Waste-to-energy plants generate energy and they manage waste, notably municipal solid waste (MSW). Which way is best is still a matter of serious scientific research, both in a technological and in an economic-commercial sense, taking the environmental impact into account. The latter is a particular concern of the transition to a (more) circular economy, the major economic perspective launched by the European Union. The role of waste-to-energy processes in such a transition is still marred by legal problems and, even in 2017, considered a controversial subject. In this multi-disciplinary book, the state of waste-to-energy in the modern world is analyzed from the point of view of several disciplines: legal, socio- economic, commercial, and technological. [Subject: International Law, Environmental Law]