Batch biohydrogen production from dilute acid hydrolyzates of fruits-and-vegetables wastes and corn stover as co-substrates

Fruits-and-vegetables wastes (FVW) and corn stover (CS) are two of the most recurred lignocellulosic biomasses used for biofuel production. In this work, the co-processing of FVW and CS for biohydrogen production was proposed and evaluated through a set of experimental designs. First, a 5 × 2 general factorial was applied on the dilute acid pretreatment at five levels of FVW:CS ratios (0:1, 1:3, 1:1, 3:1 and 1:0 dry mass basis) and two levels of the type of catalyst (HCl or H₂SO₄ at 0.5% in volumetric basis). Then, biohydrogen production using the dilute acid hydrolyzates was carried out in batch mode at 35 °C in a 3² factorial design, the factors being the inoculum to substrate ratio (0.8, 1.0, and 1.2 g g⁻¹) and the initial concentration of reducing sugars (10, 13 and 16 g L⁻¹). The effects of the type of acid catalyst and the FVW:CS ratio were significant in terms of sugars production and yield. The best catalyst was HCl for the 3:1 FVW:CS ratio, which produced monomeric sugars concentrations of 10.0, 3.7 and 2.9 g L⁻¹ for glucose, xylose and arabinose, respectively. The hydrolyzates were suitable for biohydrogen production, reaching yields of 2.31 mol H₂ mol⁻¹glucose and hydrogen production rates of 8.83 mL H₂ h⁻¹. An economic prospection at lab scale demonstrated that hydrogen production presented net revenues of 0.009 USD per kg of co-substrates, resulting in 24% profitability of hydrogen production over its production costs. Therefore, this co-processing is an interesting proposal with further applications on biorefinery models.