Modeling the Processing and Transportation Logistics of Forest Residues Using Life Cycle Assessment

This study investigates the environmental burdens of three logistics system scenarios for residue processing and transportation under different road type distributions using life cycle assessment (LCA). The three scenarios are as follows: bin truck with stationary grinder at centralized landing (base case); bundler with electric grinder; and mobile chipper at slash piles. The total distance between the forest site and the bioenergy facility is set at 50 miles one way. The functional unit is 1 bone-dry ton (BDT) of residues transported from the forest site to the bioenergy facility. Results indicate that the mobile chipper system posts the lowest global warming impact under all types of road distributions (38.2‐41.4 kg CO₂ eq [84.2‐91.3 lb CO₂ eq]), whereas the base case shows the most rapid reduction in global warming impact as highway distance increases (43.8‐56.9 kg CO₂ eq [96.6‐125.4 lb CO₂ eq]). Potential impacts from acidification, eutrophication, and smog indicate reduction as highway distance increases. Along these LCA metrics, road conditions play an important role in determining the most efficient residue collection system. As the residue piles are located further from paved highway, the bundler and the mobile chipper systems present greater environmental advantages.

Management and Policy Implications Uncertainty in the role of bioenergy for offsetting greenhouse gas (GHG) emissions has prevented wide adoption of bioenergy in the United States. Because of variations in forest site conditions across the country, understanding the environmental impacts of the logistics of forest residue transportation is an important step in maximizing the benefits and use potential of bioenergy. Currently, few studies provide a basis for enhancing management techniques during the processing of forest residues. The actual impact of the logistic scenarios described in this study depend on forest sites, because the location of slash piles may vary based on the geographic features of forest sites and logging activities. Road distances and conditions are taken into account, so forest owners/managers and policymakers would have the option of choosing the best system scenarios based on the distribution of slash piles and the road conditions of particular forest sites. The findings of this study clearly show that the environmental impact associated with the System 1 in-woods residue handling and processing decreases when the proportion of paved highway increases. The location of residual biomass in terms of the existing road conditions would justify the need for an alternate in-woods biomass processing system, such as System 2 or 3. The findings of this study may be applied to a variety of privately or publicly owned forestlands and can apply to a wide audience, including forest managers, logging companies, researchers, and alternative energy production companies. More importantly, this research can be used as a valuable reference for policymakers to improve the requirements and guidelines for managing forest slash piles and in-forest road developments.