(2022) Journal of Hazardous Materials_Disposal of plastic mulching film through CO₂-assisted catalytic pyrolysis as a strategic means for microplastic mitigation

Jung J.-M., Cho S.-H., Jung S., Lin K.-Y.A., Chen W.-H., Tsang Y.F., Kwon E.E.

(Elsevier B.V.) Journal of Hazardous Materials ISSN: 3043894 Vol.430 Issue. Article No.128454 DOI: 10.1016/j.jhazmat.2022.128454

Conventional disposal processes (incineration and landfilling) of agricultural plastic wastes release harmful chemicals and microplastics into our ecosystems. To provide a disposal platform not releasing harmful chemicals, pyrolysis of a representative agricultural plastic waste was proposed in this study. Spent plastic mulching film (SMF) was used as a model waste compound. To make pyrolysis process more environmentally benign, CO₂ was used as a raw material in pyrolysis of SMF. H₂ and hydrocarbons were produced from pyrolysis of SMF under the inert (N₂) and CO₂ conditions, because SMF is composed of polyethylene. To enhance conversion of hydrocarbons into H₂, catalytic pyrolysis of SMF was conducted over Ni/SiO₂. Compared to non-catalytic pyrolysis, total concentration of pyrolytic gases was enhanced up to 3.1 and 11.3 times under N2 and CO₂ conditions, respectively. The gas phase reactions between CO₂ and hydrocarbons led to formation of CO, which enhanced production of pyrolytic gases under the CO₂ condition. Moreover, gas phase reactions resulted in less production of pyrolytic oil from CO₂ condition (15.9 wt%) in reference to the N₂ condition (22.6 wt%). All experimental results confirmed that CO₂ and SMF can be used as useful feedstocks to produce value-added products. Environmental Implication: Plastic waste used from a sector of agriculture is incinerated or/and landfilled, generating hazardous microplastic and volatile compounds into the environment. Thus, an environmentally friendly process for plastic waste materials in the agricultural industry is required. This study converted a spent plastic mulching film (SMF), broadly used for plastic greenhouse, into value-added syngas through catalytic pyrolysis. CO₂ was used as a reactant. We found that concentration of CO₂ was key to improve syngas formation from pyrolysis of SMF. Thus, this study suggested that CO₂/SMF are used as useful feedstocks through catalytic pyrolysis, while they were previously discarded as waste materials © 2022 Elsevier B.V.

This work was supported by the Environment and Conservation Fund of the Hong Kong Special Administrative Region Governmen t (No. 2020-76 ), SKLMP Seed Collaborative Research Fund (No. SCRF/0026 ), and the Dean’s Research Fund (No. IRS-4 RG30/2021-2022R ) of The Education University of Hong Kong. This work was supported by the Environment and Conservation Fund of the Hong Kong Special Administrative Region Government (No. 2020-76), SKLMP Seed Collaborative Research Fund (No. SCRF/0026), and the Dean's Research Fund (No. IRS-4 RG30/2021-2022R) of The Education University of Hong Kong.