Climate change is thought to be caused by greenhouse gas (GHG) emissions from fossil fuels, livestock and forest fires that produce carbon dioxide (CO2) and methane. There are increasing government policies regarding GHG and climate change.
For example, the Environmental Protection Agency (EPA) has Clean Air Act regulations for methane emissions from oil and gas production. CO2 emissions and sequestration are reported in national and worldwide reports as million metric tons of carbon dioxide equivalents (mmt CO2 Eq.). The metric ton used in worldwide CO2 assessments is 2,205 pounds. In this article, I’ll use the U.S. 2,000-lb. ton in my calculations of CO2 in trees.
It is remarkable that forests in the U.S. currently absorb (sequester) about 12.4% of the total GHG emissions in the U.S. Trees actually remove CO2 from the atmosphere while forest fires emit large amounts of CO2. It is obvious that preventing large forest fires can reduce the amount of GHG emissions, but it’s not always recognized that timber harvest can also reduce GHG from the atmosphere as described in previous WLJ articles (June 17, 2022, Nov. 11, 2022, and Aug. 12, 2024).
In the August 2024 article, I used data in U.S. Forest Service reports to calculate the amount of CO2 that could be sequestered in one hypothetical Douglas fir tree, a log truck load and an acre of forest. See the references and notes at wlj.net for this information and a correction to the log weights in the Aug. 12 article.
To keep focus on the local level, here I report the amount of CO2 in actual lodgepole pine trees from a logging operation on a forest stand at 6,000 feet elevation near Bozeman, MT. I cut, measured and weighed three trees, and surveyed a one-tenth acre plot to estimate the numbers and diameters (at breast height, 4-and-a-half feet from the ground) of trees per acre.
The results in Table 1 (see the references at wlj.net) show CO2 weights of 1,299 lbs. (0.65 tons) of CO2 in a 9-inch diameter 70-foot-tall tree, 396 lbs. (0.2 tons) of CO2 in a 5.75-inch diameter 65-foot-tall tree, and 264 lbs. (0.13 tons) of CO2 in a 5.25-inch diameter 42-foot-tall tree.
There are 490 live trees/acre estimated from the survey plot with an average diameter of 7.2 inches and CO2 weight of 422,600 lbs./acre (211 tons/acre). That would be 135,040 tons per 640-acre section.
These data are comparable to the hypothetical data for 12-inch diameter Douglas fir trees in the Aug. 12 WLJ article (one tree has 0.81 tons CO2, one acre has 242 tons CO2, see the references). Growth rates and weights of forest trees will vary depending on tree species, density, location, site quality, rainfall, aspect and other factors, but the amounts I calculated for lodgepole pine trees in Montana, about 0.65 tons of CO2 in a 9-inch diameter tree and 211 tons/acre of CO2, give a general idea of the amounts of emissions that can be avoided by preventing forest fires, and the amount of CO2 that can be sequestered in wood products by harvesting timber.
The Forest Service and others recognize that the carbon in wood from harvested trees in lumber, furniture, and landfills is sequestered and not released as CO2, and regenerating trees and ground cover (grass and shrubs) absorb CO2 from the atmosphere. It is apparent that a proactive program of forest management including logging, thinning, grazing and access for rapid fire suppression response would result in less CO2 emissions, more CO2 sequestration and less destructive forest fires, including on public lands.
Reducing CO2 in the atmosphere to mitigate climate change is now a primary objective of the U.S. government. Forest management, including on public lands, should be a key component of these mitigation efforts. Forests currently absorb 12.4% of the U.S. GHG emissions; aggressive forest management can increase this substantially. The past decades of preventing timber harvest because of (often exaggerated) environmental concerns should be replaced with a new program of active forest management that reduces GHG in the atmosphere and provides natural resources and economic opportunity.
This is especially the case for the Rocky Mountain states in which forests emit more CO2 than they sequester, partly because of emissions from forest fires. My calculations suggest that preventing forest fires, harvesting timber and regenerating trees in the Rockies can reduce CO2 emissions by about 211 tons/acre.
A recent memorandum of understanding (July 2024) between the American Loggers Council (ALC) and the U.S. Forest Service provides a first step in this direction. In this memorandum, the ALC and Forest Service agree that logging is an effective tool for reducing hazardous fuels and achieving forest management goals. This collaboration between industry and government is a good start to improving forest management in the U.S. — Dr. Matt Cronin
(Matt Cronin is a biologist with Northwest Biology and Forestry Company LLC in Bozeman, MT, croninm@aol.com. He was a research professor at the University of Alaska.)
References
Memorandum of Understanding Between the American Loggers Council and the USDA, Forest Service. July 2024. FS Agreement No. 24-MU-11132544-038. OMB 0596-0217, FS-1500-15. American Loggers Council Signs Historic Memorandum of Understanding with the USDA Forest Service — American Loggers Council I The National Voice for Loggers (amloggers.com)
Mann, C.N. and H.H. Lyons. 1972. A method of estimating log weights. U.S. Forest Service Research Paper PNW-138, Portland, Oregon.
