Authors:
- Ashley Prentice, Forest Carbon Specialist, Colorado State Forest Service
- Ethan Bucholz, Ph.D., Forest Monitoring Program Manager, Colorado State Forest Service
- Tony Vorster, Ph.D., Research Scientist, Natural Resource Ecology Laboratory, Colorado State University
Forest Carbon Beyond the Woods
Forest management in Colorado will continue to play a vital role in supporting watershed health, reducing wildfire risk, maintaining ecosystem resilience and supplying wood products. Forest management often involves the removal of woody biomass ranging from small diameter trees and ladder fuels to merchantable timber as part of the process. Once biomass is removed from the forest, it follows several pathways, each affecting how long the carbon contained in that wood is retained before eventual release to the atmosphere.
Woody material left on site is either scattered as slash, chipped, or piled and burned, releasing the carbon immediately or over time as it decomposes or combusts. The wood removed from the forest is utilized for short-lived products like firewood, fencing, or pallets, or may become long-lived products such as dimensional lumber, engineered timber or bio-oil. Some byproducts of harvesting, such as bark, sawdust and mill residues, can be used for bioenergy or mulch, or discarded and decomposed in solid waste disposal sites (i.e., landfills).
Carbon can remain stored in harvested wood for extended periods- especially in long-lived products (e.g., dimensional lumber), where storage can last for decades to centuries. Short-lived products (e.g., firewood), on the other hand, release carbon within a few years. Additionally, products can be recycled for new uses or enter landfills where they decompose slowly, leading to extended carbon storage in solid waste disposal sites. Wood products can even provide an indirect carbon benefit by replacing fossil fuel derived materials, such as steel, concrete and natural gas.
This diversity of outcomes makes carbon accounting for harvested wood products (HWP) both important and challenging — important because each pathway stores or releases carbon differently and challenging because tracking these various uses and fates requires detailed data and tracking methods. Further, given that Colorado imports roughly 90% of the consumer-purchased wood products (Barel et al., 2025), coupled with an estimated 2.4 million acres of Colorado forest at the highest priority level for treatment (2020 Colorado Forest Action Plan), opportunities exist for sourcing more wood products from Colorado forests.
We recently completed an accounting of carbon stored in Colorado’s harvested wood products. This S&D Byte provides key findings, trends over time and context from this inventory. The inventory reflects timber harvest data spanning 65 years (1954 to 2019) and will be updated periodically. To read the full report, please visit the CSFS Forest Carbon webpage. Another S&D Byte will focus on the forest ecosystem carbon accounting from this full report.
Piecing Together the Past: 65 Years of Harvest Records
To build this inventory, we compiled data on 65 years of harvest quantities across different ownerships. We drew upon several data sources to reconstruct the history of harvest in the state. The earliest data came from the Western Wood Products Association (WWPA) statistical yearbooks, based on annual mill surveys starting in 1954. After WWPA discontinued reporting in 2000, we filled gaps using USDA Four Corners Reports, USFS Cut and Sold Reports and Bureau of Land Management records.
Ownership was grouped into four categories: National Forest System (NFS), other federal lands, state and local government and private or Native American lands. These datasets varied in coverage and consistency, requiring careful integration (see Appendix B of the full report). The result of this data gathering and integration is the most comprehensive picture to date of harvest activity over time in Colorado, and the basis for the HWP carbon estimates presented in this report.
From 1954 to 2019, Colorado saw a total of 9,900 million board feet (MMBF) harvested. We found a dramatic shift in Colorado’s timber industry after 1979, with harvest volume dropping by nearly 50% (Figure 1). From 1954 to 1979, annual harvests averaged 218 MMBF per year, but this declined to just 105 MMBF per year from 1980 to 2019. NFS lands dominated timber production during the earlier period, accounting for 97% of harvests through 1977, but by the late 1990s, non-NFS lands took on a greater share, peaking at 74% in 1999 (Figure 1).
The overall decline coincided with significant economic and market changes in the late 1970s and early 1980s, including log supply shortages and the closure of large sawmills in Durango, Pagosa Springs and Walden. By the late 1990s, timber output on non-NFS lands increased as mills struggled to stay operational amid economic challenges, wildfires, and insect outbreaks. Overall, NFS lands contributed 76% of total harvest volumes over the study period, with private and Native American lands making up 22% and state and local lands contributing about 1%.
Tracking Carbon: HWP Stocks and Fluxes Over Time
We tracked carbon in HWP over time using a model developed by the US Forest Service (Stockmann et al., 2014) and adapted by Groom Analytics LLC, CAL FIRE and the Oregon Department of Forestry. The model tracks the fate of harvested timber through various stages, starting with timber product allocation (e.g., sawlogs, pulpwood) and then assigning those products to primary product categories (e.g., lumber, panels). These allocations are used to estimate carbon stored in wood products actively in use or how much is discarded over time. Factors such as product half-lives, which estimate how long products remain in use, and discarded product disposition ratios, which estimate the proportion of products sent to landfills versus those burned or recycled, are applied to model the fate of harvested carbon. This modeling approach enables the tracking of carbon stocks and changes across multiple decades but does not account for greenhouse gas emissions during timber harvest, log transportation, manufacturing, nor substitution effects of wood products or bioenergy. We accounted for wood products produced from Colorado’s forests, not wood imported to the state.
