Severe biomass pretreatment, such as high acid concentration, temperature, or retention times, are often needed to prepare biomass for saccharification. Unfortunately, high severities result in the production of toxic byproducts, which are, among others, degradation products that stem from the decomposition of glucose and xylose into hydroxymethylfurfural (HMF) and furfural, respectively. It is well known in the community that HMF and furfural inhibit enzymatic hydrolysis and fermentation. HMF and furfural are usually removed from the pretreated biomass by washing with successive volumes, but this washing step implies colossal water usage that will be difficult to implement on a commercial (or technology deployment) scale. On the other hand, the pretreatment step cannot be omitted from biochemical processing because, without pretreatment, the expensive enzymes cannot access and hydrolytically cleave complex carbohydrates into coveted monomeric sugars. The catch-22 around pretreatment puts biochemically-based manufacturing processes in a bind, and there is a persistent knowledge gap as to how to proceed.<br/><br/>In order to reduce pretreatment severities, thereby increasing enzyme and fermentation efficiencies, storage could be used prior to pretreatment to loosen the plant cell wall, facilitating sugar release. By reducing pretreatment severities, degradation product concentrations could be minimized, decreasing the volumes of water necessary for the bioprocess. Results from 65-day field stored switchgrass (with barn storage as control) pretreated with dilute acid will be presented. Results showed that field storage decreased production of HMF, but increased production of furfural relative to barn storage. Results on switchgrass storage of round bales seeded with <i>Pleurotus ostreastus</i> and then pretreated with liquid hot water will also be presented. It is possible that biomass storage could become an element of the complex feedstock supply chain that could be used to minimize overall pretreatment severity, minimizing degradation product generation and overall water requirements of the bioprocess.

Decreasing the severity of chemical pretreatment processes of switchgrass through storage

249th National Meeting (2015)

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