Chemo-Sonic Pretreatment Approach on Marine Macroalgae for Energy Efficient Biohydrogen Production

Abstract

The core objective of this analysis is to implement a combination of alkaline (NaOH) and sonication pretreatment techniques to produce energy-efficient biohydrogen from the marine macroalgae Chaetomorpha antennina. Anaerobic fermentation was implemented in control, sonic solubilization (SS) and sonic alkali solubilization (SAS) pretreatment for 15 days. In control, a biohydrogen production of 40 mL H2/gCOD was obtained. The sonicator intensities varied from 10% to 90% for a period of 1 h during SS pretreatment. About 2650 mg/L SCOD release with a COD solubilization of 21% was obtained at an optimum intensity of 50% in a 30 min duration, in which 119 mL H2/gCOD biohydrogen was produced in the anaerobic fermentation. SAS pretreatment was performed by varying the pH from 8 to 12 with the optimum conditions of SS where a SCOD release of 3400 mg/L, COD solubilization efficiency of 26% and a maximum biohydrogen production of 150 mL H2/gCOD was obtained at a high pH range of 11 in the fermentation. The specific energy required by SS (9000 kJ/kgTS) was comparatively higher than SAS (4500 kJ/kg TS). SAS reduced half of the energy consumption when compared to SS. Overall, SAS pretreatment was found to be energetically favorable in a field application.