Considering that 80 % of marine litter is made of plastic, the EU adopted in 2019 the Single Use Plastic Directive (SUP). It targets ten single use plastic items representing 70 % of the marine litter.

Cigarette butts made of cellulose acetate is among the top ten. Therefore, there is an interest in replacing cellulose acetate filters by a non-plastic alternative, such as, for instance, paper.

As the use of non-plastic cigarette filters are growing, it is important to have characterisation methods in order to understand their physical structure and how it compares to a cellulose acetate one.

Optical microscopy, scanning electron microscopy (SEM) and X-Ray tomography were used in this study. Optical microscopy allows the visualizing of the filter rod and cigarette butt appearance post consumption. The paper crimping process used for the filter rod formation, especially pitch size and paper expansion, can also be characterised by this technique. SEM allows deep analysis of fibres and paper cross-section appearance. Today, several types of cellulosic filter media can be used. Optical and SEM microscopy allow the differentiation of these different types.

The cigarette filter 3D structure can be determined with X-Ray tomography that shows the distribution of the filtering media inside the filter. Crimped paper is not homogeneously distributed in a filter rod with the presence of channels. 3D tomography can look inside the filter rod and it highlights that the channels are discontinuous all along the filter, which contributes to the higher paper filter smoke/aerosol retention. By changing the resolution of 3D tomography, we can obtain more in depth information about the distribution of cellulosic fibres inside the filter.

The above three imaging techniques are complementary and, when selected properly, can address various targets: visual appearance, crimping characterisation, fibre composition or scientific understanding.