Ammonia Fiber Explosion Research Articles

Volatile fatty acid fermentation of AFEX-treated bagasse and newspaper by rumen microorganisms

The anaerobic digestion of bagasse and newspaper by rumen microorganisms was studied. A one-half replicate of a 2 5 factorial design was used to evaluate the effect of type of substrate (bagasse and newspaper), AFEX (Ammonia Fiber Explosion) pretreatment, liquid residence time (LRT), solid/liquid residence time ratio (SRT/LRT), and loading rate (LR) on volatile fatty acid (VFA) yield, productivity, and acid composition. A fermentor for the continuous culture of rumen microorganisms, which allows solids to be retained longer than liquid (SRT/LRT> 1), was used. Yields averaged 8.8 mmoles and 5.8 mmoles VFA per g volatile solids (VS) in bagasse and newspaper fermentations, respectively. The propionic acid molar percent was 52% higher in bagasse fermentation (19%) than in newspaper fermentation (12.5%). AFEX pretreatment increased VFA yield by 21% and decreased propionic acid molar percent by 9.1 %. The best reactor performance (i.e., high VFA yield and high VFA productivity) was achieved with AFEX-treated material at a LR of 14.1 g substrate per 1 day, LRT of 11 h, and SRT of 44 h. At these experimental conditions, productivity and yield were 163 mmoles VFA per 1 per day and 0.64 g VFA/g VS in bagasse fermentation, and 81 mmoles per 1 per day and 0.31 g VFA/g VS in newspaper fermentation. The rumen fermentation product yields are significantly higher than the sugar yields from extracellular cellulase/hemicellulase. A promising application of the rumen fermentation is to produce mixed VFA calcium salts which may be used to remove sulfur from coal-fired boilers. It is estimated that these salts may be produced from municipal solid waste for $119–137/tonne.

Pretreatment of lignocellulosic municipal solid waste by ammonia fiber explosion (AFEX)

The Ammonia Fiber Explosion (AFEX) process treats lignocellulose with high-pressure liquid ammonia and then explosively releases the pressure. The combined chemical effect (cellulose decrystallization) and physical effect (increased accessible surface area) dramatically increase lignocellulose susceptibility to enzymatic attack. For example, bagasse digestibility is increased 5.5 times and that of kenaf core is increased 11 times using extracellular cellulases fromTrichoderma reesei. In this study, we applied the AFEX process to mixed municipal solid waste (MSW) and individual components (e.g., softwood newspaper, kenaf newspaper, copy paper, paper towels, cereal boxes, paper bags, corrugated boxes, magazines, and waxed paper). Softwood newspaper proved to be the most difficult component to digest because of its high lignin content. A combination of oxidative lignin cleavage and AFEX was required to increase softwood newspaper digestibility substantially, whereas AFEX alone was able to make kenaf newspaper digestible. Because most MSW components have been substantially delignified in the paper-making process, AFEX only marginally increased their digestibility.