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Water vapor adsorption on torrefied corn stover

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2012 Dallas, Texas, July 29 - August 1, 2012  121337123.(doi:10.13031/2013.41745)
Authors:   Dorde Medic, Matthew Darr, Ajay Shah, Sarah Rahn
Keywords:   equilibrium moisture content, torrefaction, microbial degradation, corn stover, hydrophobicity

The equilibrium moisture content (EMC) of biomass affects transportation, storage, downstream feedstock processing, and the overall economy of biorenewables production. Torrefaction is a thermochemical process conducted in the temperature regime between 200 and 300C under an inert atmosphere that, among other benefits, aims to reduce the innate hydrophilicity and susceptibility to microbial degradation of biomass. The EMC of raw corn stover, along with corn stover thermally pretreated at three temperatures, was measured using the static gravimetric method at equilibrium relative humidity (ERH) and temperatures ranging from 10 to 98% and from 10 to 40C, respectively. Microbial degradation of the samples was tested at 97% ERH and 30C. Fiber analyses were conducted on all samples. In general, torrefied biomass showed an EMC lower than raw biomass, which implied an increase in hydrophobicity. Corn stover torrefied at 250 and 300C had negligible dry matter mass loss due to microbial degradation. Fiber analysis showed a significant decrease in hemicellulose content with the increase in pretreatment temperature, which might be the reason for the hydrophobic nature of torrefied biomass. The outcomes of this work can be used for torrefaction process optimization, and decision-making regarding raw and torrefied biomass storage and downstream processing.

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