Biofiltration of volatile ethanol using sugar cane bagasse inoculated with Candida utilis

Candida utilis (C. utilis) growing on sugar cane bagasse complemented with a mineral salt solution was studied for gaseous ethanol removal in a biofilter. Ethanol loads from 93.7 to 511.9 g/h m(3) were used, by varying both inlet ethanol concentration (9.72 to 52.4 g/m(3)) and air flow rate (1.59 x 10(-3) to 2.86 x 10(-3) m(3)/h). At a loading rate of 93.7 g/h m(3), a steady-state was maintained for 300 h. Ethanol removal was complete, and 76.3% of the carbon consumed was found in carbon dioxide. At an higher aeration rate (ethanol load=153.8 g/h m(3)), the biofilter displayed an average removal efficiency (RE) of 70%, and an elimination capacity (EC) of 107.7 g/h m(3). Only 64.4% of the carbon consumed was used for CO(2) production. Acetaldehyde and ethyl acetate in the outlet gas attained 7.86 and 20.4% in terms of carbon balance, respectively. In both cases, the transient phase was less than one day. At a high inlet ethanol concentration (52.4 g/m(3)), no steady-state was observed and the process stopped during the third day. In the three cases, final biomass was poor, ranging from 10.5 to 14.8 mg/g dm. Final pH 4.0-4.6, indicated that acidifying non-volatile metabolites, such as acetate, accumulated in the reactor.