A groundbreaking biorefinery loop for the valorization of cigarette butts into fermentable sugars and bioethanol

Cigarette Butts are one of the most diffused and toxic waste in urban contexts. They are composed by a cellulose acetate filter, used to retain toxic compounds during the smoking of cigarette, and eventual tobacco's residues. This work had the ambitious to exploit cigarette butts in a biorefinery scheme to produce fermentable sugars and bioethanol. Cigarette butts followed different sequential operations. Deacetylation of cellulose acetate was optimized by a lipase treatment, which played an important role in the biological degradation and deacetylation of cellulose acetate. The following cellulase addition allowed the conversion of the deacetylated cellulose into fermentable sugars. In particular, the best performances were obtained with a cellulase addition of 10% of the cigarette butts, which led to a final fermentable sugars' concentration of about 12 g/L, corresponding to a cigarette butts' conversion of about 70% w/w. Then, the fermentable sugars were used as substrates for bioethanol production by three different yeasts: Metschnikowia pulcherrima MALV5, Lachancea fermentati LS16 and Saccharomyces cerevisiae EC1118. Metschnikowia pulcherrima MALV5, Lachancea fermentati LS16 achieved similar results with a bioethanol production of 2.14 and 2.44 g/L, respectively, corresponding to a fermentable sugars conversion of about 20% w/w.