Biomass Equations

The biomass equations have been obtained from the United States Forest Service Forest Inventory and Analysis (FIA) National Program. The equations are the same equations used to generate the Common Practice estimate for each Assessment Area (by site class where applicable). Project Developers must use these same equations for their projects.

The form of the equations varies by region. The equations for Alaska, California, Hawaii, Oregon, and Washington incorporate regional equations to estimate biomass in the various portions of the above-ground portion of the tree, including the stump, the bole, the top branches and leaves.

The equations for the remainder of the United States utilize FIA regional cubic volume equations and incorporate the Forest Service’s Component Ratio Method to estimate the volume in the non-bole portions of the tree. Implementing the Component Ratio Method consists of first calculating gross cubic foot volume of each tree, living and dead. Gross cubic foot volume must then be converted to sound cubic foot volume by subtracting rotten and missing cull volume. Biomass is then calculated for individual tree components for each tree using the Component Ratio Method, with DBH and sound cubic foot volume as inputs.

Projects in Alaska, California, Hawaii, Oregon, and Washington

Steps: References
  1. Identify the Supersection your project is located in from the GIS Supersection Shape File.
  2. Use the appropriate volume equation identified in the column to the right for California, Oregon, or Washington
  3. Use the appropriate biomass equation identified in the column to the right for Alaska, California, Hawaii, Oregon, or Washington
Batch 2.0 (projects listed June 28, 2017 or later)

Batch 1.1 (projects listed March 25, 2011 or later)

Batch 1.0 (optional for projects listed prior to March 25, 2011)

Projects in the Continuous Continental 45 States
(the United States, excluding AK, CA, HI, OR, WA)

Steps: References:
  1. Identify the Supersection your project is located in from the GIS Supersection Shape File.
  2. Identify the volume equation to use for each species in your project by Supersection in the attachment identified as: Volume Equation References and Coefficients by Species for Supersections outside of California, Oregon, Washington, Alaska, and Hawaii. The coefficients for the equations are provided in the same document.
  3. Calculate gross cubic foot volume for each tree, using the equations provided, from a 1 foot stump to a 4 inch top. This will yield the value for VOLCFGRS which must then be converted to VOLCFSND (sound cubic foot volume) by subtracting rotten and missing cull volume in the central stem of each tree.
  4. Download “Biomass Estimation using the Component Ratio Method” and follow the instructions to calculate biomass for each tree using VOLCFSND from Step 3 and DBH.

Additional References