Assessing the Climate Benefits of Hybridization in Forest Harvesters: A Life Cycle Perspective

Hybrid-electric powertrains have emerged as a promising solution for reducing fuel consumption and greenhouse gas (GHG) emissions in mechanized forest operations. This study presents a cradle-to-grave life cycle assessment (LCA) comparing a conventional diesel engine and a hybrid-electric powertrain used in forestry harvesters. The assessment was conducted in SimaPro using the IMPACT World+ midpoint method and the Average Dissipation Rate (ADR) approach for mineral resource dissipation. Two functional units were used: a primary, productivity-normalized unit of 1 m3 of harvested wood, and a secondary engine-level unit of one harvester engine system over a lifetime of 15,000 operating hours. Results showed that the operation phase dominated most environmental impact categories. On the engine-hour basis, the hybrid-electric powertrain reduced climate change impacts by 6.9% and fossil and nuclear energy use by 6.6% relative to the conventional diesel engine; when normalized per m3 of harvested wood using the average productivity of each system, these reductions increased to 26.4% and 26.4%, respectively, reflecting the hybrid system’s combined advantage in fuel efficiency and productivity. Most other operation-driven categories showed a similar pattern, including ozone layer depletion, terrestrial acidification, freshwater eutrophication, marine eutrophication, particulate matter formation, photochemical oxidant formation, and water scarcity. Land occupation, which increased by 10.0% for the hybrid system on an engine-hour basis, instead decreased by 13.2% on a per-m3 basis. However, freshwater ecotoxicity, human toxicity non-cancer, ionizing radiation, and mineral resource dissipation remained higher for the hybrid system on both bases, because of the additional electric motor, power electronics, and supercapacitor. Overall, the hybrid-electric powertrain improves the environmental performance of forestry harvesters on a like-for-like service-output basis, although increased material requirements and resource use for specific categories remain important trade-offs for future technology development.