Whether you are interested in sustainable development of the planet or simply how to save energy in the home, I highly recommend this book: "without the hot air". Written by David MacKay, it can be downloaded for free. It's easy to read and provides a practical, numerical consideration of declining natural resources and climate change.
My final-year undergraduate project was based on the extrusion-spheronisation of pharmaceutical pastes.
My PhD research area would have involved working on chemical looping within the Sustainability group of the Department of Chemical Engineering, University of Cambridge. Chemical looping can improve power station efficiency or act as a carbon capture technique, decreasing the amount of carbon dioxide released into the atmosphere and instead sequestering (storing) it in a manner such that it cannot contribute to global warming.
However, I have put the PhD plans on hold indefinitely at the moment.