This project focused on scaling up the laboratory fermentation of biomass to carboxylic acids. Four 1050-gallon tanks were used to simulate four-stage countercurrent fermentation. Most laboratory fermentations have been performed with 1-L fermentors. The purpose of the pilot plant was to show that the process is scalable. The inocula were marine and terrestrial microorganisms. Office paper was used as an energy source, and chicken manure provided the necessary nutrients. The substrate was 80 wt% office paper and 20 wt% chicken manure. Calcium carbonate was used as a neutralizing agent and iodoform served as a methane inhibitor. The fermentor temperature was 40 oC and the pH was 6.0. The highest total acid concentration obtained was 32.4 g/L, operating with a volatile solids loading rate (VSLR) of 1 g/(L liq ??d) and a liquid residence time (LRT) of 80 days. Typical laboratory VSLRs and LRTs are 3 to 10 g/(L liq ??d) and 10 to 30 days, respectively. Similar VSLRs and LRTs were not achieved at the pilot scale because the design was limited by the ability to effectively separate large amounts of solids and liquids. The bulk of the effort was concentrated on overcoming temperature control and solids-handling issues. Design modifications included a redesigned temperature control system and a new material transfer method.
