By Robert Perschel, Executive Director, New England Forestry Foundation, and R. Alec Giffen, Senior Science and Policy Fellow, Clean Air Task Force. Photo by John Horner, courtesy of Rhode Island School of Design.
A new report from an international team of scientists concludes that managing forests better and using engineered wood products to build tall buildings in urban areas could have a major effect in addressing damaging climate change. (Buildings as a global carbon sink, Churkina, et al).
In this two-part blog, we will first take an in-depth look at Churkina et al.’s findings from a climate mitigation standpoint, and in Part 2, we will look into the in-forest consequences of actively managing New England’s forests for increased wood construction.
In the Nature Sustainability paper, experts from Yale University, Potsdam Institute for Climate Impact Research and Tsinghau University analyzed how much new construction will be needed to accommodate the expected increase in urban dwellers over the next 20 years—another 2.3 billion city dwellers worldwide. They calculated that just creating that many buildings using concrete and steel would use up 60 percent of the remaining carbon budget available if the world wants to keep temperatures from exceeding 2 degrees Celsius. That doesn’t allow enough room in the carbon budget for transport, heating and cooling buildings, and raising food. Put another way, if we continue to build with steel and concrete, and if we fail to significantly reduce the greenhouse gas emissions associated with the production of steel and concrete, the authors contend we will cook the planet. However, the authors suggest an alternative future, that wood from sustainably managed forests, manufactured into engineered wood building components that can substitute for steel and concrete, can reduce the problem.
They state:
“In a few decades, a material revolution, scaled in it its application to global urbanization and to the sustainable capacities of its forest sources, may balance material supply, material demand and environmental burdens and benefits while answering the challenge of urgent climate action.”
The report identified three areas of potential carbon savings and offered carbon reduction estimates for two of them. The first involves reducing the manufacture and use of steel and concrete, avoiding carbon pollution from the manufacturing process. Although wood production also uses fossil fuels to transport timber and saw it into lumber, the authors calculate that the amount of pollution is far smaller than that required for steel and concrete manufacture, both of which require heating to above 2,500 degrees Fahrenheit. The authors estimate that as much as 36 gigatons of carbon dioxide emissions might be avoided if we made a strong transition to wood buildings, equivalent to reducing current emissions by nearly 4 percent.
A second form of climate mitigation occurs when trees remove carbon from the atmosphere and that carbon is captured in the engineered wood products within the buildings for long periods of time. As more buildings are constructed out of wood, more carbon is stored. The authors calculate that there is the potential to store 9 percent of the total existing carbon in our forests by expanding the urban carbon storage pool over the next thirty years. The authors calculate that this could result in storing as much as 73 gigatons of carbon dioxide in new buildings—carbon dioxide locked safely away. With mortality of mature trees increasing due to climate stress, finding a way to protect the carbon already captured by trees becomes increasingly important. These long-term carbon storage benefits contrast with a negative climate impact if whole trees that would otherwise live for a long time are harvested specifically to burn them to generate electricity; harvesting should be driven by long term products.
The third area of potential carbon savings is tied to increasing the pool of carbon now stored within the forests of the world, which requires protecting forests from conversion to fields, solar farms, and buildings and changing our management to increase storage of in-forest carbon. The authors did not analyze this effect, but noted that forest management could produce a positive climate effect in the forest even while increasing the production of timber for construction. They warn that a precondition for achieving higher harvest levels and maintaining carbon storage in forest is preserving forest sustainability and continuing re-forestation efforts as well as leaving biologically valuable or vulnerable forests in reserve. They authors offered no predictions for carbon savings or losses for this category.
Works like that of Churkina and her coauthors are notoriously complex and dependent on a wide variety of assumptions, but the new study squares with a number of other studies on related topics. For example, Oliver, et al (2014, Carbon, Fossil Fuel, and Biodiversity Mitigation With Wood and Forests) calculated that global emissions could be reduced by 14-31 percent by using wood already growing but un-utilized. Matthews, et al. (2014, Carbon impacts of using biomass in bioenergy and other sectors: forests) compared using wood from sustained yield forestry to substitute for other materials and found that it can reduce greenhouse gas emissions significantly and outperforms just allowing the forests to continue growing. NEFF’s own studies conclude that substituting wooden construction throughout New England for steel and concrete in low-rise buildings could reduce greenhouse gas emissions by an amount equal to removing 750,000 cars from the road (Gosline 2014, The Greenhouse Gas Benefits of Substituting Wood for Other Construction Materials in New England). Blane Grann concluded that construction with cross-laminated timber is climate beneficial (Grann 2013). The International Panel on Climate change put it this way:
“Sustainable forest management aimed at providing timber, fibre, biomass, non-timber resources and other ecosystem functions and services, can lower GHG emissions and can contribute to adaptation.” (Arneth et al 2019).
Even the most pessimistic assessment we have seen (Stubert, et al. 2019) reaches the conclusion that substituting wood for steel and concrete could have benefits depending on conditions. While Stubert et al found no climate benefits in regions where 90 percent of the harvests are clearcuts and involve harvesting old growth forests, those are not the circumstances in New England.
So as we’ve discussed here, new research from Churkina et al. provides further evidence of the significant climate benefits that could result from an increased use of wood for building construction. In Part 2 of this blog, we will look at the benefits of sustainably managing forests, in New England in this case, to produce that wood.
Photo caption: Rhode Island School of Design’s North Hall, the first cross-laminated timber-steel hybrid residence hall in New England.