UTILIZATION OF ROBUSTA COFFEE GROUNDS AS BIODIESEL AND BIOCHAR THROUGH EXTRACTION WITH MTBE SOLVENT

• Main Author: Zulia Rahma, Qori
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/68812
• Institution: Institut Teknologi Bandung

Robusta coffee grounds are one of the food waste from local coffee shops, which generally end up in landfills. Robusta coffee grounds can be used for many purposes, one of wich is to be processed as biodiesel. Secondary dregs from coffee oil extraction for biodiesel raw material were used as biochar. Biochar has recently proved to be effective in various applications, including reconditioning of agricultural soils. Utilization of an organic solvent, namely MTBE (Methyl tert-Butyl Ether) to extract oil from robusta coffee grounds was carried out by considering the feasibility of the physicochemical characteristics of biodiesel. Soxhletation method was employed to dissolve robusta coffee grounds oil in MTBE. In this study, robusta coffee grounds had an average fat content of 7.54%. In the early stages, robusta coffee grounds must be dry because the water content causes an impurity in biodiesel. Based on data from GC-MS (Gas Cromatography and Mass Spectroscopy), robusta coffee crude oil contains 8.17% oleic fatty acid (C18H34O2), which is ideal for biodiesel production since it has one double bond. Fatty acid ester biodiesel was obtained from the alcoholysis process. In this study, a transesterification process was carried out using methanol (CH3OH) alcohol, which has a more acidic nature combined with a sulfuric acid catalyst (H2SO4) to attract FFA (Free Fatty Acid) content, which affects its physicochemical properties. This was conducted twice with excess methanol concentration. The FFA content of more than 1% in the ester was followed by a transesterification process using ethanol (C5H2OH) with a NaOH catalyst as a base. The oxidation stability of biodiesel from the process that has been carried out showed outstanding results and was stable for 10.37 hours in the rancimat test due to the dissociation of volatile carboxylic acids which last longer in the oxidation process than water in the measurement cell. The mixing is also carried out to produce B30 fuel. Based on the parameters of SNI (Indonesian National Standard) 7182:2018, robusta coffee biodiesel meets the limits of density, viscosity, acid number, saponification number, and iodine number with a high calorific value. Besides, secondary pulp processing from oil extraction was made into biochar through pyrolysis reactors and muffle furnaces. This was conducted so that all materials from ro busta coffee grounds can be utilized optimally. Meanwhile, biochar can be utilized in agriculture to maintain soil fertility. Biochar, as a carbon-rich product which has gone through a thermal stabilization process with either a pyrolysis reactor (PYRO) or a muffle furnace (MF), shows a carbon content exceeding 60% at a temperature variation of 300- 600? following the class 1 biochar IBI recommendation (International Biochar Initiative). These results were confirmed by the EDS (Electron Dispersive Spectrometry) test, where the carbon content of biochar at a temperature of 600 for PYRO and MF was 85.26% and 92.83%, respectively. In addition, the extractive chemical components of biochar were discerned using NMR (Nucleus Magnetic Resonance). Biodiesel from robusta coffee grounds can be used as diesel fuel because it meets SNI and can be used as a B30 mixture. Meanwhile, biochar from robusta coffee secondary dregs has a carbon content percentage of more than 60% according to the IBI criteria. Meanwhile, the results of the NMR test did not show the peak of toxic foreign chemical content, so biochar is safe to be applied in agriculture.