Biohydrogen and methane production via a two-step process using an acid pretreated native microalgae consortium

- A native microalgae consortium was pretreated using thermal-acidic hydrolysis.
- Hydrogen and methane were produced sequentially with the acidic hydrolysates.
- The lower acid concentration gave the highest H2 and CH4 production.
- H2 and CH4 yields were up to 45.4 and 432 mL g VS−1, respectively.

A native microalgae consortium treated under thermal-acidic hydrolysis was used to produce hydrogen and methane in a two-step sequential process. Different acid concentrations were tested, generating hydrogen and methane yields of up to 45 mL H2 g VS−1 and 432 mL CH4 g VS−1, respectively. The hydrogen production step solubilized the particulate COD (chemical oxygen demand) up to 30%, creating considerable amounts of volatile fatty acids (up to 10 g COD L−1). It was observed that lower acid concentration presented higher hydrogen and methane production potential. The results revealed that thermal acid hydrolysis of a native microalgae consortium is a simple but effective strategy for producing hydrogen and methane in the sequential process. In addition to COD removal (50-70%), this method resulted in an energy recovery of up to 15.9 kJ per g of volatile solids of microalgae biomass, one of the highest reported.