CORVALLIS, Ore. — Substituting wood for concrete and steel in the structural systems of commercial buildings reduces fossil fuel use and cuts emissions of greenhouse gases on average 60 percent, according to a recent analysis by Oregon State University researchers.
This is significant because materials are a significant component of carbon dioxide emissions associated with construction. In the United States alone, building construction and use contribute about 40 percent of total carbon dioxide emissions, according to the U.S. Department of Energy.
Reporting in Wood Fiber and Science, a professional journal, the OSU researchers from the College of Forestry and College of Engineering found that much of the savings are achieved through the use of wood as a fuel source in manufacturing. Although most of the energy used to produce building materials — whether they are wood, concrete or steel — comes from fossil fuels, wood products tend to be less energy intensive. In addition, a portion of the energy for making structural panels, beams and other wood products comes from wood wastes, which, the authors assumed, is carbon neutral.
“The study is just the first step leading to a sustainability metric for use of wood in code-compliant commercial buildings,” said Ari Sinha, professor of renewable materials in forestry and a co-author on the paper. “Generally, we know wood is renewable, resulting in lower environmental impacts in many cases than other building materials. What was lacking was confirmation and quantification of these benefits.”
The researchers analyzed structural systems in six types of buildings and assumed each would be built in Portland. The structures included an office building, exercise facility, medical center, basketball arena, residential building and warehouse.
In each case, they took a life-cycle approach, which tracks the environmental impacts of materials through five stages in the life of a building: manufacturing of materials, building construction, building operation, demolition and recycling. The researchers assumed that the choice of structural materials would not alter building operation, so their analysis ignored that aspect of the life cycle.
In addition to the six case studies, the authors analyzed a scenario in which the structural system of one of the buildings — a one-story medical center — was completely redesigned using wood products. That approach achieved the largest greenhouse gas emissions reduction, about 166 percent, over conventional construction methods using other materials. “That’s because the analysis takes carbon sequestration into account,” said Sinha. “A growing tree removes carbon dioxide from the atmosphere, and when it is used in building products, the carbon is sequestered for the life of the building.”
The authors used software developed by the Athena Sustainable Materials Institute, a nonprofit organization, to estimate the consequences of substituting wood for concrete and steel.
Kristina Milaj, a former graduate research assistant at Oregon State now with the engineering firm CH2M, performed the study in coordination with Sinha, Thomas Miller in the OSU College of Engineering and John A. Tokarczyk of the Oregon Department of Forestry, which provided financial support for the study.