Serious environmental concerns regarding the use of fossil-based fuels have raised awareness about necessity of alternative clean fuels. Biodiesel fuel is considered a clean, biodegradable and non-toxic alternative for diesel fuel. Given the large global production and consumption of coffee, coffee waste is a potential non-edible feedstock for biodiesel production due to its high oil content and availability worldwide. In this paper, direct, so-called in situ transesterification by which biodiesel is produced from coffee grounds without the need for prior oil extraction and esterification processes was investigated. In situ transesterification was performed using methanol and an alkaline conventional homogeneous and unconventional heterogeneous catalyst in a magnetic stirrer and Soxhlet apparatus. Furthermore, this paper provides insight into the comparison of unconventional and conventional transesterification reactions. When carrying out the conventional method, the oil was extracted by the Soxhlet method using n-hexane and then purified with a potassium carbonate-based deep eutectic solvent. The synthesis was carried out with potassium hydroxide as a catalyst and the obtained crude biodiesel was purified with a choline chloride based deep eutectic solvent.