Dry-grind Ethanol Plant Research Articles

Impact of Heat Exchanger Fouling in Bioethanol Plants

Bioethanol plays a major role in improving the sustainability of a carbon-intensive sector such as transportation. With a pressing need in the industry to reduce carbon intensity of the ethanol production itself, it is of paramount importance ensuring that thermal systems are as efficient as possible. One of the biggest challenges that leads to significant operational issues, extra energy and water consumption, unplanned plant shutdowns and unnecessary CO2 emissions is fouling, the progressive deposition of low thermal conductivity material on thermal surfaces. This unwanted deposition reduces the thermal efficiency of key equipment, including heat exchangers and evaporators and increases pressure drops. In this paper, a mathematical model for the most energy-intensive section of a typical 50 MGY dry-grind ethanol plant is developed to assess the economic and environmental impact of fouling. The model includes double effect evaporators integrated with the beer column and two reboilers and allows quantifying the Key Performance Indicators under different combinations of fouling rates, operating conditions and cleaning effectiveness. Results show that even if regular cleaning cycles are performed, following current industry standards, the impact of fouling is still significant, with emissions of 15,435 ton CO2/year (81.67g CO2/l), additional energy of 70,809 MWh/year (0.38 kWh/l), additional water use of 106,738 m3/year (0.56l/l), and additional costs of 3.53 MM$ per year (0.02 $/l). Moreover, by optimising the selection of cleaning agents, costs can be reduced up to 65-70% while water consumption, energy use and emission release can be curbed by 70 to 80%. Other strategies to mitigate fouling (e.g. increasing steam pressure) were also identified and discussed.

Oil Recovery from Dry Grind Ethanol Plant Coproducts Using Ethanol

Corn ethanol bio-refineries are seeking economic processing strategies for recovering oil from their coproducts. The addition of ethanol can be an efficient method to recover the oil from the coproducts as the industry has available ethanol. This study considered the effects of ethanol on oil recovery from distillers’ dried grains with solubles (DDGS) and oil partitioning from whole stillage (WS) on a laboratory scale. Ethanol was added with original and heavier fraction DDGS in different temperatures (room temperature ~20 °C, 30 °C, 40 °C, and 50 °C) and solids loadings (20%, 30%, and 40%), and their effects on oil recovery were evaluated. The whole stillage was incubated with ethanol at room temperature (~20 °C) and 50 °C separately to analyze WS’s oil distribution in the liquid and solid phases. The amount of recovered oil from the original and heavier fractions of DDGS varies from 25–45% and 45–70%, respectively, with an increment of temperature. Increasing solids loadings up to 30% had no effect on oil recovery from either DDGS sample. Ethanol treatment in WS resulted in 8–10% higher wet yield of liquid fraction and 17–20% of oil increase in liquid fraction than the control treatment. It is also notable that temperature positively impacted oil partitioning from WS. The results showed that ethanol could improve oil recovery from DDGS and oil partition in WS by varying different process conditions. This outcome is beneficial to ethanol plants to increase corn oil yield using their existing setup and in-situ product.

Evaluation of dietary corn fermented protein on growth performance and haemato‐immunological parameters of the Pacific white shrimp Litopenaeus vannamei

The use of corn fermented protein (CFP) as a sustainable and functional ingredient in a shrimp diet formulation was evaluated. Four isonitrogenous and iso-lipidic practical diets were formulated to contain 0%, 6%, 12% and 18% of CFP obtained from mechanical separation of protein post distillation within dry-grind ethanol plants utilizing separation technology from Fluid Quip Technology. The 18% CFP diet was formulated to partially replace the use of fish meal (FM) and soybean meal (SBM) as well as completely replace the use of corn gluten meal (CGM). A total of 300 shrimp with average initial body weight of 2.02 ± 0.03 g were randomly stocked into four groups, with five replicates per group per treatment and 15 shrimp per aquaria tank. The results showed that in general, CFP could enhance the growth performance of shrimp. The use of 6% and 12% inclusion level of CFP resulted in a significant increase in final biomass, final mean weight (FMW), thermal growth coefficient (TGC) and superior feed conversion ratio (FCR) compared with the control diet (p < 0.05). Reducing the amount of FM from 10 to 7.5% and supplemented with CFP still have better FMW, weight gain (WG), FCR and TGC compared with the control treatment. No significant differences of total haemocyte count (p = 0.2619) and lysozyme activity (p = 0. 1185) were observed. In addition, the protein content and protein retention efficiency showed no significant differences (p > 0.05) among the treatments. These results suggest that 18% corn fermented protein can be utilized as an alternative protein source without compromising the growth and health condition of shrimp L. vannamei.

