Co-circularity of spent coffee grounds and polyethylene via co-pyrolysis: Characteristics, kinetics, and products. (1st April 2023)

• Record Type: Journal Article
• Authors: Fu, Jiawei; Wu, Xijian; Liu, Jingyong; Evrendilek, Fatih; Chen, Tao; Xie, Wuming; Xu, Weijie; He, Yao
• Is Part Of: Fuel. Volume 337(2023)
• Publication Date: 2023-04-01
• Subjects: Coffee grounds -- Polyethylene -- Co-pyrolysis -- Py-GC/MS -- Dynamic optimization; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2022.127061
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: Co-pyrolysis of coffee grounds (CG) and polyethylene (PE) was characterized. Its blend ratio, heating rate and temperature dependencies were quantified. Co-pyrolysis of 70% CG and 30% PE had the lowest activation energy and emissions. The co-pyrolysis yielded hydrocarbons and alcohols up to 93.61%. The best co-pyrolysis conditions were 70% CG and 30% PE and 517–1000 ℃. Abstract: Spent coffee grounds (CG) and polyethylene (PE) are the two typical types of major solid wastes. Their co-pyrolysis may be leveraged to reduce their waste streams and pollution and valorize energy and by-products. In this study, their co-pyrolysis performances, interaction effects, kinetics, and products were characterized in response to the varying temperature and blend ratio. The co-pyrolysis exhibited the two main stages of (1) the degradation of CG (180–380 °C) and (2) the depolymerization of PE and the decomposition of lignin (380–550 °C). The pyrolysis performance rose from 1.34×10 −4 % 3 ·min −2 ·°C −3 with the mono-pyrolysis of CG to 26.32×10 −4 % 3 ·min −2 ·°C −3 with the co-pyrolysis of 10 % CG and 90 % PE. The co-pyrolysis of 70 % CG and 30 % PE (CP73) achieved a lower activation energy than did the mono-pyrolysis of the two fuels. The products of the CG pyrolysis included a large number of alcohols, ethers, ketones, esters, and other oxygen-containing compounds, with a proportion as high as 65.01 %. The products of CP73 at 550 °C resulted in the yields of hydrocarbons and alcohols up to 93.61 %, beneficial to the further utilization of the co-pyrolytic products. Not only did the co-pyrolysis valorize its products, but also it enhanced their co-circularity. Artificial neural network-based joint optimization showed CP73 in the range of 517–1000 °C as the best combination of the conditions. The study provides new insights into the co-pyrolytic disposal of spent coffee grounds and polyethylene so as to improve the waste stream reduction and the valorization of energy and products.