Greenhouse Gas emissions inventories are strategic environmental management tools that estimate emissions by specific sources in a given geographical area and timeframe. Developing an inventory is the first step in creating programs to improve air quality. This research aimed to prepare a GHG inventory and propose a management of its emissions from the activities of the Sanitation Company of Alagoas (Casal) in the Capital Unit in 2018. The methodology employed involved literature analysis to identify the most appropriate method for inventory preparation, data collection in various units of the company, interviews with managers and GHG accounting. The methodology used for the estimation was that indicated by the Brazilian GHG Protocol Program, complemented by the guidelines of the Intergovernmental Panel on Climate Change (IPCC) for the case of sewage treatment. The results of the GHG emissions inventory indicate that in 2018, Casal, Capital unit emitted 31,099.33 tCO2e, of which 86.7% (26,980.70 tCO2e) came from direct emissions, while indirect ones represented 13. 3% (4,118.63 tCO2e). The company's main sources of emissions were the sewage treatment and energy consumption categories, respectively. The results form the basis for the incorporation of GHG reduction measures in the company's strategic planning.