Carbon Accounting for Forest Products: Carbon Debt and the Time Dimension

https://doi.org/10.1007/s44391-024-00007-3

Forest Science February 2025

Author
Craig Loehle, PhD, Principal Scientist at NCASI

Abstract
To assess the carbon benefits of wood product use, this study utilized a typical stand growth model, time-in-use estimates for wood products, known decay rates of wood products in landfills, and literature values for substitution effects and a 100-year simulation using typical values. For a fast-growing forest, parity for structural lumber was achieved at about 22 years and for paper and biofuel at around 40 years. After parity, more carbon is sequestered or substituted by using wood rather than via land sparing. For a slow-growing forest, curve shapes and relationships remained the same, but stretched out to longer times. Assuming a higher fossil fuel substitution value (0.8 vs. 0.5) led to earlier parity. The proper starting point for considering benefits is not year zero (the present, looking forward) but at least many decades in the past because the use of wood products and the consequent storage of carbon in landfills has a long history. From this perspective, structural lumber has achieved parity with set-asides under all growth conditions many decades ago and is now an asset. Paper and biofuel have passed or almost passed parity for fast-growing forests. Set asides also take time to reach full biomass levels.

Keywords: Climate change; Carbon sequestration; Fossil fuel substitution; Wood products