An integrated green process: Subcritical water, enzymatic hydrolysis, and fermentation, for biohydrogen production from coconut husk

- Production of H2 from coconut husk was performed using 3 subsequent green processes.
- Severity factor strongly affected the sugar yield from SCW.
- The maximum sugar yield of 20.64% was obtained at mild severity factor.
- The degradation of lignocellulosic components confirmed the sugar obtained.
- Types of pressurizing gas determine the severity factor tendency for sugar yield.

The objective of this work is to develop an integrated green process of subcritical water (SCW), enzymatic hydrolysis and fermentation of coconut husk (CCH) to biohydrogen. The maximum sugar yield was obtained at mild severity factor. This was confirmed by the degradation of hemicellulose, cellulose and lignin. The tendency of the changing of sugar yield as a result of increasing severity factor was opposite to the tendency of pH change. It was found that CO2 gave a different tendency of severity factor compared to N2 as the pressurizing gas. The result of SEM analysis confirmed the structural changes during SCW pretreatment. This study integrated three steps all of which are green processes which ensured an environmentally friendly process to produce a clean biohydrogen.

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