Yi Liu was born in 1975 in China. He received his bachelor's degree and PhD at the Department of Environmental Sciences and Engineering at Tsinghua University in July 1999 and July 2004, respectively. In March 2001 he joined the Environmental Policy Group at Wageningen University in the Netherlands and obtained his second doctorate in May 2005. He came to the International Institute for Applied System Analysis in Austria in August 2006 and did a postdoctoral research on global phosphorus cycle. He is currently a lecturer at the Department of Environmental Sciences and Engineering, Tsinghua University. Dr. Liu's main research subjects include environmental system analysis, strategic environmental assessment, and material flow analysis.