After my PhD in 1994 on the efficient use of energy and materials, I have worked at Princeton University and Lawrence Berkeley National Laboratory (both in the US). Since returning from the US, I have worked in consulting and since 2008 as a professor at Utrecht University. I work on energy use and energy efficiency with an a particular focus on industry and buildings, as well as the efficient use of materials and waste management. I have co-authored over 300 publications in these areas. As lead author of various IPCC reports co-recipient of the 2007 Nobel Peace Prize awarded to the IPCC.