to remove carbon dioxide emissions from the atmosphere and decarbonize hard-to-abate sectors. Forests can play a role in reducing atmospheric carbon. However, there is disagreement over whether forests are most effective in reducing carbon emissions when left alone versus managed for sustainable harvesting and wood product production. Cross-laminated timber is at the forefront of the mass timber movement, which is enabling designers, engineers, and other stakeholders to build taller wood buildings. Several recent studies have shown that substituting mass timber for steel and concrete in mid-rise buildings can reduce the emissions associated with manufacturing, transporting, and installing building materials by 13%-26.5%. However, the prospect of increased utilization of wood products as a climate solution also raises questions about the impact of increased demand for wood on forest carbon stocks, on forest condition, and on the provision of the many other critical social and environmental benefits that healthy forests can provide. A holistic assessment of the total climate impact of forest product demand across product substitution, carbon storage in materials, current and future forest carbon stock, and forest area and condition is challenging, but it is important to understand the impact of increased mass timber utilization on forests and climate, and therefore also on which safeguards might be necessary to ensure positive outcomes. To thus assess the potential impacts, both positive and negative, of greater mass timber utilization on forests ecosystems and emissions associated with the built environment, The Nature Conservancy (TNC) initiated a global mass timber impact assessment (GMTIA), a five-part, highly collaborative research program focused on understanding the potential benefits and risks of increased demand for mass timber products on forests and identifying appropriate safeguards to ensure positive outcomes.
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