Energy Collective: If I asked you to think of renewable energy what comes to mind? I imagine it is skyscraper-sized wind turbines, solar panels on suburban roofs or massive hydro-electric dams. You probably do not think of burning wood or converting crops to liquid fuel to be used in cars. Yet throughout the world bio-energy remains the biggest source of renewable energy. In fact its growth in the last decade has been greater than or similar to that from wind and solar in most places, and those places include the European...