Regional comprehensive environmental impact assessment of renewable energy system in California

Fossil-fuel-based energy systems pose a significant threat to the climate and ecosystem. Renewable energy is considered key to achieving carbon neutrality and the Sustainable Development Goals. California is a forerunner in promoting renewable energy and sustainable development. However, regionalized renewable energy systems are accompanied by intensive material inputs and outputs, which undoubtedly have associated environmental impacts while mitigating climate change. It is necessary to measure the spatio-temporal distribution and the comprehensiveness of these impacts in order to plan renewable energy systems rationally. In this study, a life cycle assessment (LCA) on the renewable energy system of California between 2001 and 2019 was conducted to estimate the resulting diverse environmental impacts. The results show that solar energy and biomass and waste-to-energy are the main contributors to the comprehensive life-cycle impacts of the renewable energy system in California from 2001 to 2019, accounting for 62.7% ± 1.2% and 35.1% ± 1.2%, respectively. The most prominent source of environmental impact is AP, instead of the most attention-getting category, global warming potential (GWP). Geographically, Kern currently holds the highest generation of renewable energy (15.3 TWh in 2019) in the state. The corresponding normalized and weighted environmental impact is also most notable in Kern, reaching 1.7E-02 in 2019, twice as much as in Imperial, the second largest energy producing county. From 2001 to 2019, the per kWh weighted environmental impact of California's renewable energy system decreased, but the total effects increased sixfold with the promotion of renewable energy. Overall, renewable energy systems can reduce environmental impacts compared to conventional energy sources. It can help achieve some ambitious environmental goals. However, the results of this study remind us that in the renewable energy sector, we should not only focus on greenhouse gas emissions, but in the context of social development, this case shows that acidification potential (AP), ozone depletion potential (ODP) and photochemical oxidant formation potential (POFP) need to be managed more than GWP. Given the uneven distribution of natural resources, there is still room to improve further the environmentally friendly efficiency of California's renewable energy system, which will require technological advances and improved deployment of resource management.