Power plants that burn coal add greatly to air pollution. 燃煤的工厂也大大加重了空气污染。
Whereas some of these changes are intended mainly to increase the productivity of existing plants, completely new technologies for burning coal cleanly are also being developed. 虽然某些技术改进是渐进的，其目的只是提高现有电厂的生产率，但人们正在开发全新的清洁燃煤的技术。
