SORPTION EQUILIBRIUM MOISTURE CHARACTERISTICS OF SELECTED CORN STOVER COMPONENTS
Corn stover equilibrium moisture isotherms were developed to aide biomass engineering of consistent, 
uniform-quality feedstock supplies for renewable bioenergy and bioproducts. Equilibrium moisture content (EMC) and 
equilibrium relative humidity (ERH) sorption data of corn leaf, stalk skin, and stalk pith were experimentally determined using 
the static gravimetric method at six temperatures ranging from 10°C to 40°C and at ten ERH values ranging from 0.11 to 
0.98. The greatest EMC values for corn leaf and stalk pith generally corresponded with ERH below and above 0.90, 
respectively, at all temperatures. Only at some intermediate ERH range at 20°C to 40°C was stalk skin EMC greater than 
stalk pith EMC. Corn stover components followed a type II isotherm typically observed among food materials. EMC of all 
components was proportional to ERH and inversely proportional to temperature. Observed EMC ranges were 3.9% to 56.4%, 
3.1% to 41.1%, and 2.7% to 71.5% dry basis (d.b.) for corn leaf, stalk skin, and stalk pith, respectively. Calculated whole-stalk 
EMC values ranged from 3.1% to 49.2% d.b. Isotherm data were fitted with the EMC model of Henderson, and modified 
versions of Henderson, Chung-Pfost, Halsey, Oswin, and Guggenheim-Anderson-deBoer. The modified Oswin model (R2 > 
0.98; F > 2085) followed by the modified Halsey model (R2 > 0.97; F > 1758) produced the best fit for corn stover components 
studied. The Henderson, modified Henderson, and modified Chung-Pfost models were not suitable since these models did not 
produce randomized residuals. The modified Oswin model (R2 = 0.99; F = 6274) best described the stalk EMC. Results have 
practical applications in corn stover collection method and timing; process handling, grinding, and drying requirements; 
transportation efficiency of dry matter; and necessary storage environment, shelf life, and potential microorganism safety 
hazards. For example, results indicated that higher EMC values for corn stover leaf may result in greater propensity for the 
onset of mold growth and may determine minimal storage requirements or potential advantages in separating leaf from stalk 
fractions.