Virgil R. Bremer

Improvements in Life Cycle Energy Efficiency and Greenhouse Gas Emissions of Corn‐Ethanol

Corn-ethanol production is expanding rapidly with the adoption of improved technologies to increase energy efficiency and profitability in crop production, ethanol conversion, and coproduct use. Life cycle assessment can evaluate the impact of these changes on environmental performance metrics. To this end, we analyzed the life cycles of corn-ethanol systems accounting for the majority of U.S. capacity to estimate greenhouse gas (GHG) emissions and energy efficiencies on the basis of updated values for crop management and yields, biorefinery operation, and coproduct utilization. Direct-effect GHG emissions were estimated to be equivalent to a 48% to 59% reduction compared to gasoline, a twofold to threefold greater reduction than reported in previous studies. Ethanol-to-petroleum output/input ratios ranged from 10:1 to 13:1 but could be increased to 19:1 if farmers adopted high-yield progressive crop and soil management practices. An advanced closed-loop biorefinery with anaerobic digestion reduced GHG emissions by 67% and increased the net energy ratio to 2.2, from 1.5 to 1.8 for the most common systems. Such improved technologies have the potential to move corn-ethanol closer to the hypothetical performance of cellulosic biofuels. Likewise, the larger GHG reductions estimated in this study allow a greater buffer for inclusion of indirect-effect land-use change emissions while still meeting regulatory GHG reduction targets. These results suggest that corn-ethanol systems have substantially greater potential to mitigate GHG emissions and reduce dependence on imported petroleum for transportation fuels than reported previously.

Evaluation of Dry Distillers Grains Plus Solubles Inclusion on Performance and Economics of Finishing Beef Steers1

A 167-d feedlot study was conducted to evaluate feeding increasing levels of dry distillers grains plus solubles (DDGS) to finishing cattle and the impact on performance and profitability. Crossbred steer calves (n = 240, BW = 306 ± 24.5 kg) were used in 30 pens with dietary treatments of 0, 10, 20, 30, and 40% DDGS dietary inclusion (DM basis). Quadratic relationships (P 0.15) by DDGS level, but G:F tended to be quadratic (P = 0.10) as 20% DM inclusion had the greatest value, although steers fed all levels of DDGS had numerically greater G:F compared with steers fed no DDGS. Carcass characteristics, other than hot carcass weight, were not affected by DDGS treatment. Energy value of DDGS at 10 to 40% dietary inclusion resulted in a quadratic trend (P = 0.10) and remained above corn, with the highest values at 10 and 20% inclusion averaging 127% of corn. When DDGS was priced equally to corn, all levels of DDGS from 10 to 40% inclusion resulted in higher profits compared with a dry-rolled corn based diet regardless of corn price. The greatest returns were observed when cattle were fed 20% DDGS. These data indicate that DDGS can be fed up to 40% DM to improve cattle performance and result in economic profits, with optimum levels at 20 to 30% diet DM.

Nutrient variability for distillers grains plus solubles and dry matter determination of ethanol by-products1

ABSTRACT Three experiments were conducted to evaluate nutrient content and DM determination methods of dry milling byproducts. In Exp. 1, nutrient composition was determined for wet distillers grains plus solubles (WDGS) and modified distillers grains plus solubles (MDGS) from 6 ethanol plants with 10 samples collected per day, across 5 d, and sampling was repeated over 4 separate months. Mean composition was 31.0% CP, 11.9% fat, 0.84% P, and 0.77% S (DM basis). Coefficients of variation for DM content were greater for some plants than others, and variation occurred within and across days. Variability was small for CP and P, whereas fat differed among ethanol plants. Large variation in means and CV were observed for S in period 1, but variation subsequently decreased. Coefficients of variation for S were similar for samples collected within the same day and across days. In Exp. 2, samples of WDGS, MDGS, Dakota Bran Cake, and distillers solubles were used to determine DM content by drying samples at 105°C for 3, 8, and 24 h and 60°C for 24 and 48 h, vacuum oven drying, toluene distillation, and Karl Fischer titration. Compared with toluene distillation, drying at 105°C resulted in less DM (P ≤ 0.10) and vacuum drying and Karl Fischer titration resulted in greater DM (P

Emissions savings in the corn-ethanol life cycle from feeding coproducts to livestock.

