Comparative life cycle assessment of battery-electric and diesel underground mining trucks

Abstract

The mining sector is currently confronted with an energy market and evolving regulatory landscape that exerts pressure on the industry to consistently enhance its strategies and decision-making in support of sustainable practices. Traditionally, the ore is transported using heavy-duty trucks powered by diesel engines which have been identified as a primary contributor to environmental degradation. An emerging and technologically advanced solution of considerable interest is the implementation of battery-electric trucks, which still generates some uncertainty about its actual impact on the environment. The primary hypothesis under investigation is that battery-electric vehicles have significantly lower environmental impacts than conventional combustion vehicles. Thorough research is needed to bridge this knowledge gap and robustly understand the environmental effects of these technologies in the mining context. This study uses Life Cycle Assessment to evaluate the potential environmental impacts of battery-electric trucks compared to diesel trucks in a theoretical underground mine. The study analyses the environmental impacts around three main stages: the raw material supply for the manufacture of the vehicles, the energy supply (electricity or diesel fuel), and other indirect impacts associated with the operation of both types of trucks. The characterization methodology used is the ReCiPe2016 Midpoint (Hierarchical) using open-access software OpenLCA v1.10.3 for the impact assessment. The functional unit selected is one ton of material transported over 1 km. Our results for the baseline Chilean scenario indicate that diesel trucks have a considerably greater environmental impact in two of the five categories studied: global warming potential and stratospheric ozone depletion. The energy supply is the ‘hotspot’ for the electric truck life cycle, while the diesel truck life cycle has the operation and the energy supply as the main environmental impact sources due to the upstream and direct emissions associated with diesel supply and combustion, respectively. However, when considering particulate matter formation and water consumption, electric trucks exhibit higher impacts due to the technologies employed for generating the electricity used to charge their batteries. Furthermore, the environmental profile of the electric truck improves considerably when renewable sources of electricity substantially substitute coal in the electricity mix, as projected in the Chilean policy context. The main novelty of this study is that it is the first initiative comparing a battery-electric truck with a diesel truck considering an approach to the underground operation reality for the mining sector.