Harvesting, Drying, and Storing Grain Sorghum

Grain sorghum (milo) has been successfully produced in many areas of Kentucky and can be grown in alternating years with soybeans to replace corn in a crop rotation cycle. For most of the past 20 years, it has ranked fourth in production of all grain crops grown in the state and was valued at $1.16 and$1.53 million in 1999 and 2000, respectively. Rotating milo with soybeans can help control soybean cyst nematodes and other pests that suppress yield. It can provide higher yields than corn in dry years, especially on sandy soils. The feed/energy value of milo is similar to corn, so it has been used successfully in balanced rations for beef, poultry, and swine and as a feedstock for ethanol production (Hamman et al., 2001). In fact, the 2002 Farm Bill (USDA, 2002) encourages an increase in the production of grain sorghum because of its use as an ethanol feedstock and the current national interest in reducing foreign oil imports

Permeability of Corn, Soybeans, and Soft Red and White Winter Wheat as Affected by Bulk Density

Darcy’s law is a function of viscosity, permeability, and velocity and can be used to predict the airflow resistance in granular materials at low air velocities. Permeability also governs the magnitude of natural convection currents during periods of non-aerated grain storage. The permeability of corn, soybeans, soft white winter wheat, and soft red winter wheat were measured as a function of bulk density and moisture content. Air was passed through a column of grain and the flow rate and pressure drop measured. Bulk density and kernel density were also measured to determine the porosity of grain in the test column. Two filling methods were used to change the bulk density of grain by approximately 50 kg/m3, an increase of 7%. This resulted in a reduction in porosity of approximately 4 percentage points. However, permeability decreased by a maximum of 45%. Wheat had the lowest permeability (between 1.15 × 10-8 and 7.29 × 10-9 m2 or highest resistance coefficient between 1591 and 2510 Pa.s/m2, respectively, depending on bulk density and moisture content), while corn and soybeans were similar (permeability varied between 1.30 × 10-8 and 3.03 × 10-8 m2 or resistance coefficient between 1,408 and 604 Pa·s/m2, respectively). Experiments were conducted up to an air velocity of 0.0052 m/s that resulted in a Reynolds number of 2.5, which was slightly above the maximum air velocity expected during non-aerated grain storage. Nevertheless, Darcy’s law would be appropriate for predicting natural convection currents during non-aerated storage

Hydraulic Properties of Baled Switchgrass and Miscanthus

This study characterized the hydraulic properties within baled switchgrass ( Panicum virgatum L., variety Alamo) and miscanthus (Miscanthus x giganteus), thereby enabling a better understanding of moisture changes in baled biomass during on-farm storage and/or high-solids bioconversion. Fully saturated bales were drained by gravity, and the moisture content was determined over 60 h. The average initial moisture content ranged between 55.9% and 71.9% (w.b.) for switchgrass and between 60.5% and 73.9% (w.b.) for miscanthus bales depending on the dry bale density. As the bale drained by gravity, rapid leaching of water was observed within the first 0.1 h, with a reduction in moisture content of 7.3 and 7.0 percentage points (w.b.) for switchgrass and miscanthus, respectively. Leaching then continued at a steady rate until termination of the experiment, with further reductions of 4.3 and 4.4 percentage points (w.b.) for switchgrass and miscanthus, respectively. Final moisture contents after 60 h ranged from 45.8% to 58.3% for switchgrass and from 48.7% to 60% for miscanthus, with the higher moisture contents observed in the lowest density bales. Hydraulic conductivity tests were carried out with bales of switchgrass and miscanthus with a constant head system. The average saturated hydraulic conductivity ranged between 0.103 and 0.616 cm s-1 for baled switchgrass and between 0.219 and 0.658 cm s-1 for baled miscanthus depending on the bale density. The matric suction of baled switchgrass was also assessed at variable densities and moisture contents using the contact filter paper method. The van Genuchten parameters were found to range between 0.235 and 0.270 m-1 for α and between 5.415 and 10.345 for n, depending on the density. Infiltration tests were also carried out on baled switchgrass at variable densities and moisture contents using a minidisk infiltrometer. The curve-fitting parameters of Philip‘s two-term equation ranged between 0.086 x 10-6 and 0.779 x 10-6 cm s-1 for C1 and between 0.200 and 5.805 x 10-6 cm s-1/2 for C2, depending on the density and moisture content. The unsaturated hydraulic conductivity ranged between 0.019 and 0.272 cm s-1, while sorptivity ranged between 0.048 and 2.103 cm s-1/2, depending on the density and moisture content. These results provide data required to evaluate water flow through variable-density rectangular bales and indicate a potential to remove end-products of biomass conversion from baled biomass

