Oil removal from waste coffee grounds using two-phase solvent extraction enhanced with ultrasonication

The objective of this study was to investigate the kinetics of ultrasound assisted-two phase oil extraction from waste coffee grounds with high moisture content. Waste coffee grounds is the wet residue which contains approximately 13% (db) oil. Ultrasound-assisted two-phase oil extraction method successfully extracted 98% of the available oil from the waste coffee grounds in 30 min. Ultrasonication reduced the amount of hexane used for the extraction. Fatty acid methyl ester compositions of the waste coffee oil and the soybean oil were similar. The kinetics of oil extraction from waste coffee grounds were modeled using a two-exponential mathematical equation. Establishing oil extraction facilities at locations where the ready-to-drink coffee products are produced and using two-phase oil extraction eliminate major challenges of collection, transportation and drying, which makes waste coffee grounds a viable feedstock for biodiesel production.