Agricultural HDPE pyrolysis for environmental management: Feedstock complexity, reaction dynamics, and circular...

The majority of the high-density polyethylene (HDPE) agricultural waste is produced in agricultural practices and typically ends up contaminated. This review will present current research into the pyrolysis of agricultural HDPE and will focus on how operating conditions and the presence of contaminants influence the behavior of the pyrolysis process and the products formed during the process. While available data indicates that contaminants may alter heat transfer rates and chemical reaction pathways, the formation of unwanted emissions is also generally influenced by contaminant levels. Differences in heating rate, vapor residence time and reactor design explain many of the variations found in oil, gas and char yield values in previous reports. The kinetic parameters obtained from thermogravimetric analysis have also proven difficult to use directly in pilot-scale reactors. Rather than comparing individual results from the literature, this review will identify common patterns and limitations in the research findings to date and highlight key knowledge gaps concerning feedstock preparation, emission reduction and process consistency. These knowledge gaps represent important steps toward translating laboratory-based studies of agricultural HDPE pyrolysis into environmentally acceptable practices.