Pellet Quality of Corn-Based DDGS

The rapid growth of corn-based dry grind ethanol plants over the past decade in the US has resulted in a great increase in production of the coproduct DDGS (distillers dried grains with solubles). Since some physical properties like low bulk density and poor flowability can impact the market potential of DDGS, pelleting of DDGS can be one of the easiest ways to improve this situation. Pellet quality is the focus of this project. The pelleting process was conducted with three initial DDGS moisture contents and two different dies; a total of six runs were completed to produce DDGS pellets. The physical qualities of pelleted DDGS were determined by measuring durability, bulk density, angle of repose, and color of the pellets. The results showed that the durability ranged from 42% to 89%, the highest pellet durability occurred when the moisture content was 20% db and the die diameter was 1/8 in. The bulk density increased when the DDGS moisture content decreased, and the highest bulk density was observed when the moisture content was 10% db and the die diameter was 1/8 in.

Determination of in vitro dry matter, protein, and fiber digestibility and fermentability of novel corn coproducts for swine and ruminants.

New processes are being used in some dry-grind ethanol plants in the United States and Brazil to improve ethanol yield and efficiency of production while also providing nutritionally enhanced corn coproducts compared with conventional corn distillers dried grains with solubles (DDGS). The objectives of this study were to determine the chemical composition and in vitro digestibility of 5 conventional corn DDGS sources and 10 emerging novel corn coproducts for swine and ruminants, and compare coproducts produced using similar processes in the United States and Brazil. Chemical composition, on a dry matter (DM) basis, among the 15 coproducts ranged from 18.5% to 54.7% for crude protein (CP), 12.3% to 51.4% for neutral detergent fiber (NDF), 1.6% to 8.6% for acid detergent fiber, 4.7% to 12.3% for ether extract, and 1.6% to 8.6% for ash. For swine, in vitro hydrolysis of DM and CP were greater (P < 0.01) for the three U.S. corn DDGS sources compared with the two Brazilian corn DDGS sources, but in vitro fermentability of DM was comparable (P > 0.05) among all sources except one U.S. DDGS source that had less fermentable DM. High-protein and yeast dried distillers grains (Ultramax, UM; StillPro, SP) coproducts also had comparable (P > 0.05) DM fermentability for swine, but UM coproducts had greater (P < 0.01) DM and CP hydrolysis compared with SP. High-protein distillers dried grains (HP-DDG) from Brazil had greater (P < 0.01) DM and CP hydrolysis, but less (P < 0.01) DM fermentability for swine than HP-DDG produced in the United States, using the same process. For ruminants, total DM digestibility was greater (P < 0.01) in conventional DDGS sources from the United States compared with the two DDGS sources from Brazil. Total protein digestibility for ruminants was comparable and above 81% for all coproducts except for a DDGS source from Brazil, a HP-DDG source from the United States, and a UM sample. Interestingly, the corn fiber + solubles coproduct had not only relatively high digestibility of NDF (67.9%), DM (91.6%), and total CP (81.9%) for ruminants, but it also had relatively high total tract digestibility of DM (86.2%) and CP (69.9%) for swine. These results suggest that nutrient digestibility of conventional DDGS sources produced in the United States appear to be greater than corn Brazilian DDGS sources, but new process technologies being implemented in ethanol and coproduct production in both countries can enhance the nutritional value of corn coproducts for both swine and ruminants.

Optimization of two-stage pretreatment for maximizing ethanol production in 1.5G technology

Two-stage pretreatment conditions were optimized to convert corn fiber, separated from whole stillage in a corn dry grind ethanol plant, to fermentable sugars via hydrolysis. Liquid hot water pretreatment (25% solids) at 180 °C for 10 min, followed by three cycles of disk milling, provided maximum glucose, xylose, and arabinose yields of 88.5%, 41.0%, and 30.4% respectively after hydrolysis with Cellulase I. The glucose, xylose, and arabinose yields with Cellulase II at optimum conditions were 94.9%, 74.2%, and 66.3%, respectively. SSF of corn fiber using engineered yeast, with both Cellulase I and II, provided maximum ethanol concentrations of 2.13% and 2.73% (v/v). The protein content in the residual solid after fermentation was 47.95% and 52.05% for Cellulase I and II, respectively. This technology provides additional ethanol in a dry grind plant by converting corn fiber into ethanol and increases the protein content of DDGS, thereby improving the quality.

