Eri Fumoto

Recovery of Ammonia and Ketones from Biomass Wastes

Huge amounts of biomass wastes, such as animal waste and sewage sludge, are produced continuously in farms and disposal plants. The most common method for treating these wastes is to use landfill and/or incineration methods that consume large amounts of energy and cause environmental problems such as air and soil pollution. Because biomass wastes contain nitrogen compounds and various hydrocarbons, a new alternative process to convert the wastes into useful chemicals is desirable. Ammonia, one such chemical, has been used as a fertilizer, and increasing interest has focused on it as a hydrogen carrier. Ammonia is a liquid around 0.8 MPa at room temperature and offers significant hydrogen storage capacity (17.7 wt% hydrogen in ammonia). Hydrogen has been produced by the decomposition of ammonia with catalysts, such as ruthenium and nickel (Ganley et al., 2004; Liu et al., 2008; Wang et al., 2004; Yin et al., 2004, 2006; Zhen et al., 2008). Hence, the recovery of ammonia from biomass wastes is demanded. After the treatment for ammonia recovery, the remaining liquid wastes containing lower ammonia concentrations could be used as liquid fertilizer, whereas the high concentration of ammonia in raw biomass wastes causes eutrophication of the soil. Biomass wastes also contain various hydrocarbons, and several methods exist, such as thermal cracking and fermentation, to convert these wastes into useful chemicals. Methane and hydrogen have been produced by the gasification of biomass wastes above 1000 K with the addition of steam or air (Gross et al., 2008; Nipattummakul et al., 2010). Supercritical water gasification is a method conducted under high pressure to produce hydrogen (Guo et al., 2010a). Fuel oil has been produced by the treatment of biomass wastes at relatively low temperatures of between 673 and 823 K (Shen et al., 2005). Anaerobic fermentation has produced methane (Guo et al., 2010b). The treatment of biomass wastes under moderate conditions is desirable because of the high moisture content of the wastes. Biomass wastes contain various oxygen-containing hydrocarbons, and thus the conversion of these hydrocarbons into useful chemicals, such as ketones, appears to be a promising approach. Acetone is used as a raw material for plastics, such as poly(methyl methacrylate) (PMMA) and polycarbonate (PC).