Impurities in bio-waste enter biogas and compost facilities during bio-waste treatment. The plastic fraction is usually separated and sent for incineration. This study is aimed at evaluating the quality of low density polyethylene after being exposed to anaerobic digestion, composting or both processes sequentially, in order to assess for the optimum post-processing of these plastic fractions, eventually undergoing recycling processes. The alteration in the polymer's quality was first analyzed by non-destructive optical methods, including FTIR, NIR, SEM and EDX. These tests were followed by thermal and mechanical properties' assessment.

The surface of the specimens showed signs of degradation, yet the extent of the changes was microscopic. The FTIR and NIR spectra showed higher intensities for C-H bonds in treated samples, which might be an indication of shorter polymer's chain length and/or higher chain scissoring. FTIR showed weak transmission spectral changes at regions representing C-O and O-H bonds for anaerobically digested and sequentially anaerobically digested and composted samples, indicating the existence of oxidized products, which was confirmed by the EDX analysis, where slightly higher oxygen content on the surface of specimens underwent the anaerobic digestion process was observed. However, NIR spectra did not show conforming spectra. It was accordingly concluded that the oxidized products are contaminants (residues on the specimens' surfaces), which was as well confirmed by the DSC analysis. The thermal analysis indicated a decrease in the polymer's crystallinity after being treated, where the decrease effect was the highest by anaerobic digestion, however, the mechanical properties (including tensile strength, elastic modulus and strain at break) pointed out minor quality alteration in treated samples, especially for samples underwent both processes successively. Based on the provided assessment, the general properties of LDPE plastic specimens are acceptable to be recycled, even after undergoing accelerated aging conditions, such as anaerobic digestion and composting. Further analyses are needed to evaluate plastics with additives as well as bags and films.

生物废物处理过程中，生物废物中的杂质会进入沼气和堆肥设施。通常将塑料部分分离并送去焚化。这项研究旨在评估低密度聚乙烯在经历厌氧消化，堆肥或依次进行这两个过程后的质量，以便评估这些塑料级分的最佳后处理，并最终进行回收利用。首先通过无损光学方法（包括FTIR，NIR，SEM和EDX）分析聚合物质量的变化。这些测试之后进行热和机械性能评估。

样品的表面显示出降解的迹象，但是变化的程度是微观的。FTIR和NIR光谱显示在处理过的样品中CH键的强度更高，这可能表明较短的聚合物链长和/或较高的剪叉性。FTIR在厌氧消化和顺序厌氧消化和堆肥的样品中代表CO和OH键的区域显示出较弱的透射光谱变化，这表明存在氧化产物，这通过EDX分析得到证实，其中样品表面的氧含量略高观察到厌氧消化过程。但是，NIR光谱未显示出符合的光谱。因此得出的结论是，氧化产物是污染物（样本表面上的残留物），DSC分析也证实了这一点。热分析表明，处理后聚合物的结晶度降低，其中厌氧消化的降低效果最大，但是机械性能（包括拉伸强度，弹性模量和断裂应变）表明处理后样品的质量变化较小，尤其是对于样品先后经历了两个过程。根据提供的评估结果，即使经历了加速老化条件（例如厌氧消化和堆肥），LDPE塑料样品的一般性能还是可以回收的。需要进一步分析以评估具有添加剂的塑料以及袋子和薄膜。处理后的结晶度，其中厌氧消化的减少效果最大，但是机械性能（包括抗张强度，弹性模量和断裂应变）表明处理后的样品质量变化不大，特别是对于连续进行这两个过程的样品。根据提供的评估结果，即使经历了加速老化条件（例如厌氧消化和堆肥），LDPE塑料样品的一般性能还是可以回收的。需要进一步分析以评估具有添加剂的塑料以及袋子和薄膜。处理后的结晶度，其中厌氧消化的减少效果最大，但是机械性能（包括抗张强度，弹性模量和断裂应变）表明处理后的样品质量变化不大，特别是对于连续进行这两个过程的样品。根据提供的评估结果，即使经历了加速老化条件（例如厌氧消化和堆肥），LDPE塑料样品的一般性能还是可以回收的。需要进一步分析以评估具有添加剂的塑料以及袋子和薄膜。特别是对于样品先后经历了两个过程。根据提供的评估结果，即使经历了加速老化条件（例如厌氧消化和堆肥），LDPE塑料样品的一般性能还是可以回收的。需要进一步分析以评估具有添加剂的塑料以及袋子和薄膜。特别是对于样品先后经历了两个过程。根据提供的评估结果，即使经历了加速老化条件（例如厌氧消化和堆肥），LDPE塑料样品的一般性能还是可以回收的。需要进一步分析以评估具有添加剂的塑料以及袋子和薄膜。