Hydrothermal Treatment of Waste Plastics: An Environmental Impact Study

Abstract

This paper presents the attributional life cycle assessment results of a study of plastic recycling using hydrothermal treatment (HTT), a chemical recycling technology. HTT was investigated due to its potential to address current gaps in the plastic recycling system, largely due to several plastic packaging materials and formats that are currently not processed by traditional mechanical recycling technologies. As society transitions towards a net-zero-based circular economy, assessments should be conducted with a futuristic outlook, preventing costly mistakes by employing the right technologies in the right areas. The results using ReCiPe 2016 impact assessment methodology shows HTT with a GWP of 478 kg CO2 eq. per tonne can generate up to 80% reduction in climate change impacts when compared with comparable end-of-life treatment technologies whilst conserving material with the system. Additionally, the GWP could be reduced by up to 57% by changing how electricity is generated for on-site consumption. This represents a new understanding of the chemical recycling of polymers by establishing a prospective life cycle assessment study that looks to introduce a step-change in the recycling system and highlights the benefits of introducing this technology as opposed to the current model of disposal through incineration or landfill.

Separation and Characterization of Plastic Waste Packaging Contaminated with Food Residues

“…Thermochemical (or chemical) recycling, achieved via pyrolysis and closely associated processes, currently, is the most practical solution for food contact packaging and a viable alternative to mechanical recycling [11,20,21]. It can process heterogeneous mixed plastic waste freed from food residues, for example, the CMP obtained in this study.…”

“…It can process heterogeneous mixed plastic waste freed from food residues, for example, the CMP obtained in this study. Through this recycling route, polymers undergo thermochemical decomposition, producing low molecular mass compounds, which can be used to produce polymers again and/or to manufacture fuels or useful chemicals [20][21][22]. To optimise such technology, deep knowledge and understanding of how the waste packaging plastics behave at elevated temperatures are essential [11].…”

Modeling material flows through plastic recycling chains

“…In the optimistic scenario, the yield-to-monomers from advanced pyrolysis is assumed to be further increased because of further improvement in pyrolysis of FP (e.g., by adding catalyst or hydrothermal pyrolysis, etc.) (Gracia-Gutierrez et al, 2023;Ozoemena and Coles, 2023;Kusenberg et al, 2022e;Eschenbacher et al, 2022;Arena and Ardolino et al, 2022;Cardamone et al, 2022). As results, in optimistic scenarios, the yield-to-monomers from advanced pyrolysis of is assumed to increase up to 32-47%, from 15-30% in pessimistic scenarios (Table 6.5) The transfer coefficients for advanced pyrolysis is own elaboration of the authors and based on expert judgment…”

“…Higher yield-to-monomer from advanced pyrolysis because of the introduction of catalysts or hydrothermal pyrolysis, etc. (Gracia-Gutierrez et al, 2023;Ozoemena and Coles, 2023;Kusenberg et al, 2022e;Eschenbacher et al, 2022). 4 More detail information on the end market application can be found in section 6.2.2.5.…”