Bioprocessing and technoeconomic feasibility analysis of simultaneous production of d-psicose and ethanol using engineered yeast strain KAM-2GD

The objective of this study was to analyze the processing and technoeconomic feasibility of coproduction of d-psicose and ethanol in a modified dry grind ethanol process. The yeast strain was constructed by expressing d-psicose 3-epimerases (DPE) in Sachharomyces cerevisiae. The strain was capable of converting d-fructose to d-psicose at 55 °C with a conversion efficiency of 26.6%. A comprehensive process model for modified dry grind ethanol plant with 396,000 MT/yr corn processing capacity was developed using SuperPro Designer. Predicted ethanol and d-psicose yields were 390.4 L and 75.3 kg per MT of corn, with total annual production of 154.6 million L and 29,835 MT respectively. The capital investment for the plant was estimated as 150.3 million USD with total operating cost of 85.2 million USD/yr. The unit production cost and minimum selling price of d-psicose with an internal rate of return of 15% were calculated as $0.43/kg and $1.29/kg respectively.

A Statistical Optimization Study on Dilute Sulfuric Acid Pretreatment of Distillers Dried Grains with Solubles (DDGS) As a Potential Feedstock for Fermentation Applications

Distillers dried grains with solubles (DDGS) are co-product of dry-grind ethanol plant, which can be used as a feedstock for fermentation, e.g. for biofuels or other value-added products. However, DDGS loading is a critical factor in the pretreatment, hydrolysis, and fermentation, where the low DDGS loading lowers sugar concentration in the hydrolysate and yields low product concentrations, which can result in high energy cost at the recovery step, while too high loading may have inhibitory effects on the microbial growth during fermentation. Therefore, an optimal DDGS loading needs to be determined at the pretreatment step for high sugar yields. In this study, dilute sulfuric acid pretreatment of DDGS was optimized to obtain the high release of sugars with the use of high DDGS loading at an appropriate acid concentration. An experimental design was constructed with the Box-Behnken response surface method using the ranges of 5–20% (wt) DDGS, 1–5% (wt) H2SO4, and 20–60 min pretreatment times at a constant temperature of 120 °C. The results revealed the highest yields of sugars (0.39 g/g) at 20% DDGS, 5% (wt) H2SO4, and 120 °C after 1 h. The results justify complete hydrolysis of hemicellulose and residual starch fractions and provide sufficient amount of sugars for the fermentation process.

Maize Proximate Composition and Physical Properties Correlations to Dry-Grind Ethanol Concentrations

Dry-grind ethanol plants incur economic losses because of seasonal variations in ethanol yields. One possible cause associated with ethanol yield variability is incoming grain quality. There is little published information on factors causing variation in dry-grind ethanol concentrations. The objective of this study was to determine relationships between rapidly measurable corn quality attributes (physical parameters and chemical composition) and dry-grind ethanol concentrations. Corn samples obtained from a Midwestern ethanol plant were analyzed for physical quality parameters (test weight, kernel weight, true density, percent stress cracks, and moisture content) and composition (starch, protein, oil, and soluble sugars contents) and then processed with a laboratory-scale dry-grind procedure. There were significant (P < 0.05) variations in corn quality parameters and ethanol concentrations. Correlation coefficients were significant (P < 0.05) but low (–0.50 < r < 0.50) between starch content and final eth...

Validation of prediction equations for apparent metabolizable energy of corn distillers dried grains with solubles in broiler chicks

