Emissions life cycle assessment of charging infrastructures for electric buses

This paper evaluates and calculates the magnitude of greenhouse gases produced from the implementation of electric bus charging stations into existing bus depots concurrent with the transitioning of the commuter bus fleets into electrified powertrains. To achieve this, a comprehensive and in-depth emissions life cycle assessment is conducted and utilises the Australian based fleets as a case study, focusing particularly on Sydney city and Inner West regions. To define the scope and system boundary for this type of study, the authors have chosen bus routes that take into account city, suburban, and highway driving. The study conducts a life cycle assessment of electric bus charging stations that incorporates the greenhouse gas emissions produced from the production, transportation, installation, operations, and decommissioning phases. Additionally, three alternate scenarios are explored: time variance, high shares of renewables, and net-zero emissions by 2050. Results show that contributions from infrastructure development and the transition to electrified buses are substantially outweighed by operation emissions. The operations phase is heavily dependent on the electricity grid-mixes carbon intensity and contributes the most greenhouse gas emissions (98.8%), followed by production (0.69%), recycling and disposal (0.48%), installation (0.01%), and transportation (0.01%). The current Australian electricity grid-mix produces approximately 1.2 similar to 1.4 times more greenhouse emissions than when combusting diesel fuel. Thus, net-zero emissions will not be achieved without substantial grid-mix decarbonisation. This study also finds that regional-specific parameters heavily influences the final life cycle emissions calculations. For the case-specific scenario, it is found that transitioning the existing transport bus fleet into electric powertrains has the potential to significantly reduce the impact on climate change compared to diesel buses. However, it can only be made possible if the electricity used to charge the electric buses is generated from low carbon-intensive sources, such as renewable energy.