Deacetylation Processing of Waste Cigarette Butts for High-Titer Bioethanol Production toward a Clean Recycling Process

Proper disposal of large-quantity waste cigarette butts (WCBs) is of great importance for alleviating marine and land pollution, but it has been challenged by their complex compositions and toxic compounds contents. This work showed a technically feasible way to valorize WCBs through bioethanol production with high titers. Three deacetylation solvent systems, i.e., aqueous alkali, emerging alkali ethanol organosolv, and alkali deep eutectic solvent, were assessed for their abilities to produce high-purity and digestible cellulose. Results showed the acetyl groups content in WCBs after various deacetylation processes was significantly decreased from 46.65% to similar to 4.66%, corresponding to the cellulose content increasing from 54.94% to similar to 94.61%. It was proposed that the dual function of acetyl groups removal and cellulose deconstruction of these deacetylation solvent systems was responsible for enriching cellulose and enhancing its enzymatic accessibility, which allowed the subsequent facile simultaneous saccharification and fermentation (SSF) process to be operated at 20% (w/v) high solids loading. When the overall mass balance was traced during the deacetylation and SSF process based on 100 g of WCBs, a maximum bioethanol production of 25.4 g with a high titer of 76.5 g L-1 could be obtained. This work showed that a facile deacetylation process using alkaline solvent systems was promising for clean recycling of WCBs and also could provide useful technological information for valorizing other waste cellulose ester plastics.