This study aimed at developing a simple tool for improving the management of gaseous emissions in UASB-based sewage treatment plants (STPs), considering different scenarios for the management of sludge, biogas and gaseous emissions (especially sulfide and methane). For small STPs (<10,000 inhab.), simple alternatives for the use of biogas were considered (e.g. for excess sludge hygienization and household usages). For medium- (>10,000; <100,000) and large-scale (>100,000 inhab.) STPs, other biogas uses were considered, such as in sludge dryers, boilers or combined heat and power engines for electricity generation and heat recovery. All these possibilities were grouped in an interactive spreadsheet containing an extensive database of factors that affect gaseous emissions and energy balance in STPs. The tool can be important for decision makers choosing the best gaseous emissions management practices in UASB-based STPs. Carbon footprint should be the main decision factor when evaluating alternatives for the management of gaseous emissions.