Environmental impacts of roundwood supply chain options in Michigan: life-cycle assessment of harvest and transport stages

Here, we analyze greenhouse gas emissions and fossil energy demand for roundwood supply chain activities (harvesting and transport) within the state of Michigan. A life-cycle assessment was completed, relying on a combination of peer-reviewed literature, national databases, and primary data collected from Michigan loggers and truckers. Several equipment configurations and operating scenarios for roundwood harvesting have been considered. Results indicated that a full processor/forwarder is the best combination of harvesting equipment, with greenhouse gas emissions of 9.9-14.7 kg CO2eq/green tonne, due to relatively low inputs and high reported productivity, although environmental impacts of harvesting depend strongly on the intensity of harvest being conducted. Bimodal truck + rail transport has environmental burdens roughly one third to half that of typical log truck transport at longer transport distances, directly related to the increased fuel efficiency of rail transport. Aggregated results for roundwood supply within Michigan are comparable to similar studies in other regions, although the mechanization of the harvesting industry and large size of Michigan log trucks are factors in the smaller environmental burden. A sensitivity analysis indicated that a variety of factors related to truck transport (distance, fuel economy, load factor, truck capacity) are the most influential for overall environmental impacts of the forest biomass supply chain. Environmental impacts associated with roundwood supply are quite low in comparison to the carbon content and embodied energy of delivered wood, implying that roundwood supply activities do not preclude beneficial use of this feedstock in biofuels or bioenergy applications. (C) 2014 Elsevier Ltd. All rights reserved.