Understanding the Thermal and Physical Properties of Biochar Derived from Pre-washed Arabica Coffee Agroindustry Residues

Abstract

The excessive availability of coffee-cherry processing residues has garnered attention, owing to potential environmental concerns associated with ground disposal. The current investigation aims to disclose the characteristics of two main coffee agroindustry residues, i.e., coffee pulp and parchment, as well as the resulting biochar which is produced without chemicals and low energy involved. The effects of washing raw biomass on biochar’s physical–chemical properties were investigated. The pre-washed samples were prepared through the following steps: washing, soaking for 20 h, draining, rinsing, and drying under sunlight for 3 days. A slow pyrolysis process was performed at 420 °C in a pilot-scale apparatus to produce biochar. The results show that the pre-washing of feedstock reduced the ash content in coffee pulp biochar from 28.23 to 11.93%. The ash content of coffee parchment biochar decreased from 9.68 to 5.66% as a result of the washing treatment of the raw material. Furthermore, coffee pulp biochar experienced a 25.8% reduction in surface area, while 14% of the coffee parchment was lost due to washing treatment of raw feedstocks. The findings presented in this study offer new insights that are crucial for evaluating the feasibility and advancing the development of a large-scale commercial process for managing coffee agro-industry residues.

Graphical Abstract