Technical and Engineering Challenges in Scaling Up Microwave-Assisted Pyrolysis of Waste Plastics
- 1Department of Chemical and Biomolecular Engineering
- 2University of Houston
- 3E&T Division, Electrotherm (India) Ltd.,, Survey No. 72, Palodia, Ahemdabad, Gujrat, India, 382115
Abstract
Microwave‑assisted pyrolysis (MAP) has emerged as a promising thermochemical route for converting waste plastics into fuels, chemicals, and carbon materials, offering fast volumetric heating, lower apparent reaction temperatures, and distinctive product selectivity compared with conventional pyrolysis. At present, however, MAP of plastics is still largely confined to laboratory and bench‑scale batch reactors, corresponding mainly to laboratory and pilot technology readiness levels, and the engineering barriers to continuous, large‑scale operation remain poorly understood. This review critically examines the technical and engineering challenges that hinder the scale‑up of MAP for plastic waste valorisation, complementing existing chemistry‑focused reviews that emphasize process parameters and product yields. The key scale‑up barriers discussed include: (i) electromagnetic field non‑uniformity and limited microwave penetration depth in larger cavities, leading to hot spots, thermal runaway, and variable product quality; (ii) design and operation of continuous feeding systems for thermoplastic melts and mixed solid feeds, including mechanical integration of screw feeders, conveyors, and augers in high‑temperature microwave environments; (iii) susceptor selection, durability, and in‑process management (SiC, activated carbon, in‑situ char); (iv) real‑time temperature measurement and process control under microwave irradiation; (v) feedstock variability and the heterogeneous dielectric behaviour of post‑consumer plastic streams; (vi) downstream product quality requirements and constraints for refinery and steam‑cracker integration; and (vii) the current status of coupled multiphysics modelling (electromagnetic–thermal–CFD–reaction) and emerging digital‑twin approaches for reactor and process scale‑up. Reported techno‑economic analyses and life‑cycle assessments suggest that MAP can reduce energy use and greenhouse‑gas emissions relative to conventional plastic pyrolysis under favorable conditions, but robust pilot‑scale datasets and validated process models remain limited. By systematically mapping these unresolved engineering challenges onto recent advances in reactor design, susceptor engineering, process monitoring, Multiphysics simulation, and industrial pilot lines, this review proposes a lab‑to‑pilot‑to‑industrial roadmap for plastic MAP. It identifies priority research directions to advance MAP toward commercial deployment and clarifies its potential role within a broader circular economy framework for plastic waste.
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BibTeX
@misc{tiwari2026technical,
title = {{Technical and Engineering Challenges in Scaling Up Microwave-Assisted Pyrolysis of Waste Plastics}},
author = {Mahendra Tiwari and Chhavi Shukla and Mohammad Moniruzzaman and Joeseph B. Powell},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15007987/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15007987/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Technical and Engineering Challenges in Scaling Up Microwave-Assisted Pyrolysis of Waste Plastics
AU - Mahendra Tiwari
AU - Chhavi Shukla
AU - Mohammad Moniruzzaman
AU - Joeseph B. Powell
PY - 2026
DA - 2026/09/02
PB - ChemRxiv
DO - 10.26434/chemrxiv.15007987/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15007987/v1
AB - Microwave‑assisted pyrolysis (MAP) has emerged as a promising thermochemical route for converting waste plastics into fuels, chemicals, and carbon materials, offering fast volumetric heating, lower apparent reaction temperatures, and distinctive product selectivity compared with conventional pyrolysis. At present, however, MAP of plastics is still largely confined to laboratory and bench‑scale batch reactors, corresponding mainly to laboratory and pilot technology readiness levels, and the engineering barriers to continuous, large‑scale operation remain poorly understood. This review critically examines the technical and engineering challenges that hinder the scale‑up of MAP for plastic waste valorisation, complementing existing chemistry‑focused reviews that emphasize process parameters and product yields. The key scale‑up barriers discussed include: (i) electromagnetic field non‑uniformity and limited microwave penetration depth in larger cavities, leading to hot spots, thermal runaway, and variable product quality; (ii) design and operation of continuous feeding systems for thermoplastic melts and mixed solid feeds, including mechanical integration of screw feeders, conveyors, and augers in high‑temperature microwave environments; (iii) susceptor selection, durability, and in‑process management (SiC, activated carbon, in‑situ char); (iv) real‑time temperature measurement and process control under microwave irradiation; (v) feedstock variability and the heterogeneous dielectric behaviour of post‑consumer plastic streams; (vi) downstream product quality requirements and constraints for refinery and steam‑cracker integration; and (vii) the current status of coupled multiphysics modelling (electromagnetic–thermal–CFD–reaction) and emerging digital‑twin approaches for reactor and process scale‑up. Reported techno‑economic analyses and life‑cycle assessments suggest that MAP can reduce energy use and greenhouse‑gas emissions relative to conventional plastic pyrolysis under favorable conditions, but robust pilot‑scale datasets and validated process models remain limited. By systematically mapping these unresolved engineering challenges onto recent advances in reactor design, susceptor engineering, process monitoring, Multiphysics simulation, and industrial pilot lines, this review proposes a lab‑to‑pilot‑to‑industrial roadmap for plastic MAP. It identifies priority research directions to advance MAP toward commercial deployment and clarifies its potential role within a broader circular economy framework for plastic waste.
ER -