RWE has acknowledged that it is Europe's biggest single emitter of CO2 and therefore contributes to the acceleration of climate change.  In 2017 gas accounted for 35% of RWE’s generation capacity, followed by lignite (25%) and hard coal (17%). In addition nuclear had a share of 10% and renewables accounted for 6%. Besides the burning of gas, hard coal and lignite, RWE is involved in mining lignite which is the dirtiest of fossil fuels. RWE mines almost 100 million tons of lignite each year in its three open cast mines in North-Rhine Westfalia: Garzweiler 35 million tons; Hambach 40 million tons and Inden 22 million tons. The company also runs several lignite power plants of which three are part of Europe's five most polluting power plants.

In November 2015 Saúl Luciano Lliuya, a Peruvian farmer and mountain guide, filed a lawsuit against RWE with the help of Germanwatch. RWE's enourmous emissions threaten Raúls family, property and a large part of his home city of Huaraz.

Since 2015 the Hambach mine has become a focus of the activist alliance Ende Gelände who use civil disobedience to stop the lignite mining. RWE's Hambach mine threathens the 12,000 year old Hambacher forest, home to an oak-hornbeam woodland and 142 species of birds, 10 species of baths and rare animals protected under EU law, such as the middlespotted woodpecker, the spring frog or the dormouse. Today only 10% of the forest is left and RWE plans to clear 70ha a year to enable their Hambach mine to expand. Activists have occupied the forest and try to stop the clearance by means of tree houses.

Lignite open pit mines have swallowed entire villages and RWE has resettled 35,000 people in the last 50 years.  The villages are mostly resettled a few kilometers further including houses, churches and cementaries. The Garzweiler mine - although in operation since 2006 - has caused the resettlement of six villages and four more villages (Unterwestricht, Oberwestrich, Kuckum and Beverath) are planned to be resettled before 2028. In addition the villages of Manheim and Morschenich will be resettled before 2022 and 2024 respectively to make space for the Hambach mine which has already resettled four villages.