Abstract:

The massive production and improper disposal of waste plastics caused severe environmental pollution issues. The recycling and utilization of waste polyethylene terephthalate (PET) have received broad attention. In recent years, significant progress has been made in enzymatic depolymerization technology for waste PET, which shows potential for scaled industrial application. However, the environmental friendliness of enzymatic depolymerization compared with other recycling methods is still unclear. In this study, the environmental impact and process contribution of PET enzymatic depolymerization and alkaline hydrolysis were quantified through LCA, and the sensitivity analysis of the PET enzymatic depolymerization was constructed. The results show that the various environmental impacts of PET enzymatic depolymerization are higher than those of alkaline hydrolysis, and eight of the ten environmental indicators are more than 30% higher. Raw material pretreatment, enzyme production, and the NaOH usage in the depolymerization process are the main contributors to the environmental impact of the PET enzymatic depolymerization process. The high impact factors of alkaline hydrolysis are mainly the use of electricity and NaOH during the depolymerization process. The sensitivity analysis shows that enzyme loading rate, enzyme production, and electricity structure significantly affect the environmental benefits of enzymatic depolymerization, while the impact of solid loading rate is relatively small. Under the scenario where enzyme loading rate, enzyme production, and electricity structure are simultaneously improved, the various environmental impact indicators of PET enzymatic depolymerization are lower than or close to alkaline hydrolysis, indicating that the PET enzymatic depolymerization technology has great development potential.

Key words: polyethylene terephthalate (PET), enzymatic depolymerization, alkaline hydrolysis, life cycle assessment (LCA), wnvironmental impact, sensitivity analysis

摘要：

废塑料的大量产生和不当处置带来了严重的环境污染问题，废弃聚对苯二甲酸乙二醇酯（PET）的回收与循环利用备受关注。近年来废弃PET的酶法解聚技术取得了重大进展，已初具规模化工业应用的潜力。与其他回收方式相比，酶法解聚是否环境友好，是一个亟待探索的问题。本文通过生命周期评价（LCA）方法量化分析了PET的酶法解聚和碱性水解的环境影响及各过程阶段的贡献，并对PET酶法解聚过程进行了敏感性分析。结果表明，PET酶法解聚的各类环境影响均高于碱性水解，其中8项环境指标高出30%以上。主要是原料预处理、酶生产和解聚过程NaOH的使用在PET酶法解聚过程中造成了环境影响；碱性水解的高影响因素主要是解聚过程中电力和NaOH的使用。敏感性分析结果显示，酶负载率、酶产量和电力结构显著影响酶法解聚的环境效益，而固体负载率的影响较小。在酶负载率、酶产量和电力结构同时改善的场景下，PET酶法解聚的各类环境影响指标均低于或者接近碱性水解，说明PET的酶法解聚技术具有较大的发展潜力。

关键词: 聚对苯二甲酸乙二醇酯, 酶法解聚, 碱性水解, 生命周期评价, 环境影响, 敏感性分析