Climate change and environmental degradation are certainly the overriding issues of the 21st century and represent two of the most complex challenges humanity has ever faced. Environmental technologies present unique opportunities to mitigate climate change and preserve the environment. However, barriers to the diffusion of environmental technologies are numerous. This analysis focuses on intellectual property rights and aims at determining how to optimize environmental technology diffusion in the presence of intellectual property constraints. Indeed, intellectual property rights appear both as incentives to innovation and diffusion, as well as legal and financial barriers to diffusion. The book adopts a transversal approach and offers to assess the legal mechanisms made available by public international law to optimize environmental technology diffusion in the presence of intellectual property constraints, namely: trade-related incentives, the framework provided by multilateral environmental agreements, as well as the diffusion of environmental technology by means of exception to and limitation of intellectual property rights. The study's added value lies not only in the adopted transversal approach to the question, but equally in the assessment of numerous case studies, as well as in the parameters and criteria suggested with respect to a variety of legal approaches. In addition, the analysis assesses some legal tools that have, to date, received little attention from scholars and researchers, such as patent markets or fast-track patent application programmes.