Microplastics ending up in nature as a result of end-of-life processes for plastic packaging is a serious environmental concern, and was addressed in the Packnoplast project through sampling at three sites: one biogas facility in Norway and two thermoplastic recycling plants, one in Norway and one in The Netherlands.
The amounts of microplastics ending up in soil from biogas digestate was estimated to represent 0.4-2 mg/kg soil per year if 6 t/daa of biogas digestate is used as fertilizer. Food packaging is estimated to represent 75% of this. The amounts of microplastics measured are significant, but too small to affect soil properties even on a time-scale of decades. The risk of adverse effects on soil quality, plant growth or soil organisms seem very low at the current predicted rates of plastic inputs to soil. Since plastics are virtually non-degradable, they are still prone to accumulate in soil, and waste streams recycled to soil need to address and prevent plastic contamination even better than today.
Thermoplastic recycling plants are handling large amount of plastic, and during processes in the plant, microplastic are generated. Concentrations of microplastic particles varied from 7 to 51 particles per liter in the effluent water from the two plants. Discharges of effluent water are often through the sewer system and/or into a water body. Today regulations regarding discharges of microplastic are missing. Sand filter treatment of the effluent water was a promising treatment technique to remove the microplastics. Background concentrations of microplastic, comparable to pristine areas, were found in blue mussels sampled outside the thermoplastic recycling plant in Norway. Knowledge about the risk imposed by microplastics to the aquatic environment is today not known.