## 5 Case Study of Life-Cycle Assessment and Forest Products  
There are many life cycle assessments that deal with forest management, forest products, or related products or processes [63, 64]. While forest management is always the focus of forest certification systems, it is usually just one of many issues addressed by life cycle assessments [65-67]. This case study is a detailed greenhouse gas (GHG) life cycle assessment (LCA) for two forest product chains: pulp and paper for the production of magazine grade paper and the production of dimensional lumber [68]. It involved North American wood and product flows. The LCA included all major direct and indirect carbon and GHG emissions involving all processes from harvesting and transportation of wood to the mill to disposal of waste and recycling [68]. Dealing with a forest's carbon cycle makes the normally complex LCA even more complex. Figure 1 illustrates a forest carbon cycle that is comprised of a biological carbon cycle (forest ecosystem) and an industrial cycle (forest manufacturing) [69]. The temporal and spatial boundaries for a problem like this are not easy to define, especially because there are multiple sources of both raw materials and energy to produce the final product, varying life spans for the products, by-products, and disposed material in the cycle [70]. It is important to understand that primary biological productivity is the product of photosynthesis in which carbon dioxide and water combine using the energy of the sun to produce the elemental carbon input to the tree. At the other end of the process respiration releases oxygen to the atmosphere. The study boundaries were defined to include the wood flow from two major wood procurement regions, transportation of the wood to the mills, all manufacturing stages of both primary products (magazines and dimensional lumber) and by-products,transportation of the products to the consumer, and the final disposition of those products. This life cycle is shown in Figure 2[68]. The complexity can be shown by just the classifications and types of GHG that were included in the system. Direct carbon dioxide emissions included emissions from forest harvesting activities, pulp and paper manufacture, lumber production, and printing. Indirect carbon dioxide emissions were from transportation (of wood to the mill, finished products to the printing houses and outlets, printed magazines to newsstands and subscribers, and recycling, recovery, and disposal). The study used a carbon soil dynamics assumption that harvesting did not change soil carbon content during the rotation of a forest stand. However, this variable can be dependent upon forest type, harvest method, and utilization rate [71]. Site preparation and planting, as opposed to natural regeneration, are also sources of GHG emissions and are part of the life cycle [68]. Harvested wood and skidding harvested wood to collection points result in GHG emissions. The final fate of the forest products (type of disposal, recovery, or recycling) is also going to have a GHG impact. Figure 1: A conceptual diagram of the forest carbon cycle, from the biological cycle to the industrial forest products cycle (GPP = gross primary production, R\({}_{\text{A}}\) = autotrophic respiration, NPP = net primary production, R\({}_{\text{H}}\) = heterotrophic respiration, R\({}_{\text{R}}\) = root respiration, D = detritus, and H = harvest removal) [68,69]. The LCA of the dimension lumber chain showed that 0.22 tons of carbon were emitted per ton of lumber produced. The relative GHG contribution of the various processes were: forest management, including harvesting, contributed less than 1%, transportation of wood to the sawmill contributed 2%, sawmill production contributed 2%, transportation and distribution of the lumber to the consumer contributed 94%, and emissions from by-products and final fate contributed 2%. Ninety-eight percent of all GHG emissions were indirect [68]. The LCA of the magazines averaged about 0.31 tons of carbon per ton of magazine produced.