This lecture discusses the comparison of various environmental policy instruments aimed at addressing excess harmful emissions. It begins by identifying the problem of emissions and the need for optimal abatement solutions, which require the participation of individual emitters. The instructor outlines different approaches, including voluntary measures, public investments, command-and-control regulations, and economic instruments such as taxes and tradable quotas. The effectiveness of these instruments is evaluated based on criteria such as environmental effectiveness, cost-efficiency, equity, and political feasibility. The lecture emphasizes the importance of a mixed approach to environmental policy, combining various instruments to enhance effectiveness and efficiency while considering the administrative costs involved. The discussion also touches on the challenges of assessing voluntary approaches and the implications of compliance and participation motives among emitters. Overall, the lecture provides a comprehensive overview of the instruments available for environmental policy and their respective impacts on emission reduction efforts.