Biodegradability of biodegradable mulch film : A review of the scientific literature on the biodegradability of materials used for biodegradable mulch film

This report presents the findings of a desk study, commissioned by NRK-V and executed independently by WFBR. The objective of the desk study is to provide insight in the information available in the public and scientific literature regarding the biodegradability of biodegradable mulch film for use in agriculture and horticulture. Biodegradability of plastic describes the potential to undergo biodegradation in a suitable environment. Biodegradation does not only depend on the chemistry of the polymer, but also on the presence and activity of the biological systems involved in the process. This means that biodegradability in soil can be different from biodegradability in industrial composting conditions. The biodegradation of plastic is defined as its complete microbial utilization, resulting in its conversion to CO2, (and/or CH4), water and biomass by the metabolic activity of microorganisms. Not all materials labelled ‘biodegradable’, ‘oxo-(bio)degradable’ or ‘compostable’ will actually biodegrade at sufficient rate at ambient temperatures in soil to prevent accumulation of plastic (residues) in the field. Typically, mulch films are produced by combining polymeric feedstocks with other components (via master batches), such as processing aids, plasticizers and colorants, which are then further processed through extrusion into film. Regarding biodegradability and environmental fate it is important to consider not only the polymeric constituents, but all components that are used to produce the mulch film. In this report the biodegradability is discussed of the main polymeric constituents commonly employed for biodegradable mulch film. These include (thermoplastic) starch and several polyesters, including poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene succinate) (PBS), poly(lactic acid) (PLA) and poly(hydroxy alkanoate) (PHA). It is important to realize that general statements regarding the biodegradability of these polymers are not possible, because variations of comonomer composition, molar mass, etc. within a polymer family, can have substantial effects on physical properties and biodegradation behaviour. Polymer grades that have passed the biodegradability requirements as stipulated in EN 17033 are likely to actually biodegrade to CO2 and water (and biomass) at sufficient rate when applied in agri- or horticulture in the Netherlands. Certification according to ‘DIN geprüft Biodegradable in soil’, ‘OK Biodegradable SOIL’, ‘OK compost HOME’ and ‘DIN Geprüft Home compostable’ is considered a reliable confirmation that fulfilment of the biodegradability requirements of EN 17033 has been demonstrated.