Replication data for: Microplastic degradation during hydrothermal carbonization

Microplastics (MPs) have been recently identified as harmful micropollutants which are a major threat for the environment and animal and human health. Microplastics, below 5 mm, are the result of the degradation of primary (larger) and secondary (transformed from primary) materials whose shape, size, type, and composition significantly differ. The most frequently found polymers in microplastics are polyamide (PA), polyethylene (PE), polyether sulfone (PES), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). The small size, insoluble properties, bioaccumulation potential and resistance to degradation of MPs stimulate their transfer into the environment mainly through wastewater from industries using polymers, irrigation, road transport or human activities. Consequently, wastewater treatment plants produce sewage sludge containing accumulated MPs and, if used as fertilizer (36.6% of sewage sludge disposal in Poland), it may contaminate plants and enter the food chain causing health problems for animals and humans. Up to now, there has not been a specific comprehensive law in the EU concerning microplastics, although there are several laws related to this issue. However, in October 2023, EU adopted several initiatives on MPs and proposed to restrict the microplastics intentionally added to products under the chemical legislation REACH, and provided the proposal of a regulation preventing pellet losses to reduce microplastic pollution. Evidently, the problem has been widely discussed and is under consideration. Therefore, new developing technologies for treating biosolids, digestate from wastewater treatment plants, are focused not only on the proper management of sewage sludge, but also on the removal and degradation of major micropollutants such as microplastics. Hydrothermal carbonization (HTC) has proved to be an efficient method in terms of the problematic properties of biosolids, which are a suitable feedstock for this method due to their high moisture content (c.a. 80%) and organic origin. The process significantly improves dewaterability, while decreasing exploitation costs, and it ensures adequate disinfection by applying a high range of temperature, which is required to deactivate viruses and pathogens. The degradation of microplastics from biosolids by hydrothermal carbonization has not, so far, been widely studied. There are only a few reports which are mainly focused on the shape, size and type of microplastics due to the analytical problem of detection and identification of microplastics. Therefore, scientific knowledge of the transformation mechanism of microplastic degradation and the degree of their removal from biosolids by the hydrothermal carbonization method is essential to fulfil this gap.