OICC Press International Journal of Energy and Environmental Engineering 2251-6832 10 3 (September 2019) 2019 07 04 Air gasification of digestate and its co-gasification with residual biomass in a pilot scale rotary kiln 10.1007/s40095-019-0310-3 EN C. Freda ENEA, Laboratory of Thermochemical Processes for Wastes and Biomass Valorization, Rotondella, MT, 75026, IT F. Nanna ENEA, Laboratory of Thermochemical Processes for Wastes and Biomass Valorization, Rotondella, MT, 75026, IT A. Villone ENEA, Laboratory of Thermochemical Processes for Wastes and Biomass Valorization, Rotondella, MT, 75026, IT D. Barisano ENEA, Laboratory of Thermochemical Processes for Wastes and Biomass Valorization, Rotondella, MT, 75026, IT S. Brandani Ladurner srl, Bolzano, 39100, IT G. Cornacchia ENEA, Laboratory of Thermochemical Processes for Wastes and Biomass Valorization, Rotondella, MT, 75026, IT Journal Article 2019 07 04 Abstract In this study energy recovery of digestate from a biogas plant was investigated via air gasification. Gasification tests were executed in a pilot scale rotary kiln plant having a nominal biomass feeding rate of about 20 kg/h. The equivalence ratio was varied from 0.22 to 0.39 with the goal to approach the autothermal condition. Tests were carried out for 5 h in steady state condition. Syngas composition, char and gas yields were measured. To improve the cold gas efficiency of the process, a mixture of digestate and almond shells (60:40 wt%) was gasified. Autothermal condition was reached with the mixture using equivalence ratio of 0.30 where the corresponding cold gas efficiency achieved the maximum value of 55%. The raw gas had a lower heating value of 4–5 MJ/Nm 3 . To evaluate possible improvements in the produced gas properties, in this work the effect of steam injection was also investigated.