Carl A. Westby

Cofermentation of sweet sorghum juice and grain for production of fuel ethanol and distillers' wet grain

Abstract In an attempt to reduce the costs associated with fuel ethanol production from grain, the authors used sweet sorghum juice as a partial or complete replacement for tap-water in mash preparation and fermentation. This juice, which was an unutilized by-product of sweet sorghum silage preservation by the Ag-Bag method, contained 6·5–7·6% (wt/wt) reducing sugar and produced up to 3·51% (v/v) ethanol beers after fermentation. Varying amounts of this juice were mixed with water and corn or wheat, either before or after liquefaction (front-end or back-end loading, respectively). When over 60% juice replacement was used in front-end loading trials, salt buildup, due to required pH adjustments during cooking, inhibited yeast metabolism and thereby reduced yields. This inhibition was not observed during back-end loading trials since acid and base usage during cooking were reduced. However, in all trials we noted yeast inhibition by some factor(s) present in juice from sweet sorghum variety NK 8368. This inhibition was not observed with variety NK 405. If sweet sorghum juice is used to replace 40% of the water and either 12·5% of the corn or 12% of the wheat in mash preparation, production costs can be reduced by

Use of potassium meta bisulfite to control bacterial contaminants during fermentation of fodder beet cubes for fuel ethanol

0.032/liter (

Solid phase fermentation of foder beets for ethanol production: Effect of grind size

0.12/US gallon) for corn and

Effect of pulp pH on solid phase fermentation of fodder beets for fuel ethanol production

0.040/liter (

Processing cereal grains, thin stillage, and cheese whey to fuel ethanol in a farm-scale plant

0.15/US gallon) for wheat.

Preventing contamination during diffusion fermentation of fodder beet cubes by pH control

Abstract Potassium meta bisulfite (PMB) was used to control bacterial contamination during batch (BDF) and sequential batch diffusion fermentation (SBDF) of fodder beets. For BDF, equal amounts of beet cubes (1·27–1·91 cm) and water were mixed with a yeast inoculum and 0–0·4% (wt/wt) PMB. At a PMB concentration of 0·25%, contamination was prevented and the ethanol yield (85% of theoretical; 4·55%, v/v) and fermentation efficiency (96%) were highest. In the SBDF process, five batches of fresh beet cubes were sequentially fermented to ethanol in the same yeast-liquid mixture. Makeup series of 0, 50, 75 and 100% were run. In the 75% (0·25% PMB in batch 1 and 0·188% in batches 2–5) and 100% (0·25% PMB throughout) series, contamination was checked or prevented while ethanol concentrations of 8·6–8·85% (v/v) were attained by the fifth batch. BDF and SBDF simulated start-up and operating conditions, respectively, in a pilot-scale, continuous diffusion fermentor which the authors are developing for commercial production of ethanol from fodder beets.

Intermediate-Scale, Semicontinuous Solid-Phase Fermentation Process for Production of Fuel Ethanol from Sweet Sorghum

Abstract Solid phase fermentation of pulped fodder beets was studied to see what effect beet particle size had on various fermentation parameters. All trials were run in 4-l stainless stell containers and hammermilled pulp was initially adjusted to pH 3.0 to control bacterial contaminants. The maximum yeast population that built up in the pulp was independent of the hammermill screen size (0.476–1.905 cm) and averaged 2.0−2.3 × 108 cells/ml. Pulp from finer screens (0.476–0.953 cm) took 19–22 h to reach a peak yeast population while pulp from coarser screens (1.270–1.905 cm) took a slightly longer 24–28 h. The time to reach maxium ethanol concentration was not affected by screeen size and averaged 28–30 h. Ethanol yields dropped slightly form 85–87% of theoretical with the finest screens to 83–84% with the coarset screens. The maximum ethanol concentration observed was 7.96% (v/v) and the average of all runs was 7.63% (v/v). Fermentation efficiency averaged 98–99% thoughout. The lack of a response to grinding fodder beets with different screens was due to their wet fibrous nature which hindered free flow of pulp though the screens. Pulp was, instead, extruded though the screens, forming particles of generally similar size. Our results indicate that the primary consideration for grind size is energy consumption for grinding. Therefore, if a hammermill is used, a large screen (1.270–1.905 cm) which requires less energy should be employed so as to minimize energy consumption. This strategy does not result in longer fermentation times or reduced ethanol yields.

A continuous, farm‐scale, solid‐phase fermentation process for fuel ethanol and protein feed production from fodder beets

SummaryThe pH of fodder beet pulp was varied to see how this affected solid phase fermentation by yeast. The process is for fuel ethanol production. When pulp was adjusted to a pre-inoculation pH of 3.0–3.5, ethanol yields (78–85% of theoretical, averaging 8.9% v/v) and fermentation efficiencies (97–99%) were greatest, the fermentation time was the shortest (30–39 h) and no bacterial contamination occurred.

Farm-scale production of fuel ethanol and wet grain from corn in a batch process

Hydrous fuel ethanol (95%) and distillers wet grain (DWG) were produced in a farm-scale plant (< 4 million liters ethanol year−1) from corn, wheat, and grain sorghum particles of various sizes, from corn combined with thin stillage-whey, and from various other cereal grains. These variations were made in a search to find the best set of conditions for maximizing the energy balance (energy output divided by energy input) and minimizing the cost of ethanol production. We found that the optimum hammermill screen size for corn, wheat, and grain sorghum was 1·59–2·38 mm. In tests with thin stillage and whey a higher energy balance (2·91) occurred when one part whey was mixed with three parts stillage, rather than the reverse (2·69). However, the reverse (three parts whey and one part stillage) gave a lower ethanol cost (

Effects of Inoculum Size on Solid-Phase Fermentation of Fodder Beets for Fuel Ethanol Production

0.45 liter−1) than the original (