Ronald L. Belyea

The Future of Coproducts From Corn Processing

Increased demand for ethanol as a fuel additive has resulted in dramatic growth in ethanol production. Ethanol is produced from corn by either wet milling or dry-grind processing. In wet milling, the corn kernel is fractionated into different components, resulting in several coproducts. Wet-milling plants are capital intensive because of equipment requirements; they produce large volumes of ethanol and are corporate owned. In dry-grind processing, the corn kernel is not fractionated and only one coproduct, distillers’ dried grains with solubles (DDGS), is generated. Dry-grind plants require less equipment and capital than wet mills. They generate smaller volumes of ethanol, are producer owned, and add direct benefits to rural economies. Most of the increase in ethanol production during the past decade is attributed to growth in the dry-grind industry. The marketing of coproducts provides income to offset processing costs. For dry-grind plants, this is especially important, because only one coproduct is available. Several issues could affect DDGS marketing. The increasing volume of DDGS accompanying ethanol production could reduce market value; high phosphorous content could limit the use of DDGS, because of animal waste disposal issues. Water removal is a costly processing step and affects the economics of ethanol processing. Technologies to remove germ and fiber from DDGS could produce a new coproduct suitable for feeding to nonruminants; this would expand the markets for DDGS. Reducing phosphorus in DDGS would sustain markets for conventional DDGS. The development of more efficient methods of water removal would increase the efficiency of ethanol processing and reduce the costs of processing. New technologies could contribute to greater stability of dry-grind plants.

Characterization of dairy waste streams, current treatment practices, and potential for biological nutrient removal

Abstract Fifteen milk processing plants in the Upper Midwest of the United States participated in a study to obtain information on general process operation, waste generation and treatment practices, chemical usage, and wastewater characteristics. Long term data on wastewater characteristics were obtained for 8 of the 15 dairy plants, and a 24-h composite wastewater sample was characterized in detail for each plant. Wastewater flow rates and characteristics varied greatly among and within plants and were not easily predictable even when detailed information on processing operations was available. In addition, the contribution of milk and milk products to the waste streams was underestimated by plant operators. The use of caustic soda, phosphoric acid, and nitric acid for cleaning had a significant impact on wastewater characteristics, despite the implementation of changes in chemical usage practices during recent years. In particular, the use of phosphoric acid based cleaning products has been reduced to eliminate or decrease discharge fines. It was determined that most of the on site treatment facilities require renovations and/or operational changes to comply with current and future discharge regulations, especially with respect to nutrient (nitrogen and phosphorus) levels in their waste streams. It was concluded that biological nutrient removal of dairy wastewaters should be feasible given the relatively high concentrations of easily degradable organics, the generally favorable organic matter to total phosphorus ratio, and the very favorable organic matter to nitrogen ratio.

Comparison of modified dry-grind corn processes for fermentation characteristics and DDGS composition.

ABSTRACT Three different modified dry-grind corn processes, quick germ (QG), quick germ and quick fiber (QGQF), and enzymatic milling (E-Mill) were compared with the conventional dry-grind corn process for fermentation characteristics and distillers dried grains with solubles (DDGS) composition. Significant effects were observed on fermentation characteristics and DDGS composition with these modified dry-grind processes. The QG, QGQF, and E-Mill processes increased ethanol concentration by 8–27% relative to the conventional dry-grind process. These process modifications reduced the fiber content of DDGS from 11 to 2% and increased the protein content of DDGS from 28 to 58%.

Separation of Fiber from Distillers Dried Grains with Solubles (DDGS) Using Sieving and Elutriation

ABSTRACT A process was developed to separate fiber from distillers dried grains with solubles (DDGS) in a dry-grind corn process. Separation of fiber from DDGS would provide two valuable coproducts: 1) DDGS with reduced fiber, increased fat, and increased protein contents; and 2) fiber. The process, called elusieve process, used two separation methods, sieving and elutriation, to separate the fiber. Material carried by air to the top of the elutriation column was called the lighter fraction and material that settled to the bottom of the column was called the heavier fraction. We evaluated the compositions of fractions produced from sieving and elutriation. Two commercial samples of DDGS were obtained from two dry-grind corn plants. Sieving over four screens (869, 582, 447, and 234 μm openings) created five size categories. The two smallest size categories contained >40% (w/w) of the original DDGS and had reduced fiber and increased protein and fat contents relative to the original DDGS. Elutriation of the...

Variability in the nutritional quality of distillers solubles

Abstract Use of ethanol in fuels has led to increased production of industrial ethanol, and consequently of a coproduct, distillers solubles (DS). While DS from beverage ethanol processing have been shown to be valuable as animal foods, there are few data on the nutritional value of DS from industrial ethanol. The purpose of this study was to obtain nutritional data on the latter. Samples of DS were obtained from a corn wet milling/ethanol plant during five periods of 5–6 days each and analysed for nutrient content. Nutritional value varied with periods. Available energy in DS was lower than for corn. Most amino acids were in high concentrations, relative to many feeds, but digestibilities of several essential amino acids were low. DS have potential as food for non ruminants, but high nutrient variability, low amino acid digestibility and dewatering difficulties have to be addressed. Feeding trials will be necessary to establish practical dietary limits.

