Fermentative conversion of sucrose and pineapple waste into hydrogen gas in phosphate-buffered culture seeded with municipal sewage sludge

Abstract

Sucrose and pineapple waste (PAW) were used as the carbon substrate to produce H 2 using municipal sewage sludge as the H 2 producer. The effects of pH, substrate concentration and type of buffer on H 2 production were studied. Regardless of the type of carbon substrate, phosphate-buffered medium exhibited much higher H 2 production efficiency and lower CO 2/H 2 ratio than those obtained in medium containing bicarbonate buffer. For H 2 production from sucrose-based medium, the best pH and carbon substrate (sucrose) concentration was 7.5 and 20 g COD/l, respectively, giving a maximum H 2 production rate ( v H 2 , max ) and H 2 yield ( Y H 2 ) of 745 ml/h/l and 2.46 mol H 2/mol sucrose (or 5.27 mol H 2/g COD), respectively. When using PAW as the substrate, the H 2 production performance was similar with or without additional nitrogen source, indicating that the PAW substrate contained sufficient nitrogen source for cell growth and H 2 production. The v H 2 , max and Y H 2 obtained from phosphate-buffered PAW medium (Medium B) was 383 ml/h/l and 5.92 mol H 2/g COD, respectively, which is 95 and 64% higher than the carbonate-buffered medium (Medium D). Although attaining lower H 2 production rate than sucrose medium, the PAW-based medium gave comparable H 2 yield, suggesting the feasibility of using the renewable resource (PAW waste) for fermentative H 2 production. Increasing the culture volume (using PAW medium) from 100 ml to 2.5 L (a 25-fold increase) caused a 20–40% decrease in the H 2 production rate and H 2 yield, probably due to poor mixing efficiency in the scale-up experiments.