Mining projects, especially lignite opencast exploitation, are usually neglected by a society. The social acceptance for development of new lignite deposits and for new lignite-based power plants is very low. These is caused by impression of "enormous environmental impact" of extractive industry usually recalled by environmental organizations. The paper presents the discussion with arguments used by opponents of lignite mining. As a background for discussion the polish energy production and demand was described. The efficiency improvement of power generation, the environment protection measures implemented in lignite power plants and successful reclamation measures in opencast mines were recalled. The contribution of lignite industry for regional prosperity and live standard of residents was shown. Due to increasing nature protection above the polish lignite deposits many of them became not accessible. In consequence the polish lignite reserves should be verified. As an example for the analyze a case study, basing on one lignite deposit, was presented. In summary the need of lignite deposits protection due to, guaranteed by polish law, sustainable development was stressed.