Simulated Performance of Conventional High-Temperature Drying, Dryeration, and Combination Drying of Shelled Corn with Automatic Conditioning

Combination drying, based on computer simulation, was evaluated as an alternative drying technique to traditional high-temperature drying and dryeration. Simulation models of high-temperature crossflow drying and in-bin drying and conditioning were used to evaluate the performance of conventional crossflow drying and full-heat crossflow drying followed by dryeration or natural-air drying for Indianapolis, Indiana, and Des Moines, Iowa. Energy costs from propane, electricity, moisture shrink below the market moisture content, and dry matter loss were estimated to find the total average drying cost over 29 years. Dryeration and combination drying reduced the total drying cost by approximately 10% compared to conventional drying and cooling within the dryer at current economic conditions. The greatest benefit was an increase of 72 and 159% in drying capacity when dryeration and combination drying were used instead of conventional drying and cooling within the dryer, respectively. However, the economic return of combination drying could be improved by the development of natural-air drying techniques or controllers that would limit the predicted moisture shrink loss

Effect of Stover Fraction on Glucose Production Using Enzymatic Hydrolysis

Corn stover was fractionated into three fractions: cobs, stalks, and leaves and husks. The fractions were dried and ground through a 2 mm screen. Samples of the three fractions and whole corn stover with and without NaOH pretreatment were subjected to enzymatic hydrolysis in order to determine the effect of fractionation on glucose production. The average amounts of glucose released after 60 h of hydrolysis from pretreated cobs, leaves and husks, stalks, and whole stover were 0.50, 0.36, 0.28, and 0.36 g/g dry biomass, respectively. The average amounts of glucose released after 60 h of hydrolysis from nonpretreated cobs, leaves and husks, stalks, and whole stover were 0.32, 0.23, 0.17, and 0.20 g/g dry biomass, respectively. Pretreatment resulted in an average increase of 60% in glucose production for all fractions and whole stover. The effect of stover fraction type on glucose production was significant with and without pretreatment. By collecting the fractions of the corn stover with the highest glucose potential (all the cobs and 74% of the leaves and husks) and leaving the remaining fraction (26% of the leaves and husks, and all the stalks) in the field for erosion control, the glucose potential of the collected biomass would increase by 21%. This could represent a decrease of up to 17% in the cost of ethanol production. This indicates that fractionation and collection of the biomass with the highest glucose potential may produce a higher quality feedstock for glucose production

Reconditioning Corn and Soybeans to Optimal Processing Moisture Contents

Experimental trials were carried out to evaluate the technical feasibility of reconditioning overly dry corn and soybeans to optimal market and processing moisture contents. Data obtained from experimental trials were used to validate an aeration simulation model. This model was used to evaluate the feasibility of reconditioning soybeans and corn. Reconditioning of grain was feasible at low airflow rates (0.11 m3 min–1 t–1) over a six-month period when an automatic aeration controller was used. Using downflow aeration and monthly unloading of the bin allowed for the greatest net economic gain. Predicted reconditioning in Des Moines, Iowa, had a lower net economic gain than in Indianapolis, Indiana, based on 29 years of historic weather records

Evaluation of Fourier Transform Infrared Spectroscopy Measurements of Glucose and Xylose in Biomass Hydrolyzate

Measurement of sugars using traditional spectroscopic (UV/Vis) assays or high performance liquid chromatography (HPLC) can be time consuming and expensive. Alternative methods for measuring sugars after enzymatic hydrolysis of biomass would be convenient for screening potential biomass feedstocks and pretreatment methods. Fourier transform infrared spectroscopy (FTIR) has been utilized for measuring composition of various aqueous solutions and is evaluated here as an alternative to UV/Vis and HPLC assays. Solutions of glucose and xylose with concentrations between 0 and 1.5% w/v (total sugar content between 0 and 3.0% w/v) were used to build calibration curves for all three methods. A validation set of 10 samples of varying concentrations of glucose and xylose (between 0 and 1.5% w/v) were used to quantify the performance of the three measurement techniques. The FTIR assay was able to predict the glucose and xylose concentration with a standard error of prediction (SEP) of 0.03% (w/v), lower than the SEP for the HPLC (~0.06%) and UV/Vis (~0.07%) assays. The FTIR assay was also able to accurately measure the sugar concentration of wheat stover (raw and pretreated with sodium hydroxide) after enzyme hydrolysis, although all three techniques produced similar results

