Real-time Estimates of Logging Equipment Carbon Emissions in the Southeastern United States

Abstract

Whole tree harvesting using mechanized equipment is widely practiced in Southeastern U.S. forestry, yet limited field data exist on exhaust emissions under real-world conditions. This study addressed this gap by measuring carbon dioxide (CO₂) and carbon monoxide (CO) emissions from active logging machinery using Portable Emissions Measurement Systems (PEMS). Emissions were evaluated across factors including Diesel Exhaust Fluid (DEF) usage, machine type, engine power group, activity type, grapple size, and transmission type. DEF-equipped machines emitted 16.93 g/kWh less CO₂ (p < 0.001) and 0.108 g/kWh less CO (p < 0.001) on average than non-DEF machines. Among equipment types, feller bunchers recorded the highest CO₂ emissions (345.18 g/kWh), followed by skidders (304.63 g/kWh), with loaders emitting the least (221.50 g/kWh). Regression analysis confirmed that loaders emitted 116.98 g/kWh less CO₂ (p < 0.001) than feller bunchers, while skidders emitted 56.20 g/kWh less (p < 0.001). Loaders also maintained the lowest average CO emissions (0.115 g/kWh), compared to 0.008 g/kWh and 0.002 g/kWh for feller bunchers and skidders, respectively. CO₂ emissions were highest during loaded skidding and lowest during idle. Mid-powered machines (165–184 kW) exhibited the highest CO₂ output, while higher-powered units (185–203 kW) were more carbon efficient (p < 0.001). Transmission type also influenced emissions skidders equipped with hydrostatic drives emitted less CO₂ than those using continuously variable transmissions (p < 0.01). These results demonstrate the effectiveness of Tier 4 standards in reducing emissions and underscore the influence of equipment characteristics and operational factors on carbon outputs during logging.