As of 2020, 5.8 TgC were stored in harvested wood products, with an uncertainty analysis estimating a 90% confidence range of 4.7 to 6.8 TgC. This carbon storage is split nearly in half between products in use (54%; 3.2 TgC) and solid waste disposal sites (46%; 2.7 TgC). Carbon stocks grew more rapidly through the 1970s due to higher harvest rates and more gradually after, driven by retired products accumulating in solid waste disposal sites and fewer new products entering the system. Products with short life spans, such as crates or pallets, entered the waste stream quickly, while longer-lived uses like housing framing continued to store carbon as products-in-use for decades.
Annual changes in HWP carbon storage show that the state’s HWP has consistently acted as a carbon sink for more than six decades, driven by carbon added annually and stored in solid waste disposal sites (Figure 2). Carbon storage increased most rapidly from 1955 to the late 1970s, fueled by steady growth in products in use. Carbon in solid waste disposal sites grew steadily each year, helping maintain this carbon sink, even as products in use stocks declined in some years (like years in the 1980s and 2000s), when fewer products entered the PIU pool. The annual net change in carbon storage peaked at 0.227 TgC in 1969 but fell to a low of 0.011 TgC in 2004 (green line in Figure 2).
HWP’s Role in the Bigger Carbon Picture
We also calculated the HWP carbon flux for the same time period used for the forest ecosystem flux estimates (2002 to 2019) to allow for integration and comparison of the two carbon fluxes. HWP acted as a consistent carbon sink during this time, adding a net average of 0.034 TgC per year. The HWP carbon stock is small compared to carbon stored in the forest ecosystem (only 0.4% of total forest carbon) and the change/flux from HWP is also relatively small (4% of the magnitude of the forest ecosystem flux). The HWP carbon sink is similar in size to Colorado’s annual average methane and nitrous oxide wildfire emissions.
These findings highlight the supporting role of the wood products industry in utilizing harvested wood and continuing to store carbon from forest management. While HWP alone won’t drive the state’s forest carbon trajectory, its contribution is important when integrated with broader goals of forest resilience and wildfire risk reduction.
Maximizing the use of harvested woody material, particularly in longer–lived products, extends carbon storage in HWP, supports the state economy and helps offset rising forest management costs. Traditional wood markets (e.g. dimensional lumber) have declined in Colorado for some time. In 2020, there were 46 primary wood processing facilities in the state, down 42 from 2002 accounts (Irey, 2023). As estimated in 2020, 55% of Colorado lumber mills are small, producing less than 2 million board feet (166,666 cubic feet) annually, however the remaining 45% each produce greater than 11 million board feet (916,666 cubic feet) annually, for an average mill production of 5.3 million board feet (416,666 cubic feet) (Irey, 2023). Recently, more emphasis has been placed on alternative biomass industries, like mass timber and biochar, that could potentially see additional longer–lived products make their way to market with Colorado wood. However, alternative biomass industries are relatively new, meaning our methods of tracking their contributions to overall Colorado sink/source dynamics will need to be developed in concert with their introduction/expansion.
Conclusion
Harvested wood products have played a consistent, though minor, role in Colorado’s forest carbon story, storing carbon for varying lengths of time depending on how biomass is used after harvest. This novel effort to compile 65 years of harvest records provides the most comprehensive HWP carbon inventory to date for the state. Although carbon stocks in HWP are small compared to the forest ecosystem overall, they continue to represent a measurable and persistent carbon sink. Understanding and tracking these trends is essential as Colorado explores new and existing markets for forest products and seeks to maximize the value of removed biomass.
Relevant resources
The model input data, including annual Colorado harvest volumes, conversion factors, and timber product ratios are available in the Downloads section of the CSFS Forest Carbon webpage. The full spreadsheet of results, including carbon storage, emissions and cumulative changes in timber product pools and emissions across ownerships is also available in the Downloads section. The full report is also available for download under the Downloads section of the website link.
For more information, visit the CSFS Forest Carbon webpage to download the full report, model input data and complete model results.
Key definitions
Mill survey: A collection of data that tracks the volume, sources, and types of wood processed by sawmills and other primary wood processing facilities.
Products in use (PIU): Harvested wood products that remain actively in service, such as lumber used in construction, furniture, or other long-lived wood materials, continue to store carbon until they are discarded or repurposed.
Solid waste disposal site (SWDS): Facilities where discarded wood products, such as construction debris, retired furniture, railroad ties, pallets or fencing materials are deposited. These include landfills and dumps, where carbon from wood products is released through decomposition.
References
Baral, Srijana; Mackes, Kurt; West Fordham, Amanda; Anderson, Nathaniel; Gaetani, Maria. 2025. Woody biomass utilization, consumption and production in Colorado. Gen. Tech. Rep. RMRS-GTR-445. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 40 p. https://doi.org/10.2737/RMRS-GTR-445
Colorado State Forest Service. (2020). Colorado Forest Action Plan. https://csfs.colostate.edu/media/sites/22/2020/10/2020-ForestActionPlan.pdf
Irey, B. (2023). Colorado’s Forest Products Industry and Timber Harvest, 2020 [Unpublished data]. University of Montana, Bureau of Business and Economic Research.
Stockmann, K., Anderson, N., Young, J., Skog, K., Healey, S., Loeffler, D., Butler, E., Jones, J. G., & Morrison, J. (2014). Estimates of carbon stored in harvested wood products from United States Forest Service Rocky Mountain Region, 1906-2012.
Collaborators
CSFS and the Colorado State University Natural Resources in Ecology Laboratory are grateful for the support and collaboration from the United States Forest Service (USFS) Pacific Northwest and Rocky Mountain Research Stations, the USFS FIA program, CalFire and Groom Analytics, LLC.