Development of a Finite-Element Stored Grain Ecosystem Model

An axisymmetric finite–element model was developed that predicts the heat, mass, and momentum transfer that occurred in upright corrugated steel storage structures due to conduction, diffusion, and natural convection using realistic boundary conditions. Weather data that included hourly total solar radiation, wind speed, ambient temperature, and relative humidity were used to model the temperature, moisture content, dry matter loss, and maize weevil development during storage with no aeration, and with ambient and chilled aeration. Periods of aeration were simulated assuming a uniform airflow rate through the grain mass. Heat and mass balances were used to calculate the temperature and absolute humidity in the headspace and plenum based on solar radiation, wind speed, ambient conditions, air infiltration, convective heat and mass transfer from the grain surface, and permeable boundaries that allowed natural convection currents to cross grain surfaces. A heat balance was used to estimate the wall temperature. The type of weather data in terms of solar radiation and frequency of data appear to be important when predicting the grain temperature, moisture content, dry matter loss, and maize weevil development

Validation of a Finite-Element Stored Grain Ecosystem Model

An axisymmetric finite–element model was validated with respect to predicting the heat, mass, and momentum transfer that occurred in upright corrugated–steel storage bins due to conduction, diffusion, and natural convection using realistic boundary conditions. Hourly weather data that included hourly total solar radiation, wind speed, ambient temperature, and relative humidity were used to model the corn temperature and moisture content during storage with no aeration, and with ambient and chilled aeration. Periods of aeration were simulated assuming a uniform airflow rate through the grain mass. Sixteen bins with a capacity of 11.7 t each and instrumented with temperature cables were available to validate the model using two years of measured corn temperatures and moisture contents during summer storage. The average standard error between the experimental and predicted temperatures was 2.4° C (1.1° C to 5.7° C range), and the standard error between experimental and predicted moisture contents was 0.7 percentage points. The average standard error was 1.5° C in three non–aerated bins with sealed plenums when corn temperature was predicted as a function of the natural convection equation. The predicted natural convection effect was not applicable unless the plenum was assumed sealed

Effect of Moisture Content and Broken Kernels on the Bulk Density and Packing of Corn

Shelled yellow dent corn samples were conditioned to three moisture content levels (12%, 15%, and 18% w.b.) and mixed with a prescribed amount of broken corn particles of known size (geometric mean diameter of 1.0, 1.4, 2.0, 2.8, and 4.0 mm) and concentration (2.5%, 5.0%, and 7.5% by weight) levels. The initial bulk density and grain compaction under simulated overburden pressure tests were determined for each sample. Uniaxial compression tests were performed for seven vertical pressure levels (3.4, 6.9, 14, 28, 55, 110, and 165 kPa) with a minimum of three replications each. Tests were performed at two locations with identical apparatus, which was fully described by Thompson and Ross (1983). These devices used compressed air injected beneath a rubber diaphragm to apply vertical pressure uniaxially to a volume of granular material. Deflections of the grain mass were measured with a dial gauge and were used to calculate changes in bulk density and grain packing. Statistical models were tested for the initial bulk density and packing factor as a function of moisture content, broken corn particle size, and broken corn concentration level and their interactions. For clean corn, the initial bulk density was inversely affected by grain moisture while packing increased slightly with grain moisture. For corn mixed with fines, the initial bulk density decreased with grain moisture and the interaction of broken corn particle size and concentration but increased with the interaction of grain moisture and concentration of fines. Packing of corn mixed with fines increased slightly with grain moisture and broken corn concentration. For a given pressure, the predicted bulk density from the developed model was within 4% of the observed value, which was within the variation among test replications and may in fact represent observed differences in bulk density caused by bin loading methods that have been reported by other engineers. The results can improve predictions by WPACKING, the ASAE standard for estimating capacities of cylindrical grain storage structures