Characteristics of Char From Co-Pyrolysis of Biomass and Plastic Waste

Abstract

Development of alternative, clean and renewable energy production from different hydrocarbon materials helps to partially replace the limited resources of fossil fuels and also help reduce carbon emissions from fossil fuels that drives global warming. Biomass and bio-wastes are renewable and sustainable hydrocarbon resources, which can be used for energy and fuels production along with permanent disposal of plastic wastes. Landfills of wastes is unsustainable with additional problems of non-degradability and growing burden to the environment and society. Co-pyrolysis and co-gasification of biomass with different types of plastic wastes has shown to provide enhanced product yields and quality for syngas and liquid fuel production. To date, limited information is available on the understanding of chars produced from co-pyrolysis. The effect of co-pyrolysis on the type, quality and yield of chars produced is essential for efficient utilization of a wide variety of biomass, bio-waste and plastic waste resources. This paper provides information on the effect of plastic addition to the pyrolysis of biomass as well as the quality and quantity of char produced with different amounts of plastic waste added at different pyrolysis temperatures. TGA reactor was used for all these investigations and the quality of char produced was examined from the perspective of char combustion for energy production. Char is commonly produced as a by-product from pyrolysis and gasification reactors. Carbonization temperatures investigated were in the range of 573–773 K for 30 min using pinewood biomass, while recycled polyethylene terephthalate was used as plastic waste. The investigations revealed that chars produced from co-pyrolysis especially for carbonization temperature (Tc) of 673 K and above behaved completely differently than the chars produced from separate pyrolysis of biomass and plastic waste under the same pyrolysis conditions. These chars produced from co-pyrolysis were more uniform in their behavior in oxidation environment, with higher heat flow for almost similar quantities of chars during oxidation. This was conjectured to be from enhanced quality of chars produced having increased C content (from increased heavy aromatics and efficient loss of volatiles) during co-pyrolysis without any loss of char yield. The char yield was found to be equal or higher during co-pyrolysis compared to the weighted aggregate of individual pyrolysis. These investigations provided novel results on the behavior and capabilities of chars produced from co-pyrolysis of biomass and plastic wastes to provide a new avenue for the quality enhancement of bio-chars and efficient utilization of carbonaceous solid waste resources.