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

Sucrose and pineapple waste (PAW) were used as the carbon substrate to produce H2 using municipal sewage sludge as the H2 producer. The effects of pH, substrate concentration and type of buffer on H2 production were studied. Regardless of the type of carbon substrate, phosphate-buffered medium exhibited much higher H2 production efficiency and lower CO2/H2 ratio than those obtained in medium containing bicarbonate buffer. For H2 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 H2 production rate (vH2,max)(vH2,max) and H2 yield (YH2)(YH2) of 745 ml/h/l and 2.46 mol H2/mol sucrose (or 5.27 mol H2/g COD), respectively. When using PAW as the substrate, the H2 production performance was similar with or without additional nitrogen source, indicating that the PAW substrate contained sufficient nitrogen source for cell growth and H2 production. The vH2,maxvH2,max and YH2YH2 obtained from phosphate-buffered PAW medium (Medium B) was 383 ml/h/l and 5.92 mol H2/g COD, respectively, which is 95 and 64% higher than the carbonate-buffered medium (Medium D). Although attaining lower H2 production rate than sucrose medium, the PAW-based medium gave comparable H2 yield, suggesting the feasibility of using the renewable resource (PAW waste) for fermentative H2 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 H2 production rate and H2 yield, probably due to poor mixing efficiency in the scale-up experiments.