Jeju Island is one of South Korea’s most famous tourist destinations, known not only for its breathtaking landscapes but also for its mandarin culture, a symbol of the island. It is precisely here that a rather interesting anaerobic digestion project was developed. The project involved the installation of a wastewater treatment plant deriving from the production of mandarin juice. This wastewater, after having undergone a pre-treatment process, flows into a digester for the production of biogas! Thanks to this approach, what was previously considered waste can be valued and used to produce clean energy. Collected during the International Biogas Convention 2020, promoted by the German Biogas Association