The Biological Hydrogen Production Potential of Agroindustrial Residues

The use of agroindustrial residues for bioenergy production can be an attractive alternative from both the environmental and economic perspective. Cassava wastewater (CWW) and cheese whey (CW) are potential substrates for biological hydrogen production (HP) since they are rich in carbohydrates. The biological HP by using a photoheterotrophic bacterial consortium can be advantageous compared to pure culture. In this study, six concentrations of hydrolysed CWW (varying from 5 to 36 g COD L-1) and CW powder (4.7-31.1 g COD L-1) were used for HP by microbial consortium under anaerobic conditions and constant illumination. The experiments were performed in batch reactors under controlled pH (6.5-7.0) in non-sterile conditions. Using CWW, the highest HP was 36.1 mmol H-2 L-1 culture in the concentration of 21.3 g COD L-1. Using CW, the highest HP was 28.5 mmol H-2 L-1 culture in the concentration of 31.1 g COD L-1. The hydrogen yields (HY) were higher at lower substrate concentrations: 1.1 mmol H-2 mmol(-1) glucose for CWW and 2.0 mmol H-2 mmol(-1) lactose for CW. Carbohydrate removal was high for both substrates (>90.2 %), but COD removal did not reach such high values (<42.4 %). Higher CWW concentrations inhibited HP; however, a different trend was observed when increasing the CW concentration. Toxic compounds present in CWW could be responsible for the inhibition of HP.