Forest Carbon Storage 1 a Summary of the Greenhouse Gas Implications of Forest Carbon Storage

This chapter describes the development of material-specific estimates of changes in forest carbon storage in EPA's Waste Reduction Model (WARM). It summarizes the approach used to estimate changes in forest carbon storage in managed forests resulting from source reduction and recycling of wood and paper products. Forests absorb (i.e., sequester) atmospheric carbon dioxide (CO 2) and store it in the form of cellulose and other materials. In the early stages of growth, trees store carbon rapidly; consequently, as tree growth slows, so does carbon sequestration. Trees naturally release carbon throughout their life cycle as they shed leaves, branches, nuts, fruit, and other materials, which then decay; carbon is also released when trees are cleared and processed or burned. When paper and wood products are recycled or the production of these materials is avoided through source reduction, trees that otherwise would be harvested are left standing in forests. In the short term, this reduction in harvesting results in more carbon storage than would occur in the absence of the recycling or source reduction. Over the long term, when forest managers find they have more trees standing resulting from reduced harvesting, they will respond by planting fewer trees; therefore, while the carbon storage effect of source reduction and recycling is high in the short term, it is less pronounced in the long term. WARM evaluates forest carbon storage implications for all wood and paper products, which include all of the paper types in WARM, 1 dimensional lumber, medium-density fiberboard (MDF), and hardwood flooring. Paper products are primarily nondurable goods, or goods that generally have a lifetime of less than three years (EPA, 2008, p. 76). Wood products such as dimensional lumber, MDF, and wood flooring are considered durable goods because they typically have a lifetime of much longer than three years (Skog, 2008). Because of the differences in harvesting practices, use, and service life of paper and wood products, EPA analyzes the forest carbon storage implications for paper products separately from wood products. In the United States, uptake by forests has long exceeded release, a result of forest management activities and the reforestation of previously cleared areas. EPA estimated that the 2008 annual net carbon flux (i.e., the excess of uptake minus release) in U.S. forests was about 792 million metric tons of carbon dioxide equivalent (MMTCO 2 E), which offset about 3 percent of U.S. energy-related CO 2 emissions. In addition, …