Plastic pollution represents one of the greatest environmental challenges of our time, as conventional plastics degrade extremely slowly in nature and accumulate in ecosystems. One possible solution is the use of biodegradable plastic materials, which are expected to break down in the environment without long-lasting negative consequences.
The aim of this thesis was to evaluate the biodegradability of two products labelled as biodegradable. One product was made from poly(3-hydroxybutyrate) (P3HB), the other from polylactic acid (PLA). Biodegradability was tested in the aquatic environment using activated sludge as the inoculum under the following conditions: in the dark, under light exposure, with the addition of nutrients, with the addition of a larger quantity of activated sludge, and with the addition of peptone as a readily biodegradable substance.
The results showed that the P3HB-based product degraded by 49.2 % in the dark, while under light exposure biodegradation increased to 57.6 %. With the addition of nutrients, the P3HB product reached 47.9 % biodegradation, with the addition of biodegradable material 47.1 %, and with the addition of activated sludge 29.2 %. The PLA-based product showed no degradation under any conditions in the dark (addition of nutrients, additions of larger quantity of activated sludge, and addition of peptone) (0 %) while under light exposure biodegradation reached 24.9 %. Additional analysis revealed that oxygen consumption in the case of PLA was due to intensive nitrification rather than biodegradation.
The results indicate that the label "biodegradable" does not necessarily mean that a material will degrade effectively in the aquatic environment, as degradation is strongly dependent on the properties of each material and varying environmental conditions.
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