REMOVAL OF FIBER FROM DISTILLERS DRIED GRAINS WITH SOLUBLES (DDGS) TO INCREASE VALUE

This study was undertaken to investigate the possibility of using air aspiration to remove fiber from distillers dried grains with solubles (DDGS), produced from fuel ethanol and beverage alcohol cereal grain dry–grind processes. The aspirated fraction was called “aspirated DDGS” and the remaining fraction (original DDGS without the aspirated fraction) was called “residual DDGS.” Aspirated DDGS fractions were analyzed for individual and total phytosterol composition. Phytosterols are high–valued nutraceutical compounds that can be recovered from grain fiber fractions. The residual DDGS (original DDGS after the removal of fiber) was analyzed for fat, protein, neutral detergent fiber, acid detergent fiber, and ash content. The study showed limited success in removal of the fiber from the original DDGS fraction. Fiber content was only slightly enriched in the aspirated DDGS fraction compared to the residual DDGS fractions. Slightly better results (in terms of fiber enrichment) were seen with DDGS samples from certain dry–grind plants compared to the DDGS samples from other plants. These differences could be due to the differences in the milling/processing conditions of the plants. Although slight enrichment of fiber was obtained in the aspirated DDGS fraction as compared to the original DDGS, no significant enrichment of the phytosterols was noticed in the aspirated DDGS fraction. Due to aspiration, slight enrichment of oil and protein was observed in the residual DDGS fraction compared to the original DDGS. The increased oil and protein and decreased fiber content of the residual DDGS could result in increased market value of the residual DDGS.

Economics of Fiber Separation from Distillers Dried Grains with Solubles (DDGS) Using Sieving and Elutriation

ABSTRACT Separation of fiber from distillers dried grains with solubles (DDGS) provides two valuable coproducts: 1) enhanced DDGS with reduced fiber, increased fat and increased protein contents and 2) fiber. Recently, the elusieve process, a combination of sieving and elutriation was found to be effective in separating fiber from two commercial samples of DDGS (DDGS-1 and DDGS-2). Separation of fiber decreased the quantity of DDGS, but increased the value of DDGS by increasing protein content and produced a new coproduct with higher fiber content. Economic analysis was conducted to determine the payback period, net present value (NPV), and internal rate of return (IRR) of the elusieve process. The dependence of animal foodstuff prices on their protein content was determined. Equipment prices were obtained from industrial manufacturers. Relative to crude protein content of original DDGS, crude protein content of enhanced DDGS was higher by 8.0% for DDGS-1 and by 6.3% for DDGS-2. For a dry-grind plant proc...

Element concentrations of dry-grind corn-processing streams

The dry-grind corn process is one of two technologies used to convert corn into ethanol. In his process, all kernel components are processed through several sequential steps, including fermentation. Only one coproduct (distillers’ dried grains with solubles [DDGS]) is available for marketing. DDGS provide income to offset costs of processing; issues that affect marketing have implications in the economic viability of dry-grind plants. Two issues relate to elements in DDGS: high concentrations and excessive variation. Data on element concentrations in dry-grind processing streams could be helpful in addressing these concerns. The objective of this study was to determine element concentrations in primary process streams from dry-grind plants. Samples of corn, ground corn, beer, wet grains, syrup, and DDGS were obtained from nine dry-grind plants, and element concentrations were determinined. The concentrations of most elements in corn were not different among processing plants and were similar to published data. However, for the processing streams, there were differences in several element concentrations among processing plants. The concentrations of most elements in beer were about three times those of corn, due to the disappearance of starch during fermentation. Syrup had the highest element concentrations. Variations in element contents of DDGS and parent streams were due to processing conditions and not corn. Appropriate processing of thin stillage (the parent stream of syrup) could reduce the element content of DDGS.

PARTICLE SIZE DISTRIBUTIONS OF GROUND CORN AND DDGS FROM DRY GRIND PROCESSING

Ethanol production has increased in the past decade as a result of growth in the dry grind industry. In the dry grind process, the first step is grinding of corn. The particle size of the resulting ground corn can affect the fermentation process and the particle size of dried distillers’ grains with solubles (DDGS), a coproduct of dry grind processing. Few data are available that characterize particle size distributions of ground corn or DDGS. The objective was to determine particle size distributions of ground corn and DDGS. Samples of ground corn and DDGS were obtained from nine dry grind plants; particle size distribution, geometric mean diameter (dgw) and geometric standard deviation (Sgw) were determined. The dgw of ground corn and of DDGS were not different among processing plants. The overall mean dgw of ground corn was not different from that of DDGS. Most of the ground corn (80 g/100 g) and DDGS (70 g/100 g) were recovered in the three largest particle size categories. The particle size distributions of ground corn were not correlated (r < 0.35) to particle size distributions of DDGS.

Effect of pH on Fouling Characteristics and Deposit Compositions in Dry-Grind Thin Stillage

ABSTRACT Dry-grind corn processing facilities produce ethanol, carbon dioxide, and distillers dried grains with solubles (DDGS). To produce DDGS, dry-grind corn processors concentrate thin stillage in multieffect evaporators. Concentration of thin stillage uses large amounts of energy, and efficient operation is important for long-term economic stability of the industry. Little data are available on fouling of evaporators during thin stillage concentration. We evaluated how thin stillage pH and acid type used during pH adjustment affected fouling as measured by induction period, fouling rate, and deposit composition. Using an annular fouling apparatus, fouling tests were conducted at pH 3.5, 4.0, and 4.5. In a second experiment, we used two types of acid, HCl or H2SO4, to adjust thin stillage to pH 3.5. Induction periods were shorter at pH 3.5 than at pH 4.0 or 4.5. As pH increased, fouling deposit protein decreased and ash increased. Concentrations of most elements, including P, Ca, Mg, Mn, and K, increa...