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Life cycle optimization of automobile replacement: model and application.
Hyung Chul Kim1, Gregory A Keoleian, Darby E Grande
1Center for Sustainable Systems, School of Natural Resources and Environment, University of Michigan, 430 East University, Dana Building, Ann Arbor, Michigan 48109-1115, USA.
Environmental Science & Technology
|January 1, 2004
Summary
Replacing older, inefficient cars sooner can reduce pollution. This study introduces a life cycle optimization model to determine ideal vehicle lifetimes, balancing new technology with aging vehicle impacts for cleaner transportation.
Area of Science:
- Environmental Science
- Automotive Engineering
- Operations Research
Background:
- Despite advances in new car emission controls, older vehicles and increased driving undermine progress.
- Inefficient, high-polluting older vehicles significantly contribute to environmental burdens.
Purpose of the Study:
- To develop and apply a novel life cycle optimization (LCO) model for determining optimal automobile replacement policies.
- To balance technological improvements in new vehicles against the deteriorating efficiency of older ones.
Main Methods:
- Developed a life cycle optimization (LCO) model incorporating vehicle technology improvements and efficiency degradation.
- Utilized life cycle inventories (materials, manufacturing, use, end-of-life) as inputs for the LCO model.
- Applied the LCO model to mid-sized passenger cars (1985-2020) optimizing for cumulative CO, NMHC, NOx, CO2, and energy use.
Main Results:
- Optimal lifetimes for reducing CO, NMHC, and NOx (at 12,000 miles/year) range from 3-6 years for 1980s/early 1990s models, and 7-14 years for 2000s models.
- An 18-year vehicle lifetime minimizes cumulative energy and CO2 emissions under the same annual mileage conditions.
- Shorter optimal lifetimes are correlated with higher annual vehicle mileage, particularly for pollutants like CO, NMHC, and NOx.
Conclusions:
- Vehicle replacement policies should consider the trade-offs between newer, cleaner technologies and the extended use of older vehicles.
- Policies encouraging emission control durability, retirement of high-emitting vehicles, and improved fuel economy are crucial.
- The LCO model provides a framework for informed decisions on vehicle lifetimes to mitigate environmental impact.