3-08: Bridging the gap: how can we reconcile optimal biomass conditions for comminution and handling with those for bioconversion?

Biomass assembly is an integral part of any bioconversion process, encompassing production, harvest, storage, transportation and handling. These steps have been optimized for minimal resource and energy inputs and maximum yields. Concurrently, the biomass conversion process has been well researched in every aspect, from pretreatment to hydrolysis to fermentation. Unfortunately, a gap often exists between biomass assembly and biomass conversion, as the optimum conditions for smooth biomass handling are rarely the same as the ideal conditions for pretreatment and bioconversion. For example, for minimal energy consumption, biomass should be as dry as possible before comminution. Conversely, it has been shown that high-moisture biomass provides higher ethanol yields than dried biomass following steam explosion pretreatment and bioconversion. How can we reconcile these two contradictory ideas? To find out, we sought to modify the moisture content of dried biomass after comminution in an attempt to regain the same yields that would have been achieved with fresh chipped biomass. This study compares ethanol yields after steam explosion and simultaneous saccharification and fermentation from air dried, fresh chipped, soaked and steamed hybrid poplar to see if the established benefit of using fresh chips can be achieved by artificially increasing the moisture of air-dried chips. The results of this study form the basis for better decision-making regarding the best treatment for biomass available in a given area at a given time. Understanding how to condition and alter biomass after comminution will allow us to bridge the gap between biomass assembly and conversion.