Accounting for harvested wood products in a forest offset program: Lessons from California

Carbon offset programs, such as that overseen by the California Air Resources Board (CA ARB), have emerged as a strategy for climate change mitigation. Offset projects sequestering carbon earn credits that can be traded on the Cap-and-Trade market to compensate for carbon emissions. The carbon stock embodied in harvested wood products can make up a substantial portion of the sequestered carbon in forest offset projects. In this paper we investigate the sensitivity of the calculations for the number of credits allocated to a forest offset project in the California system. We also examine how alternative models for the decay of harvested wood products might better reflect the dynamics of both the lifetime and cascade chain progression of the products and how this might change the amount of credits earned. The results suggest improved data collection and refinement in methodology would help to improve accuracy and reduce uncertainty in a large and important carbon stock. We conclude with offering suggestions on how an understanding of the dependence of harvested wood product stocks on life cycle parameters might affect the economics of offset programs and assist targeted mitigation efforts.