Sequestration of carbon in harvested wood products for the United States

The Intergovernmental Panel on Climate Change (IPCC) provides guidelines for countries to report greenhouse gas removals by sinks and emissions from sources. These guidelines allow use of several accounting approaches when reporting the contribution of harvested wood products (HWP) under the United Nations Framework Convention on Climate Change. Using extensions of methods suggested by the IPCC and a software model called WOODCARB II in Microsoft Excel®, this paper presents estimates of the U.S. HWP contribution to annual greenhouse gas removals in the agriculture, forestry, land use, and land use change sector. In 2005, the contribution to removals was 30 Tg (million metric tons) C (carbon) and 31 Tg C for the Production and Atmospheric Flow Approaches, respectively, and 44 Tg C for the Stock Change Approach. This range is 17 to 25 percent of C removals by forests, or would offset 42 percent to 61 percent of residential natural gas C emissions in 2005. The contribution has declined under the Production and Atmospheric Flow Approaches since 1990 and has increased under the Stock Change Approach. The Stock Change estimate has increased because it explicitly includes C in increasing net imports of wood and paper products. The contribution estimates were validated by adjusting the half-life of products in use in order to match independent estimates of carbon in housing in 2001 and annual wood and paper discards to solid-waste disposal sites (SWDS) during 1990 to 2001. Estimates of methane emissions from wood and paper in landfills were also checked against independent estimates of total landfill methane emissions. A Monte-Carlo simulation used to assess the effect of uncertainty in inputs suggests the 90 percent confidence interval for removal contribution estimates under the three approaches is within -23% to +19%.