Life cycle based environmental impacts of future New Zealand electricity supply : a thesis presented in partial fulfilment of the requirements for the degree of Master of Environmental Management at Massey University, Manawatū, New Zealand

Thumbnail Image
Open Access Location
Journal Title
Journal ISSN
Volume Title
Massey University
The Author
Electricity use is an important contributor to the environmental impacts of many products and services in New Zealand. In this research, the life cycle based potential environmental impacts and benefits of future New Zealand low voltage electricity were assessed based on a range of electricity scenarios (for years 2018-2050). A Life Cycle Assessment (LCA) approach was adopted and Impact Assessment undertaken using twelve environmental indicators. The functional unit was the annual supply of low voltage electricity to New Zealand consumers. It was found that increasing the proportion of renewable generation in the electricity mix has clear environmental benefits. The greatest benefits are observed in indicators where current impacts are predominantly due to combustion of fossil fuels, in particular the climate change indicators, ADP fossil and PED non-renewable. A case study of a New Zealand detached house demonstrated that the choice of future electricity scenario can have a significant impact on the magnitude of the life cycle impacts of this particular long-lived product with the carbon footprint varying by up to 24% depending on the electricity scenario used. Embodied carbon accounted for 5-12% of the total carbon footprint of New Zealand electricity. The contribution of embodied carbon to the carbon footprint increases over time as more renewable generation infrastructure is constructed. Current methods for calculating the carbon footprint of New Zealand electricity for greenhouse gas reporting purposes exclude embodied carbon and utilise different allocation methods than the one used in this study for cogeneration emissions. This results in a carbon footprint that is 37-39% lower than the life cycle-based results calculated in this study. The carbon footprint of future New Zealand electricity was examined in the context of planetary boundaries. It was found that future scenarios of electricity generation and supply are not compatible with limiting climate change to a 1.5°C increase by 2050 if the electricity sector is considered in isolation. Attributing some of the benefits from electrification of the manufacturing and land transport sectors to the electricity sector can result in a carbon footprint compatible with meeting a 1.5°C climate target based on combined economic and grandfathering sharing principles. Climate targets based on other combinations of sharing principles exceeded a 1.5°C climate target by the early 2020s when 50% of the benefits of electrification of the manufacturing and land transport sectors were attributed to the electricity sector. However, if 100% of the benefits are allocated to the electricity sector, these PBs are exceeded for a period of time (2023-2047) then, the cumulative carbon footprint falls to a level below the PBs from 2048 onwards. Impacts of new electricity generation infrastructure were fully allocated to the year of construction in this research. This is an appropriate approach in the context of an absolute sustainability assessment such as a comparison with a climate change target where the timing of impacts is relevant. However, it may not be appropriate when undertaking a relative assessment comparing two products or services or when assessing short-lived products due to the potential for the results to be influenced by the timing of impacts associated with the construction of generation infrastructure.
Figure 4.1 is re-used with permission.