An experiment consisting of 3 nearly identical trials was conducted to determine the AMEn content of distillers dried grains with solubles (DDGS) to validate 4 previously published prediction equations for AMEn of corn DDGS in broilers. In addition, prior research data were used to generate a best-fit equation for AMEn based on proximate analysis. Fifteen samples of DDGS ranging in ether extract (EE) from 4.98 to 14.29% (DM basis) were collected from various dry-grind ethanol plants and were subsequently fed to broiler chicks to determine AMEn content. A corn-soybean meal control diet was formulated to contain 15% dextrose and test diets were created by mixing the control diet with 15% DDGS at the expense of dextrose. In each trial, male Ross × Ross 708 chicks were housed in grower battery cages and received a common starter diet until the experimental period. Each cage was randomly assigned to 1 of the dietary treatments (trial 1 and trial 2: control + 6 test diets, 13 replicates per diet; trial 3: control + 3 test diets, 12 replicates per diet). Experimental diets were fed over a 6-d acclimation period, followed by a 48-h total excreta collection period. On a DM basis, AMEn of the 15 DDGS samples ranged from 1,975 to 3,634 kcal/kg. Analyses were conducted to determine gross energy, CP, EE, DM, starch, total dietary fiber, neutral detergent fiber, crude fiber (CF), acid detergent fiber, and ash content of the DDGS samples. All results were reported on a DM basis. Application of the 4 equations to the validation data resulted in root mean square error (RMSE) values of 335, 381, 488, and 502 kcal/kg, respectively. Least absolute shrinkage and selection operator technique was applied to proximate analysis data for 30 corn coproducts adapted from prior research and resulted in the following best-fit equation: [AMEn (kcal/kg) = 3,673 – (121.35 × CF) + (51.29 × EE) – (121.08 × ash); P < 0.01; R2 = 0.70; R2adj = 0.67; RMSE = 270 kcal/kg]. The RMSE values obtained through validation were not consistent with the expectation of predictive performance based on internal measures of fit for each equation. These results indicated that validation is necessary to quantify the expected error associated with practical application of each individual prediction equation to external data.

Microbial community composition is consistent across anaerobic digesters processing wheat-based fuel ethanol waste streams

Biochemical methane potential (BMP) assays were conducted on byproducts from dry-grind wheat-based ethanol plants amended with feedlot manure at two input ratios. Whole stillage (WST), thin stillage (TST) and wet cake (WCK) were tested alone and with 1:1 and 2:1 ratios (VS basis) of byproduct:feedlot manure in bench-scale batch reactors. The addition of manure increased both the rate and consistency of methane production in triplicate reactors. In addition, digesters co-digesting thin stillage and cattle manure at 1:1 and 2:1 stillage:manure produced 125% and 119% expected methane based on the biomethane potential of each substrate digested individually. Bacterial community analysis using universal target amplification and pyrosequencing indicated there was a numerically dominant core of 42 bacteria that was universally present in the reactors regardless of input material. A smaller-scale analysis of the archaeal community showed that both hydrogenotrophic and acetoclastic methanogens were present in significant quantities.

Economics of Implementing Elusieve Process for Fiber Separation from Corn Flour in Dry Grind Ethanol Plant

Economics of Implementing Elusieve Process for Fiber Separation from Corn Flour in Dry Grind Ethanol Plant

Apparent metabolizable energy and prediction equations for reduced-oil corn distillers dried grains with solubles in broiler chicks from 10 to 18 days of age

An experiment consisting of 2 identically designed trials was conducted to determine the nutrient composition and AMEn content of distillers dried grains with solubles (DDGS) to develop prediction equations for AMEn in broilers. Fifteen samples of DDGS ranging in ether extract (EE) from 3.15 to 13.23% (DM basis) were collected from various dry-grind ethanol plants and were subsequently fed to broiler chicks to determine AMEn content. A corn-soybean meal control diet was formulated to contain 15% dextrose, and test diets were created by mixing the control diet with 15% DDGS at the expense of dextrose. In each trial, 672 male Ross × Ross 708 chicks were housed in grower battery cages with 7 birds per cage (0.06 m2/bird) and received a common starter diet until 10 d of age. Each cage was randomly assigned to 1 of 16 dietary treatments, with 6 replicate pens per treatment. Experimental diets were fed over a 6-d acclimation period from 10 to 16 d of age, followed by a 48-h total excreta collection period. Gross energy (GE) and CP of the experimental diets and excreta were determined to calculate AMEn for each DDGS sample. On a DM basis, AMEn of the 15 DDGS samples ranged from 1,869 to 2,824 kcal/kg. Analyses were conducted to determine the GE, CP, EE, DM, starch, total dietary fiber (TDF), neutral detergent fiber (NDF), acid detergent fiber (ADF), and ash content of the DDGS samples. Stepwise regression resulted in the following best-fit equation for AMEn (DM basis) based on the adjusted coefficient of determination (R2adj), SE, and prediction error sum of squares (PRESS): AMEn, kcal/kg = −12,282 + (2.60 × GE) + (89.75 × CP) + (125.80 × starch) – (40.67 × TDF; R2adj = 0.86; SE = 98.76; PRESS = 199,819; P ≤ 0.001). These results indicated that the composition of DDGS with variable EE content may be used to predict AMEn in broiler chicks.

