G. T. Schelling

Removal and utilization of ethanol stillage constituents

Abstract A farm-scale ethyl alcohol plant was used to produce whole stillage from ethanol production using corn and grain sorghum as feedstocks. The stillage was separated into wet pressed solids and thin stillage liquids fractions using a commercial dewatering screw press. Thin stillage liquids from several batches were processed further by centrifugation. Results indicated that nitrogen (or crude protein) concentration was increased by 240% (dry basis) in wet solids fed to cattle and 100% (d.b.) in thin stillage liquids. Biochemical oxygen demand averaged 28 500 ppm and suspended solids concentration ranged from 12 000 to 35 000 ppm. Most of the nitrogen, starch, and crude fiber were contained in stillage dry matter. Centrifugation removed 40% of suspended volatile solids and reduced chemical oxygen demand by 25%. Nearly all the sugar and ash content of whole stillage was in dissolved form and remained with the waste-water after dewatering and centrifugation. The wet pressed solids fraction was highly palatable to cattle but spoiled rapidly. Fermentation of corn and grain sorghum for ethanol production improved the amino acid content and protein quality of fermentation products. The dry matter digestibility of the wet pressed solids fraction from grain sorghum stillage was determined from cattle feeding trials to be 76.9%.

Grain sorghum stillage processing: nutrient recovery and pollution control.

ABSTRACT STILLAGE from fuel alcohol plants contains reusable nutrients and water polutants. Grain sorghum stillage from a farm-scale fuel alcohol plant was separated into wet solids and liquid fractions by various processes. Dry matter recovery averaged 42% with a screw press, 21 and 34% with two centrifuges, 98% with a reverse osmosis unit, and 19% with ultrafiltration. More than 99% of the nitrogen (protein) was recovered with three stages of treatment. Resulting wastewater still had a chemical oxygen demand of 4100-9400 ppm and would require biological treatment or land application.

Modes of Action in Manipulating Rumen Function

The ionophore monensin is used as a model to examine the nodes of action that are important in manipulating rumen function. It appears likely that several system modes of action come into play and that they result from the basic mole of action of the ionophore which involves the modification of the movement of ions across the biological membranes of rumen microbes. While there are a number of biological claims reported in the literature for monensin, they can be consolidated to seven categories or system modes of action. The modification of acid production is one well recognized category of great importance. Modified feed intake should also be considered to be important. The third system mode of action, change in gas production, probably only contributes a limited savings in energy. Modified digestibilities are probably quite variable as a mode of action, but would appear to be a significant factor. The change in protein utilization appears to result from several factors that are probably occuring simultaneously. Modification of rumen fill and rate of passage may play an important role in causing some of the previously mentioned system modes of action to occur, but this is not presently clear. A seventh category inclusive of several nonensin responses that are more indirect to the rumen or sporadic in nature is included. It appears that monensin responses occur as a result of these several system modes of action which probably act in concert. It is impossible to accurately assess a quantitative contribution of each of these categories at the present time.