High-yield large scale production of size-customized microplastics from biodegradable plastic mulches via variable-speed mechanical milling.

Biodegradable mulch films are increasingly used and incorporated into agricultural soils as an alternative to conventional polyethylene mulches. Although they are designed to reduce long-term plastic accumulation, they break down into microplastics before biodegradation, raising concerns about their potential ecotoxicological effects. Reliable risk assessment requires the evaluation of microplastics derived from the same mulch materials as used in the field. However, producing large quantities of microplastics from biodegradable mulch films across controlled size ranges remains challenging and often relies on costly cryogenic systems. We present a rapid, high-yield, and cost-effective method for generating microplastics from commercial biodegradable mulch films using an ultra-centrifugal mechanical mill assisted by liquid nitrogen. Microplastics in the range from <0.2 to 5 mm were produced from 600 g of BDM, with an efficiency recovery over 96% of the milled mulch. This procedure prevents polymer softening and melting during fragmentation and enables reproducible micronisation with the milling speed controlling the size distribution directly and the proportion of smaller particles increasing with higher speeds. The method allows efficient production of hundreds of grams of microplastics within hours while minimising liquid nitrogen consumption.•Cost-effective and high-yield production of microplastics from biodegradable mulch.•Speed-dependent control of particle size distribution.•An accessible alternative to dedicated cryogenic milling systems.