Exploring the environmental suitability of plastic pyrochar as a potential landfill liner material

Plastic pyrochar possessing a porous structure with excellent adsorption, water retention and binding capacity makes it a potential material for landfill liner. Studies related to exploring its use and environmental impacts in any engineering application are very few. This paper analyses its suitability as a liner material by determining engineering properties and environmental implications. The plastic pyrochar used in this study was the char obtained during the pyrolysis process of plastic wastes such as cross-linked polyethene (XLPE) and polypropylene (PP). It was characterised by spectroscopic and microscopic analyses. The environmental assessments done by conducting leaching tests using distilled water, hexane and methanol-water mixture showed no significant quantity of toxic metals or compounds eluting from it. Geotechnical properties, viz. Atterberg limits, fine contents and hydraulic conductivity of plastic pyrochar were determined. Liquid limit and plasticity index values of 50% and 15% respectively, met the United States Environmental Protection Agency (USEPA) standards. It was found that plastic pyrochar is conducive as a liner material except for hydraulic conductivity. Mixing with finer soils like bentonite brought the hydraulic conductivity value within the stipulated range. Furthermore, it was shown that the process of washing of pyrochar caused the reduction of total dissolved solids, conductivity, salinity, and chloride content considerably. Therefore, it is advisable to wash the plastic pyrochar before its use in any engineering applications. Utilization of plastic pyrochar as a liner material with bentonite is an effective and sustainable approach for plastic waste management.