Researchers from Seoul National University developed a one-step method to prepare a carbon material (which they call NCF) from used cigarette filters.

They used the NCF to create supercapacitor electrodes - which exhibit a better rate capability and higher specific capacitance compared to conventional activated carbon - and even perform better than graphene or carbon nanotube electrodes!

http://www.graphene-info.com/used-cigarette-filters-turned-supercapacitor-electrodes-outperform-graphene-based-ones