A carbon footprint is currently one of the widely distributed methods for assessing an anthropogenic impact on environmental systems. Despite a long history of such estimations, there is no unified model for its calculation. Existing approaches include different components of artificial processes as sources of greenhouse gas emissions. On the example of RUDN University (Moscow, Russia), the article presents the results of applying different calculation methodologies. The use of these approaches gives a difference of up to 2.5 times. At the same time, greenhouse gas absorption is out of consideration. Thus, the relevance of the issues of carbon footprint assessment requires the development of detailed methods for assessing the role of urban ecosystems and the selection of good accounting algorithms for all activities of organizations considered as objects of analysis in terms of greenhouse gas emissions. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.