Produção de hidrogênio via lactato obtido a partir da cofermentação de água residuária de fecularia de mandioca e glicerol

Abstract

The rising demand for sustainable energy sources is increasing interest in the biological production of hydrogen, which is a clean and efficient alternative to traditional energy sources. This study explored the possibility of producing bioH2 using a medium rich in lactic acid as a substrate, obtained from the co-fermentation of cassava starch factory wastewater (CSW) and glycerol. The process was divided into two stages: (i) producing lactic acid-rich fermentate (FLa) in an anaerobic sequential batch reactor (ASBR) from co-fermentation of CSW and glycerol (1.5% v/v), and (ii) converting FLa to bioH2 in a continuous multi-tube reactor (CMTR). The CMTR was tested with three increasing volumetric organic loads (VOL): 48, 72, and 96 g COD L⁻¹ d⁻¹. Results showed that the lactic fermentation stage produced a uniform substrate high in lactic acid (41%) and glycerin (52%). In the CMTR, the highest volumetric hydrogen production rates (VHP = 1,960.3 mL H₂ L⁻¹ d⁻¹) and biogas flow rates (BGF = 9,360.9 mL d⁻¹) occurred with the highest VOC applied. Conversely, the highest hydrogen yield (HY = 14.1 mmol H₂ g COD⁻¹) and the greatest conversion of lactic acid (95%) and glycerol (65%) occurred at intermediate COV levels. Soluble metabolite analysis suggested the predominance of the butyric pathway in the E2 test, associated with better stability and less formation of compounds like ethanol and propionic acid that divert carbon and decrease H₂ production. Although the acetic pathway is more efficient for hydrogen generation, the butyric pathway tends to be favored in real systems due to its greater operational stability. It is concluded that combining CSW co-fermentation with glycerol and prior lactic acid production, followed by application in CMTR for H2 generation, is a promising strategy for valorizing agro-industrial waste and sustainably producing bioH2.