The disposal of biomass waste containing large amounts of water by burial in the ground or burning causes environmental problems. Therefore, efficient methods for the treatment of biomass waste are required. In this study, conversion of livestock manure, a significant biomass waste, to useful chemicals such as ketones was carried out using a new conversion process consisting of hydrothermal treatment and reaction in the presence of an iron oxide. We succeeded in the selective production of acetone from a livestock manure-derived slurry liquid using the iron oxide catalyst. Moreover, the acetone yield in the product liquid was increased with increasing concentration of acetic acid in the slurry liquid. (C) 2010 Elsevier B. V. All rights reserved.