A promising approach to monitor microplastic masses in composts
Source: BAM
Plastics in the environment are now found and detected all over the world. This applies to both large macroplastics and small plastic fragments (microplastics). Macroplastics include particles from 5 mm up to complete products such as plastic bottles, whereas microplastics include plastic components such as fibers and particles with a size of 1 µm to 1 mm (ISO/TR 21960:2020). Source identification is often difficult to accomplish, as plastic inputs are very diverse. However, compost is considered a possible entry pathway into the environment. The source materials, such as the contents of organic waste garbage cans from private household waste, are often contaminated with plastics due to inadequate waste separation. Although sorting out plastic waste during the production process in the composting plant is very effective, some plastics remain undetected. According to the German Fertilizer Ordinance, the total plastic content at the end of the production process may not exceed 0.5%. However, only plastic particles and fragments larger than 1 mm are considered, which means that the microplastic content is not taken into account.
This is also due to the complex analysis required to detect and quantify these small particles. The patented thermal extraction desorption gas chromatography/mass spectrometry (TED-GC/MS) method developed at BAM enables not only the detection but also the quantification of microplastics in terms of mass content and concentration. Short measurement times also enable a high sample throughput, which is essential for monitoring purposes and process control. However, it turned out that the analysis of microplastics was not the only thing that needed to be considered and developed. Each laboratory sample is only representative if it has the same percentage composition of individual substances as the original sample to be analyzed. In order to obtain a representative distribution and quantification of microplastics and large microplastics (1-5 mm), a concept was developed in cooperation with the Federal Environment Agency (UBA), ranging from the correct sampling of the pile, density separation as sample preparation in the laboratory to the optimization of the analytical method. It was shown that holistic investigation concepts such as this are necessary in order to receive uniform and representative results of the microplastic content. The developed method of density preparation as sample preparation has since become established and is now being incorporated into (international) standardization.
A promising approach to monitor microplastic masses in composts.
Wiesner Yosri, Bednarz Marius, Braun Ulrike, Bannick Claus Gerhard, Ricking Mathias, Altmann Korinna
Frontiers in Environmental Chemistry, Volume 4, 2023