Carbon footprint of the predominant mechanized timber harvesting methods in the Northeastern US

Estimating carbon footprint of forest operations is essential to budget the environmental impacts of the industry. The study objectives were to a) assess the carbon footprint of whole-tree (WT), cut-to-length (CTL), and hybrid cut-to-length (Hyb CTL) harvesting methods in the Northeastern US; b) assess global warming potential of various processes involved in timber harvesting for different harvest methods; and c) evaluate variation in the carbon footprint for the summer and winter harvest. SimaPro 9.3.0.3 software and allied databases (USLCI and US-EI 2.2) adhering to ISO 14,040 and 14,044 standards were used for cradle-to-gate life cycle assessment (LCA) with a functional unit of 1 tonne of green roundwood. Tool for reduction and assessment of chemicals and other environmental impacts (TRACI v 2.1) was used for impact assessment. The input variables were quantity of fuel (liter tonne-1) and lubricants (kg tonne-1) for respective harvesting operations. The results of LCA showed that carbon footprint was highest for WT (11.57 kg CO2 eq), followed by Hyb CTL (11.09 kg CO2 eq) and CTL (9.91 kg CO2 eq) methods. Secondary transportation (trucking) had highest global warming potential among the processes. Winter harvest had a higher carbon footprint than summer by 2 and 3 percent, respectively, for CTL and Hyb CTL methods. The extra time needed to warm up engine resulted in a higher carbon footprint for winter harvest. Higher carbon footprint for WT method can be attributed to greater number of equipment involved for WT resulting in more fuel consumption, compared to other methods. Among the stump-to-landing processes, skidding contributed foremost in WT, whereas felling and processing in CTL, and processing in Hyb CTL, respectively. These results could be used in the upstream process for future LCA of different wood products manufactured in the region.