“…The sludge produced at the effluent stations has been characterized, and different thermal conversion processes have been proposed to use it (Marculescu and Stan, 2011;Marculescu, 2012;Muñuzuri, Grosso, Cortés, and Guadix, 2012;Xia, Massé, McAllister, Beaulieu, and Ungerfeld, 2012;Valta et al, 2015;Coskun et al, 2016;Ferrarez et al, 2016;Lorhi, Diener, Zabaleta, Mertenat, and Zurbrugg, 2017;Oh, and Yoon, 2017;Califano, Mongiell, and Freda, 2017;Di Maria and Micale, 2017).…”