1. 1Center for Industrial Ecology, Yale School of the Environment, Yale University, New Haven, Connecticut, USA; email: y.yao@yale.edu
2. 2Chemical and Environmental Engineering, Yale School of Engineering and Applied Science, Yale University, New Haven, Connecticut, USA
3. 3Yale School of the Environment, Yale University, New Haven, Connecticut, USA
4. 4International Institute for Applied Systems Analysis, Laxenburg, Austria