The group focuses on building tools to reduce the environmental impacts of energy systems. One focus is on understanding greenhouse gas emissions (GHGs) from fossil energy systems. Also, we build optimization tools to improve the environmental and economic performance of energy systems. Our approach includes building engineering-based bottom-up life cycle assessment (LCA) models to generate rigorous estimates of environmental impacts from energy extraction and conversion technologies. In optimization areas, we focus on renewable-fossil hybridization and integration.