Recycling of waste coffee pods

Abstract

Plastic waste management has become a key environmental dilemma worldwide because of the significant increase in the consumption of plastic and its short lifespan. Besides general plastic waste, recently, the production of waste plastic coffee pods is drastically increasing. Traditional plastic waste disposal methods, such as the use of landfills and incinerators, are not environmentally friendly. Thus, alternative ways of plastic waste management are under active investigation. One such option is to use the pyrolysis in-line reforming process to transform plastic waste into hydrogen, which is a form of clean energy. Pyrolysis is a thermal decomposition process of organic materials at high temperatures in the absence of oxygen, but the conventional process is expensive because of inefficient heating and associated heat losses. Therefore, in this study, the use of microwave to overcome this issue is explored. This project investigated the use of (a) a microwave for the pyrolysis of polypropylene (PP), high-density polypropylene (HDPE) and waste coffee pods (which mainly consist of polypropylene); (b) two reactors for the pyrolysis of coffee pods: batch and fixed-bed reactor; and (c) a nickelbased catalyst in the catalytic process for the waste coffee pods. The results from the microwave pyrolysis showed that the highest gas yield of 45% by weight was obtained at 500 °C for high-density polyethylene and 41% and 58% for waste coffee pods and polypropylene at 700 °C, respectively. Thus, the highest gaseous yield was from polypropylene pyrolysis, which indicated that it could undergo degradation. The waste coffee pods were the only plastic to form carbon dioxide and monoxide owing to oxygen present in its structure. Further, the results from the microwave in-line catalytic reforming of waste coffee pods demonstrated the enhancement of hydrogen content with nickel loading in the activated carbon catalyst. The highest volume of hydrogen produced was 76% of total gases at 900 °C with 5% nickel loading in the activated carbon catalyst. These findings highlight microwave in-line catalytic reforming viii as a promising method for efficient plastic waste management, particularly for producing clean energy from waste coffee pods.

Date of Award	2023
Original language	English
Awarding Institution	Western Sydney University
Supervisor	Dharma Hagare (Supervisor), Sathaa Arumugam Sathasivan (Supervisor), Arash Tahmasebi (Supervisor) & Meenakshi Arora (Supervisor)