Environmental regulations on greenhouse gas (GHG) emissions from corn (Zea mays L.)-ethanol production require accurate assessment methods to determine emissions savings from coproducts that are fed to livestock. We investigated current use of coproducts in livestock diets and estimated the magnitude and variability in the GHG emissions credit for coproducts in the corn-ethanol life cycle. The coproduct GHG emissions credit varied by more than twofold, from 11.5 to 28.3 g CO(2)e per MJ of ethanol produced, depending on the fraction of coproducts used without drying, the proportion of coproduct used to feed beef cattle (Bos taurus) vs. dairy or swine (Sus scrofa), and the location of corn production. Regional variability in the GHG intensity of crop production and future livestock feeding trends will determine the magnitude of the coproduct GHG offset against GHG emissions elsewhere in the corn-ethanol life cycle. Expansion of annual U.S. corn-ethanol production to 57 billion liters by 2015, as mandated in current federal law, will require feeding of coproduct at inclusion levels near the biological limit to the entire U.S. feedlot cattle, dairy, and swine herds. Under this future scenario, the coproduct GHG offset will decrease by 8% from current levels due to expanded use by dairy and swine, which are less efficient in use of coproduct than beef feedlot cattle. Because the coproduct GHG credit represents 19 to 38% of total life cycle GHG emissions, accurate estimation of the coproduct credit is important for determining the net impact of corn-ethanol production on atmospheric warming and whether corn-ethanol producers meet state- and national-level GHG emissions regulations.

Effect of distillers grains moisture and inclusion level in livestock diets on greenhouse gas emissions in the corn-ethanol-livestock life cycle1

A model was previously developed (Biofuel Energy Systems Simulator; https://www.bess.unl.edu) to predict greenhouse gas (GHG) emissions and net energy yield when ethanol is produced from corn. The model also predicts feedlot cattle, dairy cattle, and swine performance and feed replacement value of ethanol coproducts. Updated equations that predict performance of feedlot cattle fed 0 to 40% of dietary DM as corn wet (WDGS), modified (MDGS), or dry (DDGS) distillers grains plus solubles replacing dry-rolled and high-moisture corn were developed and incorporated into the model. Equations were derived from pen-level performance for 20 finishing studies evaluating WDGS, 4 evaluating MDGS, and 4 evaluating DDGS conducted at the University of Nebraska. Feeding value of WDGS was 145 to 131% of corn replaced when included at 20 to 40% of diet DM due to a quadratic (P < 0.01) increase in G:F. The feeding value of MDGS was 124 to 117% with a quadratic (P < 0.01) increase in G:F and 112 to 110% for DDGS with a linear (P < 0.01) increase in G:F. Midwest corn-ethanol-livestock life cycle GHG reduction relative to gasoline (97.7 g CO2 equivalent/MJ of ethanol) was 61 to 57% when WDGS was fed to feedlot cattle for 20 to 40% diet inclusion. Feeding MDGS and DDGS to feedlot cattle reduced GHG emissions from the corn-ethanol-cattle system by 53 to 50% and 46 to 41%, respectively. Feeding WDGS to feed-lot cattle was the optimum feed use of distillers grains plus solubles based on feeding performance and GHG reduction.

A meta-analysis evaluation of supplementing dried distillers grains plus solubles to cattle consuming forage-based diets 1

Data from 20 (13 pasture grazing and 7 confinement-fed) forage-based growing studies utilizing 790 steers and heifers supplemented dried distillers grains (DDGS) were analyzed using mixed models to determine the response to supplementing different levels of DDGS on gain and forage intake. Thirty-eight treatment means (442 cattle) were from grazing cattle supplemented DDGS (range: 0.00 to 1.03% BW/d). Twentyeight treatment means (348 cattle) were from confinement-fed cattle supplemented DDGS (range: 0.00 to 1.27% BW/d). Outcomes of interest were the effect of DDGS intake on forage intake (confinement studies), final BW, and ADG. In pasture grazing studies, final BW increased linearly (P < 0.01) and tended to increase quadratically (P = 0.07) with increasing DDGS supplementation. Daily gain increased linearly (P < 0.01) with increased DDGS supplementation. Results from confinement-fed studies indicate that final BW (P < 0.01) and ADG (P < 0.01) increased quadratically with increasing DDGS supplementation. Intakes measured in the confinement studies suggest that increasing DDGS supplementation increases total DMI (P < 0.01) quadratically, even though forage intake decreases (P < 0.01) quadratically with increased DDGS supplementation. Results from all studies indicate that increasing DDGS supplementation increases ADG and final BW, and supplementation of DDGS replaces some forage in forage-based diets fed to growing cattle.

