One waste and two products: choosing the best operational temperature and hydraulic retention time to recover hydrogen or 1,3-propanediol from glycerol fermentation

Abstract

This study aimed to compare the production of hydrogen and 1,3-propanediol from crude glycerol (10 g/L) in mesophilic (30 °C) and thermophilic (55 °C) anaerobic fluidized bed reactors, namely AFBR_{30 °C} and AFBR_{55 °C}, respectively, at hydraulic retention times (HRT) reduced from 8 to 1 h. In AFBR_{30 °C}, the absence or low hydrogen yields can be attributed to the production of 1,3-propanediol (maximum of 651 mmol/mol glycerol), and the formation of caproic acid (maximum of 1097 mg/L) at HRTs between 8 and 2 h. In AFBR_{55 °C}, the hydrogen yield of 1.20 mol H₂/mol glycerol consumed was observed at the HRT of 1 h. The maximum yield of 1,3-propanediol in AFBR_{55 °C} was equal to 804 mmol/mol glycerol at the HRT of 6 h and was concomitant with the production of hydrogen (0.87 mol H₂/mol glycerol consumed) and butyric acid (1447 mg/L).

Keywords: Anaerobic fluidized bed reactor; Dark fermentation; Glycerol; Mesophilic; Thermophilic.