Simultaneous production of nutritional compounds and hydrochar from Chlorella pyrenoidosa via hydrothermal process

Abstract

Hydrothermal process is an eco-friendly method for simultaneously extracting antioxidant compounds and producing hydrochar. This study examined the simultaneous production of nutritional compounds and hydrochar from Chlorella pyrenoidosa via a hydrothermal process. The experiments were conducted using a batch reactor at varying temperatures (160, 180, and 200 °C) and holding times (10, 20, and 30 min). The results revealed that phenolic contents, antioxidant activity, and hydrochar production were strongly affected by both temperature and time. The highest total phenolic content (1.70 ± 0.16 mg/g) and antioxidant activity (94.2 ± 1.8 %) were found in process water at 200 °C with a holding time of 20 min. Under these conditions, a hydrochar yield of 30.79 % was obtained. Intriguingly, the hydrochar obtained at 200 °C exhibited higher heating values (24.93–28.32 MJ kg−1) than typical sub-bituminous coals, giving it potential for use as a solid fuel.