Effect of sulfur content in wet or dry distillers grains fed at several inclusions on cattle growth performance, ruminal parameters, and hydrogen sulfide

Effects of S from wet or dry distillers grains with solubles (DGS) containing 0.82 or 1.16% S on animal growth performance, carcass characteristics, apparent total tract digestibility, and ruminal parameters were evaluated. In Exp. 1, crossbred beef steers (n = 120; 345 ± 34 kg BW) were individually fed ad libitum using Calan gates. Treatments were applied as a 2 × 2 × 3 + 1 factorial treatment arrangement with factors of DGS type (wet or dry), S content in DGS (0.82 or 1.16% DM basis), and DGS inclusion (20, 30, and 40%, DM basis), as well as a corn control diet (no DGS). In Exp. 2, ruminally cannulated crossbred beef steers (n = 6; 381 ± 31 kg BW) were assigned to 1 of 5 diets in a 5 × 6 unbalanced Latin Square design and fed ad libitum through five 14-d periods. A 2 × 2 + 1 factorial treatment arrangement was used with the factors of DGS type and S content in DGS (similar to Exp. 1). Inclusion of DGS was 40%, except for a MATCH diet containing wet 1.16% S DGS included at 31.4% (DM basis). Intake of DM decreased linearly (P < 0.01) and quadratically (P < 0.01) for steers fed wet and dry DGS that was 1.16% S, respectively. In addition, steers fed dry DGS consumed 9% more DM (P < 0.01) than those fed wet. Gain decreased linearly (P = 0.02) when wet 1.16% S DGS increased in the diet, representing a 12% drop in ADG between the Control and 40% DGS inclusion. A quadratic (P = 0.02) improvement in G:F was observed for steers fed wet DGS compared with dry, regardless of S content (P = 0.52). Feeding diets with wet 1.16% S DGS linearly decreased (P = 0.03) HCW. In Exp. 2, molar proportion of propionate declined (P = 0.01) 9% and A:P ratio tended (P = 0.13) to be greater when 1.16 compared with 0.82% S DGS was fed. Apparent total tract DMD was not affected (P > 0.16) and only subtle changes (P < 0.01) in ruminal pH parameters were observed. Greater (P = 0.02) ruminal H2S concentration for steers fed wet compared with dry DGS was observed, while 1.16% S DGS tended (P = 0.12) to produce greater ruminal H2S than 0.82% S. Sulfur in wet DGS appears to be more prone to be converted to ruminal H2S, because feeding 1.16% S as wet DGS had a greater impact on ADG, DMI, and ruminal H2S compared with dry DGS.

Evaluation of a prefermentation-fractionated by-product corn grain dry milling ethanol process in growing and finishing cattle diets1

ABSTRACT Two experiments were conducted to evaluate feeding a new by-product feed containing bran and solubles from a prefermentation-fractionated dry milling process, Dakota Bran (DBRAN), and compare this to feeding dry distillers grains plus solubles (DDGS). In the growing experiment, 256 crossbred steer-calves (BW = 281 ± 23.2 kg) were fed 4 diets designed as a 2 × 2 factorial with factors of level (15 or 30%) and type (dried and pelleted DBRAN or DDGS fed as a meal) in which by-products replaced a 70:30 blend (DM basis) of bromegrass hay and alfalfa haylage. No significant interactions (P ≥ 0.33) were observed for cattle performance between by-product level and type. Ending BW, ADG, DMI, and G:F increased (P

Software Tool for Integrating Feed Management into Nutrient Planning

The introduction of ASABE Standard D384.2, Manure Production and Characteristics, has created the opportunity to integrate feed management decisions and animal performance measures into nutrient planning processes. This paper introduces a software tool that integrates estimates of nutrient excretion based on the new standard with estimates of land need, labor and equipment time allocation, and economic cost and benefit for manure application. This tool will be used to evaluate the economic implications for two scenarios using beef cattle examples as a means of illustrating tool application. The first scenario will look at the impact of feeding ethanol co-products on the economics of manure application. Labor and equipment time requirements, land access needs and economic cost all increase significantly with greater inclusion rates of co-product in the diet. However, the value of the additional nutrients is potentially greater than economic cost. The second scenario explores the impact of alternative methods for determining application rate (nitrogen vs. phosphorus based application rate). For the situation evaluated, the increase in land needs was substantial but the increased time and economic costs were modest when transitioning from an N-based to a four year P-based rate. However, applying manure to supply a single year P-based rate substantially increased the equipment and labor requirements as well as the overall manure application costs.