“…However, to make the process economically viable, the selectivity must be increased, the pretreatment time reduced, and the chemicals recycled [ 41 , 45 ]. Furthermore, by separate usage or combining the alkaline treatment with physical techniques, such as microwave [ 46 , 47 , 48 , 49 ], ultrasound irradiation [ 18 , 19 , 41 , 49 , 50 , 51 ], or freeze–thaw (FT) cycles [ 44 , 47 , 52 ], the alkaline extraction can be improved even further taking into account the final objectives.…”