Use of treated effluent water in ethanol production from cellulose

The bioethanol industry exerts a significant demand on water supplies. Current water consumption rate in corn dry grind ethanol plants is (11–15) dm3 m−3 of ethanol produced and (23–38) dm3 m−3 for cellulosic ethanol plants. The main goal of this study was to examine the feasibility of use of treated wastewater effluent in place of potable freshwater for cellulosic ethanol production. The effects of using two different types of filtered treated effluent; Bloomington- Normal, IL (Residential type) and Decatur, IL (Industrial/Residential Mix type); on the rate of fermentation and final ethanol yield from a pure cellulosic substrate were evaluated. Characterization analysis of both effluent water samples indicated low concentration of toxic elements. Final ethanol concentrations obtained with Bloomington- Normal and Decatur effluent and with a control treatment using de-ionized water were similar, resulting in 360 g kg−1 (0.36 g g−1), 370 g kg−1 (0.37 g g−1) and 360 g kg−1 (0.36 g g−1), respectively. These findings suggest that with proper characterization studies and under appropriate conditions, the use of treated effluent water in cellulosic ethanol production is feasible.

Determination and prediction of digestible and metabolizable energy from chemical analysis of corn coproducts fed to finishing pigs1

Twenty corn coproducts from various wet- and dry-grind ethanol plants were fed to finishing pigs to determine DE and ME and to generate equations predicting DE and ME based on chemical analysis. A basal diet comprised corn (97.05%), limestone, dicalcium phosphate, salt, vitamins, and trace minerals. Twenty test diets were formulated by mixing the basal diet with 30% of a coproduct, except for dried corn solubles and corn oil, which were included at 20 and 10%, respectively. There were 8 groups of 24 finishing gilts (n = 192; BW = 112.7 ± 7.9 kg). Within each group, gilts were randomly assigned to 1 of 5 test diets or the basal diet for a total of 4 replications per diet per group. Two groups of gilts were used for each set of coproducts, resulting in 8 replications per coproduct and 32 replications of the basal diet. The experiment was conducted as a completely randomized design. Gilts were placed in metabolism crates and offered 3 kg daily of their assigned test diet for 13 d, with total collection of feces and urine during the last 4 d. Ingredients were analyzed for DM, GE, CP, ether extract, crude fiber, NDF, ADF, total dietary fiber (TDF), ash, AA, and minerals, and in vitro OM digestibility was calculated for each ingredient. The GE was determined in the diets, feces, and urine to calculate DE and ME for each ingredient. The DE and ME of the basal diet were used as covariates among groups of pigs. The DE of the coproducts ranged from 2,517 kcal/kg of DM (corn gluten feed) to 8,988 kcal/kg of DM (corn oil), and ME ranged from 2,334 kcal/kg of DM (corn gluten feed) to 8,755 kcal/kg of DM (corn oil). By excluding corn oil and corn starch from the stepwise regression analysis, a series of DE and ME prediction equations were generated. The best fit equations were as follows: DE, kcal/kg of DM = -7,471 + (1.94 × GE) - (50.91 × ether extract) + (15.20 × total starch) + (18.04 × OM digestibility), with R(2) = 0.90, SE = 227, and P < 0.01; ME, kcal/kg of DM = (0.90 × GE) - (29.95 × TDF), with R(2) = 0.72, SE = 323, and P < 0.01. Additional equations for DE and ME included NDF in the instance that TDF data were not available. These results indicate that DE and ME varied substantially among corn coproducts and that various nutritional components can be used to accurately predict DE and ME in corn coproducts for finishing pigs.

RESEARCH: Industrial evaluation of a dynamic controller for simultaneous saccharification and fermentation process

Abstract The dry grind corn industry is the largest ethanol producer in the US. Simultaneous saccharification and fermentation (SSF) is one of the most critical process steps that determines the ethanol yields and conversion efficiency of the whole process. Due to its complexity, the SSF process is not completely controlled in dry grind corn processing plants. Previously, a dynamic optimal controller to control of the fermentation process was developed and demonstrated on a 15 L laboratory-scale system. The dynamic controller (DC) was used to determine fermentor temperature, pH and amount of glucoamylase to achieve optimum performance. Validation of this optimal controller was conducted in a commercial dry grind ethanol plant. During commercial trial, DC maintained average peak glucose concentration of 3.15 ± 0.58 (% w/v) for the SSF process compared to 7.9 ± 0.36 (% w/v) for conventional SSF process (no DC). There was no difference (p value = 0.077 for a two tailed, unequal variance, unpaired students t-...

