The carbon stock of harvested wood products in US residential houses is substantial

Harvested wood products (HWP) provide humans with services that can substitute for emissions-intensive products, while storing carbon sequestered from the atmosphere by forests. Nearly half of HWP in the US have been used for construction purposes. Due to the long-lived nature of houses, the wood within these buildings can store carbon for many decades. This study developed a new methodology to model the decay and half-lives based on national census data. Six different models were evaluated and the inverse sigmoidal decay pattern of houses was best represented using a Gamma distribution model. It adequately modelled the decay pattern of houses from the US, Canada and Norway and enabled the quantification of structural HWP carbon stocks in residential houses. For the US, it was estimated that residential houses would take about 140 years to reach 50% removal of the housing number initially constructed and 390 years to reach 95% removal. At the end of 2009, the carbon stock of structural HWP in US residential houses was estimated to be 668 MtC and the average rate of carbon storage from 1990 to 2006 was 44.7 Mt CO2e yr-1. The utilization of HWP for long-lived uses has the potential to make a major contribution to mitigating greenhouse gas emissions through carbon storage and substitution of emissions from other products such as concrete and steel. With a same amount of HWP input, structural wood use can produce a carbon pool that is 48 times larger than pulp and paper use, or 3 times larger than furniture use. In addition, this pool takes much longer to saturate. Accurate quantification of the structural HWP pool is therefore an important topic worthy of detailed investigation.