Accounting for Carbon: The Potential of New and Innovative Technology to Store Forest Carbon and Allow for New Growth

As Massachusetts faces increasing pressure from population expansion, along with increasing challenges due to climate change, we seek a solution to the growing demand in housing that supports the local timber industry and rural economies and also creates an opportunity to store more carbon both in our buildings and across our regional forested landscape. Recent advances in timber technology have produced promising new methods for meeting some of the demand for building materials, as well as the need to store carbon. One of the most promising new technologies for small to mid-sized buildings is crosslaminated timber (CLT). CLT is a massive timber panel used in floor, wall and roof applications. Its physical structure is that of a multi-layer composite (3 to 9 layers) comprised of dimensional lumber arranged cross-wise to the next layer for bi-directional strength and stability. Pairing new CLT technologies with management practices that prioritize carbon storage and long-term resilience of forest ecosystems have the potential to both be a local source of building material and increase carbon storage from harvested timber as compared with more traditional harvesting. Simultaneously, the Northeastern United States is one of regions with the highest number of exotic forest pests. One of the pests currently impacting tree species in Massachusetts is the hemlock woolly adelgid (HWA; Adelges tsugae), a sap-sucking aphid-like insect that weakens and then eventually causes mortality in eastern hemlock (Tsuga canadensis). As these trees die,they slow their sequestering of carbon and thier ability to store more carbon is truncated. However, recent research at the University of Massachusetts-Amherst has indicated that eastern hemlock and eastern white pine (Pinus strobus) are suitable timber species as feedstock for three-layer CLT, a product typically suited to light-frame and multi-family residential construction, which could be used to meet some of the demand for housing in the region. With this potential new market for eastern hemlock as an alternative building material, it is imperative we understand the carbon dynamics at play as we think about the benefits and drawbacks of CLT and its impacts on the landscape and climate. We will investigate the carbon impacts, in terms of both storage and emissions, of harvesting eastern hemlock for use as CLT to meet some of our upcoming housing demand. We will update current methods of carbon accounting for harvested timber, as well as model scenarios of harvesting in response to HWA with and without a CLT market and assess the impacts on forest carbon and resilience. We hope that some of these findings and/or methods will be applicable across a wider array of species affected by forest pests, as we expect increasing numbers of these pests due to climate change.