Microwave-enhanced extraction of lignin from birch in formic acid: Structural characterization and antioxidant activity study

► Birch was subjected to a microwave assisted formic acid extraction process. ► 89.77% of the lignin was released under microwave heating for 30 min. ► The structure of the extracted lignin was characterized compared with MWL. ► Antioxidant activity of the extracted lignin was higher than that of MWL.