Natural inducement of hydrogen from food waste by temperature control

An easy and simple method of producing H2 from food waste was devised. Although there was no inoculum addition or pretreatment, food waste was naturally decomposed and converted to H2 when cultivated at 50–60 °C in anaerobic state. Both the highest H2 yield of 1.79 mol H2/mol hexoseadded and a production rate of 369.1 ml H2/L/h were observed at 50 °C. While butyrate was the main by-product of the food waste cultivated at 50 °C, lactate whose producing-reaction is non-hydrogenic was dominant at 35 °C where the worst performance was observed. The degradation efficiency of volatile solids and carbohydrate was similar to 50% and 90%, respectively, at both temperatures. Polymerase chain reaction-denaturing gradient gel electrophoresis analysis clearly revealed that the role of temperature control was the microbial selection. At high temperature, the activity of indigenous lactic acid bacteria was suppressed while H2-producing bacteria, such as Clostridium sp., Acetanaerobacterium elongatum, and Caloramater indicus, were predominantly cultivated.