Biodegradable mulch films that are certified for soil-biodegradability (e.g. in line with EN 17033 or ISO 23517) are fully biodegradable, i.e. they are converted into CO2, H2O, and biomass. (17, 18)

This is guaranteed through the mandatory laboratory biodegradation tests required by the certification (90% mineralization absolute or relative to a positive control within 2 years’ time in soil at ambient temperature, preferably 25 °C). To be biodegraded by soil microorganisms, certified soil-biodegradable mulch films need to first disintegrate into smaller particles. These are then further biodegraded in soil, with rates depending on the environmental conditions and agricultural practices. Fragments from certified soilbiodegradable mulch films should not be confused with microplastics generated by conventional mulch films, such as polyethylene. The latter would lead to plastic accumulation in soil in case of repeated applications and incomplete collection. A recent study shows that transient particles produced by natural polymers and biodegradable materials are not to be equated with particles formed by polymers which are resistant to biodegradation. The study compared the behaviour of three materials: a certified soilbiodegradable mulch film, cellulose (natural polymer known to be biodegradable), and a non-biodegradable mulch film (HDPE). The results showed that microplastic from non-biodegradable materials persist in the environment and accumulate, while fragments generated from certified soil-biodegradable mulch films and cellulose are quickly biodegraded by microbes. (19)

(17) See OWS: Expert statement (bio)degradable mulching films, 2017, available online: films.pdf

(18) Maurizio Tosin et al.: Disintegration and mineralization of mulch films and leaf litter in soil. Polymer Degradation and Stability, Volume 179, 2020.

(19) Francesco Degli-Innocenti et al.: Analysis of the microplastic emission potential of a starch-based biodegradable plastic material, 2022, available online: https://doi. org/10.1007/s10532-023-10031-8