Life Cycle Optimization Methods for Enhancing the Sustainability of Design and Policy Decisions

A critical question regarding the life cycle design and management of any product system is, ?What is its optimal service life?? The Center for Sustainable Systems at the University of Michigan has developed life cycle optimization (LCO) methods and models to evaluate optimal service life and asset management decisions from energy, emissions, cost and policy perspectives. This LCO model is based on a dynamic programming method with inputs derived from life cycle assessment (LCA). From an environmental perspective, this is a particularly complex question to resolve for product systems with nonlinear use phase burdens and given uncertainty in technology improvement trajectories. In the case of automobiles, household appliances, and computers, there exist multiple tradeoffs between maintaining an existing model and replacing it with one that is more efficient. The efficiency gain from model replacement should exceed the additional resource investments required to produce the new model.

The life cycle optimization model has also been applied to infrastructure systems that require large capital investments with maintenance costs and have long service lives. Road pavement poses significant modeling challenges given the interactions between pavement and vehicle systems. Models are required to simulate congestion related to road construction events, road deterioration behavior, road roughness effects on fuel economy, and vehicle technology improvements. Here optimization is used to determine asset management decisions including budget allocation decisions, pavement material selection and the timing and frequency of rehabilitation events.

Optimization is an important technique to add to the life cycle modeling toolkit for informing design and policy decisions which will be demonstrated with several applications. LCO has been applied to study automobiles, refrigerators, clothes washers air conditioners and highway infrastructure. Results from these studies will be highlighted and general principles for enhancing sustainability will be presented.