Life cycle assessment of electric vehicles and internal combustion engine vehicles: Future prospects

Abstract

The transportation sector is a major contributor to global greenhouse gas emissions, accounting for around 20% of primary energy consumption and 23% of CO2 emissions, with road transport playing a critical role in air pollution, particularly in the European Union. As the world increasingly turns its attention to climate change, electric vehicles (EVs) are emerging as a potentially cleaner alternative to internal combustion engine vehicles (ICEVs). However, despite the growing popularity of EVs, emissions from the transport sector have remained largely unchanged since 2005. In Türkiye, the adoption of EVs has experienced a surge, with the number of electric vehicles increasing from zero in 2012 to 81,900 in 2023. However, the environmental benefits of EVs heavily depend on the electricity used to charge them. As Türkiye continues to integrate renewable energy sources into its grid, the environmental footprint of EVs is expected to decrease. This shift, however, must be carefully tracked to guide future policies and decisions. This thesis addresses the gap in evaluating the long-term environmental impacts of EVs compared to ICEVs, specifically focusing on Türkiye's changing electricity generation mix from 2020 to 2050. The study will conduct a detailed Life Cycle Assessment (LCA) of both EVs and ICEVs, assessing key environmental factors such as global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), ozone layer depletion potential (OLDP), photochemical smog potential (PSP) and human toxicity potential (HTP). The research aims to provide insights into the future sustainability of EV adoption in Türkiye and offer valuable data for policymakers, researchers, and industry stakeholders. The LCA will be performed using the CCaLC tool, which allows for a comprehensive analysis of each vehicle's environmental impact throughout its life cycle. Türkiye's electricity generation mix has evolved significantly since 1990. In the 2000s, natural gas became the dominant energy source, while coal and hydropower continued to play substantial roles. However, renewable energy sources, including wind, solar, and geothermal, have rapidly expanded due to favorable policies and falling technology costs. This shift to renewables is essential for reducing the environmental impact of EVs, as a cleaner electricity grid will enhance the benefits of EV adoption. Although EVs have zero tailpipe emissions and offer high energy efficiency, challenges such as indirect emissions during production and emissions from electricity used to affect air quality and human health. Despite these challenges, EVs offer significant promise for reducing greenhouse gas emissions, particularly when powered by renewable or low-carbon electricity. LCA is a valuable tool for understanding the full environmental impact of products by examining all stages, from raw material extraction to disposal. LCA has been instrumental in reshaping public perception of various products, such as biofuels, which were initially considered green but later found to have significant environmental drawbacks. The LCA methodology follows four key stages: goal and scope definition, inventory analysis, impact assessment, and interpretation. For this study, the goal is to assess the environmental impact of EVs and ICEVs in Türkiye, considering the full life cycle, including raw material extraction, production, use, and disposal. System boundaries are defined using the cradle-to-grave approach, ensuring that all relevant processes are included, while negligible ones are excluded. The initial findings indicate that the production phase of EVs generates a higher environmental impact compared to other stages of the life cycle, particularly due to the energy-intensive nature of battery manufacturing. However, in the use phase, EVs are expected to outperform ICEVs as Türkiye's electricity grid becomes cleaner. For both vehicle types, the largest environmental impact stems from raw material supply, particularly the production of tires and fuel. The usage phase, driven by energy consumption, is also a significant contributor. International studies, have shown that the life cycle impacts of EVs improve over time as renewable energy sources increase, especially in countries with cleaner grids. This study developed a life cycle inventory based on a "cradle-to-grave" approach, encompassing raw material production, vehicle manufacturing and assembly, transportation, usage, and disposal phases. The functional unit is expressed in terms of the distance traveled per kilometer over the vehicle's lifespan. Assumptions for the LCA model include a sedan vehicle type, with a 20-year lifespan and 400,000 km for ICEVs, and a 15-year lifespan and 300,000 km for EVs. Both vehicle types are assumed to be driven 20,000 km annually. ICEVs consume 5.6 liters of fuel per 100 km, while EVs use 10 kWh per 100 km, and a 7% recycling rate is assumed based on Türkiye's average. The study utilizes the CML 2001 methodology to assess environmental impacts, focusing on six categories. The analysis across six impact categories reveals notable differences between EVs and ICEVs. In 2020, EVs emitted approximately 40,000 kg CO₂ eq, compared to 90,000 kg CO₂ eq for ICEVs, showing a substantial reduction in carbon emissions for EVs. Over time, both vehicle types see a reduction in GWP, with EVs benefiting more as renewable energy integration grows. Regarding AP, EVs showed a slightly higher value than ICEVs in 2020 but are expected to improve by 2050 as cleaner production methods and renewable energy use increase. For EP, EVs have a significant advantage, with values ranging from 70 to 90 kg PO₄ eq, while ICEVs maintained a steady 25 kg PO₄ eq, indicating EVs' superior potential in reducing nutrient pollution. Although the OLDP was similar for both vehicle types, EVs showed a slight edge, with a marginal decline in ozone-depleting substances during their use phase. For PSP, EVs exhibited a notable reduction, particularly during the use phase, while ICEVs contributed more to smog due to raw material extraction. Finally, while EVs demonstrated a gradual reduction in human toxicity potential, they still had a higher toxicity potential compared to ICEVs, mainly due to the environmental impact of battery production and the need for improved battery recycling. Expert opinion was gathered through a survey of 54 participants, who were asked to assign weights to six environmental impact categories. The results were used to create a unified score for each vehicle type, offering a balanced evaluation of their environmental effects. The survey revealed that 28% of participants did not own a vehicle, while 72% were vehicle owners, with 64% owning ICEVs, 6% owning HEVs, and 2% owning EVs. GWP received the highest priority, with 67% of respondents, while AP, EP, and OLDP received fewer votes across various weight categories. The assigned weights were as follows: GWP (0.25), AP (0.16), EP (0.09), OLDP (0.17), PSP (0.16), and HTP (0.17), reflecting the varying importance given to each impact category. In 2020, the overall normalized impact of ICEVs was 20% higher than that of EVs, and this difference increased to 28% by 2050 according to the survey results. This suggests that when impacts are weighted based on survey responses, EVs become a more environmentally friendly alternative over time. When equal impact weights were applied, the difference in overall normalized impact between EVs and ICEVs was 8.7% in 2020, increasing to 17.7% by 2050. However, in this case, the overall difference was less pronounced, underscoring the importance of considering weighted environmental impacts for a more accurate sustainability assessment of both vehicle types. The study also included a sensitivity analysis, examining the effects of longer vehicle lifetimes and tire usage on the environmental performance of both vehicle types. It was found that energy consumption during the use phase had the largest environmental impact for both vehicle types. For EVs, energy consumption during use accounted for about 95% of the GWP change in the lifetime scenario, while for ICEVs, it was 35%. The reliance on non-renewable energy in 2020 had a more significant impact for EVs compared to 2050, when renewable energy is expected to play a larger role in electricity generation. Tire usage also contributed to the environmental impact, though its effect was smaller than that of energy consumption. In conclusion, the study underscores the potential of EVs to significantly reduce environmental impacts, particularly in terms of carbon emissions and air quality. However, the findings also highlight the need for further improvements in battery production, recycling, and energy production source management to minimize the overall environmental impact. Integrating renewable energy into Türkiye's electricity grid will be a critical factor in enhancing the environmental benefits of EVs. The study provides key insights into the sustainability of EV adoption in Türkiye, offering valuable guidance for policymakers and industry stakeholders in the transition to a cleaner transportation sector.