Charcoal briquette production from waste in the coffee production process using hydrothermal and torrefaction techniques: A comparative study with carbonization technique

Abstract

This research aimed to study charcoal briquette production from coffee production waste, i.e., coffee parchment (CP) and coffee cherry pulp (CCP). The carbonization technique (CT) was studied in five mixtures (CP and CCP ≈ 0–90%) and three pressures (1000–1600 psi) to determine the appropriate conditions. The torrefaction technique (TT) and hydrothermal technique (HT) were subsequently performed under proper conditions from the CT to investigate further the fit temperatures (200–260 °C) and reaction times (40–120 min). The fuel characteristics were examined regarding the calorific value (CV), proximate and ultimate analyses, mechanical properties, and utilization properties. The results demonstrated the notable influence of interaction between the mixture and pressure factors and individual mixture on the fuel properties, whereas personal pressure have an insignificant effect. The ratio of CP ≈ 90% and binder ≈10% at a pressure of 1600 psi in the CT prepared appropriate fuel properties (calorific value ≈ 27 MJ/kg, fixed carbon content ≈ 65%). Interestingly, almost all conditions of the TT and HT provided greenhouse gas emissions lower than the CT. The TT and HT at 260 °C for 120 min provided high calorific values (25–26 MJ/kg) with other fuel characteristics in the acceptable standard, except for the fixed carbon content.