The term 'Cologne Complaint' refers to a legal complaint filed in the German city of Cologne in 2011. The complaint was filed by a group of citizens who were concerned about the environmental impact of a nearby coal-fired power plant. The complaint was successful, and the plant was shut down in 2013. The acronym ACH stands for 'Anwohnerinitiative Cologne-Hohenlind, ' which translates to 'Citizen Initiative Cologne-Hohenlind.' This was the name of the group that filed the complaint.