Assessing bioplastics biodegradability by standard and research methods: Current trends and open issues

Bioplastics are currently and increasingly used as substitutes of conventional plastics; furthermore, they are mainly utilised in order to cope with problems related to plastic-based pollution. Certified international standard methods identify the criteria a bioplastic must comply with in order to be labelled as compostable and/or biodegradable. In addition, this is particularly the case when operating under the conditions that are expected in full-scale waste facilities. However, biodegradation in natural environments occurs under a manifold of different conditions, such that the aim of research studies is to estimate the extent to which a bioplastic can biodegrade under simulated natural conditions. For this reason, specific indexes are used to quantitatively estimate the degree of degradation. In the present paper, a description of the standard methods, research methods, and the indexes used to assess the biodegradability of bioplastics under different environmental conditions is provided. By summarising the results obtained by this study, it can be concluded that: (i) biopolymers claimed as biodegradable bioplastics may not degrade in full-scale plants due to the fact that the process conditions present in industrial waste treatment plants cannot completely reproduced at lab-scale; (ii) the static conditions set by the standard methods are not representative of the dynamic processes that occur in natural or industrial environments; and (iii) experimental tests are difficult to compare to one other due to the differences in the multitude of matrixes that can be used (i.e., inocula, soils, and biopolymers).