A second life for cigarette butts? A review of recycling solutions.

Trillions of cigarettes are smoked annually making cigarette butts one of the most common types of litter in the world. Due to the materials and toxic substances that they contain, this waste carries a very harmful risk for the environment and for living organisms (including humans). Only a few - barely sustainable - solutions have tried to tackle this waste and alternative solutions to landfilling and incineration are needed. Identifying the best methodological solutions and technologies for recycling this kind of waste in terms of results and applicability to real contexts would reduce the presence of dangerous materials in the environment and ecosystems and would promote the recovery of materials in line with the circular economy and sustainable development. The objective of this review was to collect and analyze the alternative solutions available in the literature for the recovery and recycling of the materials in cigarette butts, considering them as possible sources of secondary raw materials applicable to contexts of common interest. Several papers were selected and the results obtained by the authors are presented in terms of type of treatment process (physical, chemical or both), product derived (in solid, liquid or gaseous form) and its possible use in different sectors (e.g. construction, electronics, energy, chemistry and environmental protection). The main results, together with the advantages and disadvantages are highlighted and proposals for further research are outlined.