| An efficient laboratory fermentor was developed which would adequately mix high-solids slurries. High-solids fermentations of feedlot manure and municipal solid waste with sewage sludge (MSW/SS) were performed to determine the feasibility of these two feedstocks for producing acetic acid and other volatile fatty acids. The highest acid concentrations and productivities were obtained with manure at 34.5 g total acid/L liquid (18.6 g acetic acid/L liquid) and 2.98 g total acid/(L liquid{dollar}cdot{dollar}d), respectively, for manure; 28.7 g total acid/L of liquid (18.0 g acetic acid/L liquid) and 2.28 g total acid/(L liquid{dollar}cdot{dollar}d), respectively, for MSW/SS). On the other hand, the maximum acid yields were higher for MSW/SS (0.34 g total acid/g VS fed for MSW/SS, 0.24 g total acid/g VS fed for manure).; The Continuum Particle Distribution Modelling (CPDM) method of Loescher was applied to the MSW/SS and manure fermentations. The model agreed with experimental reactor productivities (g acid produced/(L of liquid{dollar}cdot{dollar}d)) within 10% in all but one case. The model was used to predict final acid product concentrations and substrate conversions at a variety of liquid and substrate feed rates.; Iodoform was an effective inhibitor of methane production. In fermentations at 40{dollar}spcirc{dollar}C, it could completely inhibit methane production. It did however, shift the fermentation product spectrum away from acetic acid to long-chain volatile fatty acids. Thermophilic fermentations and acetogenic organisms were identified as potential means to shift the product spectrum to greater acetic acid production. |
