Characterization of chemical composition, milling properties and carbon dioxide diffusivity resulting from early harvest corn and corn stover

The increasing demand of corn as food and fuel sources has increased the competition for feedstock between livestock and ethanol industries. Developing an effective corn harvesting, storage and utilization system can help reduce the competition for the limited corn supply in the current period. The overall goal of this study was to examine the feasibility of early harvest of corn and corn stover and determine the implications of this proposed practice on corn processing characteristics, chemical composition and nutritive values. Effective diffusion coefficient of CO2 through bulk corn at different moisture contents and temperatures were measured to a better understand CO 2 movement during corn storage, which could help develop a CO2 monitoring system for corn storage.;Corn plants were harvested at different maturity stages in 2009 and 2010 and were quantitatively evaluated in terms of moisture contents, dry matter yields, compositions and processing characteristics of corn and corn stover. The dry matter yield of corn increased rapidly until reaching corn maturity and remained stable after maturity, with an average yield of 11.1 t/ha over the two year study. For corn stover, the two year average dry matter yield was 14.8 t/ha at the beginning of the study (filling stage) and decreased to 13.2 t/ha at corn physiological maturity and further decreased throughout corn dry down. Effects of corn harvest moisture content on dry grind ethanol processes were observed on fermentation characteristics. The final ethanol concentration from corn with harvest moisture content of 54% (110 days after corn planting, kernel dent stage) was 0.5 to 1.2 percentage points higher than that from mature corn with lower harvest moisture contents. Corn harvest moisture content affected compositions and nutritive values of corn, corn stover and dried distiller grain solubles (DDGS). As corn harvest moisture content decreased, neutral detergent fiber, acid detergent fiber and lignin concentrations in corn stover increased while crude protein concentrations decreased. These results showed that the whole corn plant could be most efficiently used if the corn and corn stover were harvested as soon as corn reached physiological maturity.;Early harvested corn poses a problem of storability due to its high moisture content. Effective CO2 diffusion coefficients in bulk corn at various temperatures (10, 20 and 30°C) and corn moisture contents (14.0, 18.8 and 22.2% w.b.) were determined to help develop a CO2 monitoring system for corn storage. The diffusion coefficient measurements were conducted using a diffusion cell surrounded by a water jacket, which was used to control the temperature of the bulk corn in the diffusion cell. A source term (CO 2 respiration rate) was introduced in the diffusion equation to account for the CO2 production by corn during the diffusion process. The corn respiration rate increased when temperature and corn moisture content increased. As respiration rate increased, it had a larger effect on the diffusion pattern when measuring the effective diffusion coefficient. The effective diffusion coefficients of CO2 through bulk corn ranged between 3.10 x 10-6 and 3.93 x 10-6 m2/s, depending on temperature and moisture contents. As temperature increased from 10 to 30°C, the diffusion coefficient of CO2 through bulk corn increased from 3.21 x 10-6 to 3.76 x 10 -6 m2/s, respectively. As corn moisture content increased from 14.0 to 18.8%, the effective diffusion coefficient through bulk corn decreased from 3.59 x 10-6 to 3.39 x 10-6 m2/s, respectively. There was no difference observed in the effective CO 2 diffusion coefficient when corn moisture content increased from 18.8 to 22.2%.