Tuesday, May 3, 2011
In Japan, the amount of the food waste is over 22 Mt/y and over 70% of the food waste is burned or landfilled. About 24% of the food waste is converted to fertilizer or feed to livestock. However, conversion of the food waste to fertilizer or feed is not considered to be an appropriate recycling method because the food waste is heterogeneous and perishable. The high content of water in the food waste also becomes trouble on the recycling. In this study, upon hydrothermal treatment of boiled rice as a model constituent in the food waste, additive effects of acetic acid and effects of holding time are discussed. After hydrothermal treatment of boiled rice at 200°C for 0 min., 94% of boiled rice became the water soluble constituent, however, the glucose yield was negligible. On the other hand, the glucose yield increased significantly by addition of 0.26-0.65 mol/L of acetic acid upon the treatment of boiled rice. Particularly, the maximum glucose yield (56%) was obtained by addition of 0.52 mol/L of acetic acid upon the treatment of boiled rice. However, the glucose yield decreased and the yield of the other constituents increased with the increases of holding time to 30 min upon hydrothermal treatment of boiled rice at 200°C with 0.52 mol/L of acetic acid. It was considered that hydrolysis of boiled rice to yield glucose was enhanced due to the increase of the amount of H+ derived from acetic acid during hydrothermal treatment with 0.52 mol/L of acetic acid.