Biodegradable bioplastics are presented as a tool in the fight against pollution caused by the rapid rise in the generation of plastics and inadequate waste management. These bioplastics can come from renewable or fossil sources and are characterized by their ability to decompose, through the action of microorganisms, into carbon dioxide, water, mineral salts and new biomass. Known as biodegradation, this process can occur in controlled and open environments. Composting plants and anaerobic digesters are the main examples of controlled environments, whereas soil, rivers and the sea are natural open environments.
Products based on biodegradable bioplastics must pass a series of standardized tests to demonstrate that they are able to biodegrade within a certain time in specific environments. However, for these products to effectively contribute to the reduction of plastic waste, they must be designed to biodegrade in the most applicable environment, namely, their most logical end-of-life scenario. For example, for food products such as coffee capsules, tea bags and lightweight supermarket bags, the most recommended scenarios are composting plants because this waste can be industrially managed with organic waste streams to become compost. On the other hand, products for agricultural applications such as mulch films and controlled release fertilizer coatings, whose end of life is soil, should be biodegradable in this natural environment. Likewise, products used in aquaculture and fisheries, which often end up in rivers and the sea, being biodegradable in these media, could have a lower environmental impact compared to conventional plastic products.
While biodegradation is viewed as a major advantage in the fight against plastic pollution, the ability to claim any environmental benefits is possible only when it can be proven that these biodegradable products have no negative effects on the ecosystem. This makes it important to assess any ecotoxicological effects of biodegradable plastics, given that additives, metabolites and secondary compounds may be released during product disintegration and biodegradation and may have a negative impact on the environment.
As in the case of biodegradation, ecotoxicity studies on biodegradable bioplastics should be linked to the product’s end-of-life scenario. For biodegradable products under composting conditions, ecotoxicity is assessed in compost derived from this process in terms of its potential impact on agricultural soil and, therefore, plant health. The test is performed in accordance with OECD Guideline 208[1] and Annex E of EN 13432:2001[2] standard by comparing the germination and biomass yield of monocotyledonous and dicotyledonous plants exposed during growth to different proportions of agricultural substrate and either test compost (containing biodegradation remnants of the tested product) or control compost (with no added test materials). The test compost and control compost are both obtained from a preliminary stage in which the actual composting process is simulated for a predetermined period.
