Display omitted •Emission characteristics were studied during co-combustion in a grate furnace.•Ambient air quality study was compared with gaseous emissions after combustion.•Emission observed during the combustion showed PM as 580–1432 mg/Nm3.•Emitted SO2 (55–147 mg/Nm3) & NOX (7.5–24 mg/Nm3) were within the prescribed limit.•Monitoring and control system can be adopted to meet the standard limits. Distillery sludge and coal co-combustion are favorable energy recovery options which also help to overcome the individual feed sample disadvantages. The emission of PM, SO2, NOx, HCl, HC, CO and CO2 was studied during the co-combustion experiments along with monitoring of the ambient air quality at the experimental site. The combustion of coal and sludge samples was studied and the results showed that by increasing the distillery sludge mixed coal ratio from 20%, 30% and 40% (wt./wt.%), the emission values reduced. Air borne PM and gaseous pollutants did not exceed the standard limit for ambient air. The results for PM were observed within the range i.e. 580–1432 mg/Nm3. Similarly, SO2 and NOx emissions were 55–147 and 7.5–2.4 mg/Nm3 of all the substrate combinations. To regulate the flue gas composition and monitor the emitted gases, it is necessary to pass it through a proper control systems.