Changes in Lipid Composition During Dry Grind Ethanol Processing of Corn

AbstractDuring the dry grind ethanol process, ground corn is fermented and the major co‐product is a feed called distillers dried grains with solubles (DDGS). This study investigated the changes that occur in the composition of corn oil that can be extracted from various process fractions during the dry grind ethanol process. In the first part of this study, samples of distillers dried grains, thin stillage, condensed distillers solubles (also known as syrup), and DDGS were obtained from 7 dry grind ethanol plants. The levels of deleterious free fatty acids were high (&gt;7%) and those of valuable total phytosterols were also high in all fractions (&gt;2%). In the second part of this study, changes in the content and composition of the fatty acids, phytosterols, tocopherols and tocotrienols were quantitatively analyzed in crude oil samples extracted from nine dry grind process fractions from three commercial ethanol plants. Fatty acid and phytosterol composition remained nearly constant in all nine fractions, although some significant variations in phytosterol composition existed among the fractions. Examination of the tocopherols and tocotrienols revealed that γ‐tocopherol was the most abundant tocol in ground corn but an unknown tocol became the predominant tocol after fermentation and persisted in the remaining processing fractions and in the final DDGS product. Overall, the remaining majority of tocols remained relatively unchanged.

Anaerobic digestion of whole stillage from dry-grind corn ethanol plant under mesophilic and thermophilic conditions

Anaerobic digestion of whole stillage from a dry-grind corn-based ethanol plant was evaluated by batch and continuous-flow digesters under thermophilic and mesophilic conditions. At whole corn stillage concentrations of 6348 to 50,786 mg total chemical oxygen demand (TCOD)/L, at standard temperature (0 °C) and pressure (1 atm), preliminary biochemical methane potential assays produced 88±8 L (49±5 L CH4) and 96±19 L (65±14 L CH4) biogas per L stillage from mesophilic and thermophilic digesters, respectively. Continuous-flow studies for the full-strength stillage (TCOD=254 g/L) at organic loadings of 4.25, 6.30 and 9.05 g TCOD/L days indicated unstable performance for the thermophilic digester. Among the sludge retention times (SRTs) of 60, 45 and 30 days tested, the mesophilic digestion was successful only at 60 days-SRT which does not represent a practical operation time for a large scale bioethanol plant. Future laboratory studies will focus on different reactor configurations to reduce the SRT needed in the digesters.

Effect of compositional variability of distillers’ grains on cellulosic ethanol production

In a dry grind ethanol plant, approximately 0.84 kg of dried distillers’ grains with solubles (DDGS) is produced per liter of ethanol. The distillers’ grains contain the unhydrolyzed and unprocessed cellulosic fraction of corn kernels, which could be further converted to ethanol or other valuable bioproducts by applying cellulose conversion technology. Its compositional variability is one of the factors that could affect the overall process design and economics. In this study, we present compositional variability of distillers’ grains collected from four different dry grind ethanol plants and its effect on enzymatic digestibility and fermentability. We then selected two sources of distillers grains based on their distinctive compositional difference. These were pretreated by either controlled pH liquid hot water (LHW) or ammonia fiber expansion (AFEX) and subjected to enzymatic hydrolysis and fermentation. Fermentation of the pretreated distillers’ grains using either industrial yeast or genetically engineered glucose and xylose co-fermenting yeast, yielded 70–80% of theoretical maximum ethanol concentration, which varied depending on the batch of distillers’ grains used. Results show that cellulose conversion and ethanol fermentation yields are affected by the compositions of distillers’ grains. Distillers’ grains with a high extractives content exhibit a lower enzymatic digestibility but a higher fermentability.

An engineering and economic evaluation of quick germ–quick fiber process for dry-grind ethanol facilities: Analysis

An engineering economic model, which is mass balanced and compositionally driven, was developed to compare the conventional corn dry-grind process and the pre-fractionation process called quick germ–quick fiber (QQ). In this model, documented in a companion article, the distillers dried grains with solubles (DDGS) price was linked with its protein and fiber content as well as with the long-term average relationship with the corn price. The detailed economic analysis showed that the QQ plant retrofitted from conventional dry-grind ethanol plant reduces the manufacturing cost of ethanol by 13.5 ¢/gallon and has net present value of nearly $4 million greater than the conventional dry-grind plant at an interest rate of 4% in 15 years. Ethanol and feedstock price sensitivity analysis showed that the QQ plant gains more profits when ethanol price increases than conventional dry-grind ethanol plant. An optimistic analysis of the QQ process suggests that the greater value of the modified DDGS would provide greater resistance to fluctuations in corn price for QQ facilities. This model can be used to provide decision support for ethanol producers.