2.1. Introduction

Sustainability issues are complex, and understanding their interactions with equally complex engineered systems is best done through well-structured analysis frameworks. Risk-based frameworks have traditionally been used in the characterization and prioritization of environmental issues, and the first section of this chapter describes those frameworks. Increasingly, however, life-cycle frameworks are gaining prominence as a means of characterizing and understanding sustainability. The second major section of this chapter introduces life-cycle frameworks and their uses.