Fermentative production of hydrogen from cassava processing wastewater by Clostridium acetobutylicum

This work reports on the effect of initial substrate concentration on COD consumption, pH, and H 2 production during cassava processing wastewater fermentation by Clostridium acetobutylicum ATCC 824. Five initial COD wastewater concentrations, namely 5.0, 7.5, 10.7, 15.0, and 30.0 g/L, were used. The results showed that higher substrate concentrations (30.0 and 15.0 COD/L) led to lower H 2 yield as well as less efficient substrate conversion into H 2. On the other hand, initial COD concentrations of 10.7, 7.5 and 5 g/L furnished 1.34, 1.2 and 2.41 mol H 2/mol glucose, with efficiency of glucose conversion into H 2 of 34, 30, and 60% (mol/mol), respectively. These results demonstrate that cassava processing wastewater, a highly polluting effluent, can be successfully employed as substrate for H 2 production by C. acetobutylicum at lower COD concentrations. ► Five concentrations of cassava processing wastewater were used for H 2 production. ► Higher substrate concentrations (30.0 and 15.0 gCOD/L) led to lower H 2 yield. ► Lower cassava wastewater COD concentrations lead to higher H 2 production. ► 2.41 mol H 2/mol glucose was obtained using 5g COD/L of cassava wastewater. ► Cassava wastewater can be used to produce clean energy.