Effect of C/N and Substrate Concentration on Fermentative Hydrogen Production from Food Waste

Abstract

Fermentative hydrogen production from artificial food waste by batch cultivation under a pH of 6.0 and a temperature of 37°C was studied by using mesophilic bacterium HN001. The aim of this study is to investigate the effect of the ratio between carbon and nitrogen concentration (C/N) and substrate concentration on hydrogen fermentation. C/N was changed from 9 to 23 by adding entrails of fish to the artificial food waste because entrails contain lots of Nitrogen. Hydrogen production rate and hydrogen yield increased from 0.3L L-culture^-1 h^-1 to 1.2L L-culture^-1 h^-1 and from 22L kg-wet^-1 to 67L kg-wet^-1 respectively when C/N decreased from 23 to 20. Volatile fatty acid also changed, acetate and butyrate increased and lactate decreased, by decreasing C/N. Hydrogen yield was relatively low though hydrogen production rate did not decreased when yeast extract and casamino acids were used as nutrients instead of entrails. However, it was improved by adding yeast extract, casamino acids and iron. This result indicates that entrails could be utilized as not only nitrogen source but also mineral source for hydrogen fermentation. Hydrogen productivity was also affected by substrate concentration. Hydrogen production rate increased along with the increase of substrate concentration form 100 g-wet L^-1 to 300 g-wet L^-1. On the other hand, hydrogen yield on 500 g-wet L^-1 decreased compared with them between 100 g-wet L^-1 and 300 g-wet L^-1.