Cecon Victor S, Curtzwiler Greg W, Vorst Keith L
Polymer and Food Protection Consortium, Iowa State University, 536 Farmhouse Lane, Ames IA, 50011, USA; Department of Food Science and Human Nutrition, Iowa State University, 536 Farmhouse Lane, Ames IA, 50011, USA.
Polymer and Food Protection Consortium, Iowa State University, 536 Farmhouse Lane, Ames IA, 50011, USA; Department of Food Science and Human Nutrition, Iowa State University, 536 Farmhouse Lane, Ames IA, 50011, USA.
Waste Manag. 2023 Sep 10;171:313-323. doi: 10.1016/j.wasman.2023.09.002.
Plastic recycling rates are still low in the United States (U.S.), with less than 10% of municipal solid waste (MSW) plastic being recycled. Most unrecycled plastics are identified by Resin Identification Codes (RIC) from #3-7, which are commonly destined for landfill or waste-to-energy facilities (WTE). Therefore, the composition and quality of outbound bales containing #3-7 plastics were assessed to understand the potential to increase recycling rates. Three bales were sourced from three different Material Recovery Facilities (MRFs) located in the United States. Each bale was manually sorted and characterized for quality and performance via multiple plastic characterization techniques. Considerable differences in bale composition were observed between MRFs, which correlated with the technology used by each MRF in the sorting process. The differences were substantial in the residual levels of poly(ethylene terephthalate) (PET) and high-density polyethylene (HDPE), which are highly desired for mechanical recycling processes and not expected in #3-7 plastics bales. Traditional recycling processes including washing, extrusion, and injection molding of the sorted material were employed prior to the physical, thermal, and molecular characterization. Despite differences in bale composition by plastic type, some polymer properties were similar across MRFs. This research suggests that landfill-diverted mixed plastic waste can be utilized in the mechanical recycling of currently unrecycled materials, as processes can be designed to work with consistent polymer properties. It also highlights the need to upgrade the sorting systems to prevent waste feedstocks, which can be recycled with current technologies, from contaminating other plastic streams or reach landfills.
美国的塑料回收率仍然很低，城市固体废物（MSW）中只有不到10%的塑料被回收利用。大多数未回收的塑料通过树脂识别码（RIC）从3号到7号进行识别，这些塑料通常最终被运往垃圾填埋场或垃圾转化能源设施（WTE）。因此，对含有3号至7号塑料的外运捆包的成分和质量进行了评估，以了解提高回收率的潜力。从美国的三个不同的材料回收设施（MRF）获取了三捆塑料。每捆塑料都经过人工分拣，并通过多种塑料表征技术对其质量和性能进行了表征。不同MRF之间观察到捆包成分存在显著差异，这与每个MRF在分拣过程中使用的技术相关。聚对苯二甲酸乙二酯（PET）和高密度聚乙烯（HDPE）的残留水平差异很大，而这些在机械回收过程中是非常需要的，并且在3号至7号塑料捆包中并不预期会出现。在进行物理、热学和分子表征之前，对分拣后的材料采用了包括洗涤、挤出和注塑在内的传统回收工艺。尽管不同类型塑料的捆包成分存在差异，但一些聚合物性能在不同MRF之间是相似的。这项研究表明，从垃圾填埋场转移出来的混合塑料废物可用于目前未回收材料的机械回收，因为可以设计出与一致的聚合物性能相适应的工艺。它还强调了升级分拣系统的必要性，以防止那些可以用现有技术回收的废原料污染其他塑料流或进入垃圾填埋场。