Brown, J.K., J.A. Kendall Snell, and D.L. Bunnell. 1977. Handbook for predicting slash weight of western conifers. U.S. Forest Service General Technical Report INT-37, July, 1977. Ogden, Utah.
Domke et al. 2023. Greenhouse gas emissions and removals from forest land, woodlands, urban trees, and harvested wood products in the United States, 1990-2021. Resource Bulletin WO-101. Washington, DC: U.S. Department of Agriculture, Forest Service, Washington Office. 10 p. Greenhouse Gas Emissions and Removals From Forest Land, Woodlands, Urban Trees, and Harvested Wood Products in the United States, 1990–2021 (usda.gov)
U.S. Forest Service. 2021. FS-1189c | December 2021. Forest Carbon Status and Trends. R&D Hot Topic: Forest Carbon Status and Trends (usda.gov)
Global maps of twenty-first century forest carbon fluxes | Nature Climate Change
Environment: How much carbon do forests absorb? | World Economic Forum (weforum.org)
Wood Species – Moisture Content and Weight (engineeringtoolbox.com)
Wood and Moisture | The Wood Database (wood-database.com)
Douglas Fir Pseudotsuga menzieslif(Mirb (usda.gov)
Lodgepole Pine Pinus contorta Dougl (usda.gov)
how much CO2 from wood – Search (bing.com)
Calculating the Carbon Stored in Wood Products – WoodWorks | Wood Products Council
Carbon Storage in Wood Products main.pdf (sciencedirectassets.com)
FTM: The Fire and Tree Mortality Database | US Forest Service Research and Development (usda.gov)
Dry wood is composed of cellulose, hemicellulose and lignin, which are compounds comprised of other elements besides carbon, like hydrogen and oxygen.
(Copilot with GPT-4 (bing.com), chemical formula for burning wood – Search (bing.com), wood burning chemical reaction formula – Search (bing.com)
Notes
Pg C yr−1 stands for petagrams of carbon per year. A petagram is equivalent to one billion metric tons of carbon, or 10^15 grams of carbon. It’s a unit used to quantify the exchange of carbon in the Earth’s carbon cycle.
Table 1. Lodgepole pine tree measurements*
| Age | height | DBH | Tree lbs. | Slash lbs. | Log lbs. | Water lbs. | dry wood lbs. | Carbon lbs. | CO2 lbs. | CO2 Tons | |
| Tree 1 | 128 | 70 | 9.00 | 1180 | 160 | 1020 | 472 | 708 | 354 | 1299 | 0.650 |
| Tree 2 | 100 | 66 | 5.75 | 360 | 100 | 260 | 144 | 216 | 108 | 396 | 0.198 |
| Tree 3 | 78 | 42 | 5.25 | 240 | 100 | 140 | 96 | 144 | 72 | 264 | 0.132 |
Table 2. Lodgepole pine trees on one acre (estimated from 1/10th acre survey plot)
All trees Live trees Dead trees Number 610 490 120 DBH average 6.9 7.2 5.4 Log weight 770 Water weight 300 Dry wood weight 470 Carbon weight 235 CO2 weight 862 CO2 weight for 490 trees/acre 422,600 (211 tons)
1 ton = 2,000 lbs. Logs are the trunk to a 4″ diameter top,
For the survey plot live log weights were estimated considering the average DBH 7.2″ and estimated as the average weight of the measured individual trees with DBH 9″ & 5.75″ (1180+360)/2=770 lbs.)
Water content is 40% of wood weight, dry wood weight is log weight minus water weight,
Carbon weight is 1/2 of dry wood weight, and CO2 weight is 3.67 times carbon weight.
Data from Cronin, August 12, 2024, WLJ
A hypothetical Douglas fir tree:
Correction from August 12 WLJ numbers:
• Logs 12 inches in diameter at the base, cut into four 16-foot-long logs = 64 feet = 1,280 pounds (Mann and Lyons 1972, Table 3).
Log weight was reported incorrectly in the August 12 WLJ as 960 lbs. The calculations below are corrected using log weight of 1,280 lbs.
• Slash, the tree top smaller than 4-inch diameter, branches and needles = 194 lbs. (Brown et al. 1977, Table 2).
• Logs + slash = 1,474 lbs. wood.
• 1,474 lbs. – 40% water content 590 lbs. water = 884 lbs. dry wood.
• Carbon comprises half of dry wood, 884 lbs., dry wood = 442 lbs. carbon.
• The weight of CO2produced from the carbon in wood when it’s burned or decayed is 3.67 X the weight of carbon (CO2/carbon ratio = 3.67).
• 3.67 X 442 lbs. carbon = 1,622 lbs. CO2 = 0.81 tons potential CO2 in the tree.
A log truck load:
• With 28 tons of logs = 56,000 lbs.
• 56,000 lbs. – 40% water content = 33,600 lbs. dry wood.
• With carbon comprising 1/2 of wood = 16,800 lbs.
carbon.
• 3.67 X 16,800 lbs. = 61,600 lbs. CO2 = 30.8 tons potential CO2 in a log truck load.
Per acre:
• 132,300 lbs. carbon/acre.
• 3.67 X 132,300 lbs. = 485,104 lbs. CO2 = 242 tons potential CO2 per acre.
