2-15: Effects of low-moisture anhydrous ammonia (LMAA) pretreatment on biomass storage

A simpler pretreatment method using anhydrous ammonia has been developed by our group, which was designated as low-moisture anhydrous ammonia (LMAA). In this method anhydrous ammonia gas is contacted with biomass in an ammoniation reactor operated under relatively mild conditions, and then biomass is allowed to react with the adsorbed ammonia in a closed reactor. The adsorbed ammonia also provides anti-microbial effects for long-term storage and provides nitrogen for the microorganisms used in the fermentation process.

Lignocellulosic biomass such as corn stover typically can be harvested once a year in the fall, but not all of the harvested corn stover can be converted to in the desired products in the biorefinery within a few weeks after it is harvested. Long-term storage of the feedstock with minimal destruction of the available carbohydrates, for example, by microbial biodegradation, is highly desirable. Ammonia has been known to be effective against bacteria. It was reported that the antimicrobial effect of ammoniating allowed long-term storage of biomass with minimal biodegradation of carbohydrates.

In this study, corn stover with various moisture contents (10%-70%) was ammoniated, pretreated and then stored for 24 weeks. Chemical compositional changes of untreated and pretreated corn stover samples were periodically monitored during storage of biomass at 25°C.  Degradation of carbohydrates and changes of other components were of our interest. Enzymatic digestibility tests were also performed.