This page last reviewed July 2, 2013
Compliance Offset Protocol U.S. Forest Offset Projects - Instructions
Volume and Biomass Equations for Forest Offset Projects in California, Oregon, and Washington
Offset Project Operators with projects located in California, Oregon, and Washington must estimate and convert biomass to tons of CO2e on a per acre basis, within the boundary of an offset project. To accomplish this, ARB has approved the use of biomass equations generated from the United States Forest Service Forest Inventory and Analysis (FIA) National Program to estimate biomass. These equations are the same equations used to generate the Common Practice estimate for each Assessment Area. Offset Project Operators must use these same equations when modeling growth and yield for their projects. The form of the equations varies by region.
Volume and biomass estimates for projects in California, Oregon, and Washington are determined using regional equations (USFS, Region 1). These equations estimate volume and biomass in the various components of the above-ground portion of the tree, including the stump, the bole, the top branches, and leaves. The Cairns equation (Cairns, Brown, Helmer & Baumgardner, 1997) must be used to calculate CO2e in the below-ground portion of the trees.
located in states outside
of California, Oregon, and Washington but within the
contiguous United States utilize FIA regional cubic volume equations
incorporate the Forest Service’s Component Ratio Method to estimate the
in the non-bole portions of the tree. If your project is outside
of California, Oregon, and Washington, you must use the Component
Method to calculate biomass; see page entitled, “Instructions – U.S. States Except California,
Oregon, and Washington."
- Identify the Supersection your project is located in from the Supersection Maps in the table on the Compliance Offset Protocol U.S. Forest Projects webpage.
- Use the appropriate volume equation identified in the document “Volumetric Equations for California, Oregon, and Washington (May 13, 2009)1” for each tree species in your project.
- Use the appropriate biomass equation identified in the document “Biomass Equations for California, Oregon, and Washington (May 13, 2009)2.”
 Reference: Volume Estimation for the PNW-FIA Integrated Database; U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station.
 Reference: Regional Biomass Equations Used by FIA to Estimate Bole, Bark, and Branches; U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station.