Characterization and CPDM modeling of volatile fatty acid fermentation with cotton gin trash and chicken manrure as substrates

Abstract

With literally tons of biomass produced annually, a process that uses this waste as a feedstock would help reduce the problem of disposal. The MixAlco process is one that does just that. It converts biomass through anaerobic fermentation into volatile fatty acids, mixed alcohols, and ketones. These products can be used as raw chemicals or as fuel for their heating value. The process must be implemented on an industrial scale in order to obtain significant amounts of the products. The substrates evaluated in this study are municipal solid waste (MSW), sewage sludge (SS), cotton gin trash (GT), and chicken manure (CM). The product concentrations obtained from using MSW and SS as the substrate were low compared to those obtained with GT and CM. Maximum product concentrations when using GT and CM at a temperature of 55°C were 22 g of total acid/L with acetic acid constituting 78 % of the total acids. The Continuum Particle Distribution Modeling (CPDM) method is also applied to data collected for batch reactions. The model can accurately predict acid concentrations when excessive decomposition of the acid is not occurring. However, when liquid residence times are extended and the products decompose, the model does not accurately predict the decreasing product concentrations.