Fundamental Study of Gasification of Food Wastes Using Supercritical Water

Abstract

Food waste as biomass resources is discharged by about 20 million ton per year in Japan. To reduce and recycle food waste is social demand today. However, the food waste that is not recycled is as much as 16 million ton, only a small part of food wastes being recycled. The main reason for this low recycle rate is its high moisture content. Drying the food waste requires more energy than the waste itself possesses, which makes energy use of food waste difficult. To circumvent this problem, supercritical water can be applied. In supercritical water, the organic compounds are gasified easily into hydrogen and methane. For this process, drying is not necessary since the reaction takes place in water. In this study, we developed continuous-flow equipment for gasifying food waste in supercritical water with nickel catalyst, which is known to promote water-gas shift reaction. First, we gasified glucose to determine the reactor characteristics of the equipment. Then based on this result, we successfully gasified model food waste of 1 wt%-dry matter at 723 K, 25 MPa. It was found that application of enzyme is effective for smooth feeding of food waste.