USED DISPOSABLE NAPPIES AND EXPIRED FOOD PRODUCTS VALORIZATION THROUGH ONE- & TWO-STAGE ANAEROBIC CO- DIGESTION Konstantina Tsigkou a , Panagiota Tsafrakidou b , Alexandros Kopsahelis a , Dimitris Zagklis b , Constantina Zafiri b , Michael Kornaros a, * a Laboratory of Biochemical Engineering and Environmental Technology (LBEET), Department of Chemical Engineering, University of Patras, University Campus, Patras, GR-26504, Greece b Green Technologies Ltd, 5 Ellinos Stratiotou Str., Patras, GR-26223, Greece *Corresponding author. Tel.: +30 2610 997418; Fax: +30 2610 969584 E-mail address: kornaros@chemeng.upatras.gr (M. Kornaros) Declarations of interest: none Title Page