Philippe Savoie,[3]1 Kevin J. Shinners,2
and Benjamin N. Binversie2

1Agribulture and Agri-Food Canada, 2560 Hochelaga Boulevard,
Sainte-Foy, Qubbec, Canada G1V 2J3, E-mail: psavoie@grr. ulaval. ca; and
2Biological Systems Engineering Department,

University of Wisconsin, 460 Henry Mall, Madison, WI 53706

Abstract

Mixing fresh silage in water resulted in partial segregation of grain from stover. Grain concentration was 75% in the sunk material when silage was relatively dry (64% moisture content [MC]) and 41% when silage was rela­tively wet (74% MC). Partial drying to remove 20 percentage units of mois­ture prior to water separation increased grain concentration to 92%, and complete drying increased grain concentration to 99%. Sieving without dry­ing followed by water separation resulted in a grain concentration of 79%. A byproduct of water separation is a large amount of soluble and deposited fine particles in the effluent: 18% of original dry matter after one separation, and between 21 and 26% after eight separations. In an industrial setting, hydrodynamic separation of silage with minimal pretreatment could pro­vide a feedstock with a high concentration of grain (75-80%). In a laboratory setting, hydrodynamic separation with prior oven drying could provide a method to separate grain from stover in corn silage by reaching a grain con­centration higher than 99%.

Index Entries: Corn; stover; grain; separation; silage.

Introduction

Various methods for separating corn grain from stover have been proposed. One approach is to shell the grain with a combine and subse­quently to harvest the residual stover with either a forage harvester or a baler (1). Another approach is to harvest, chop, and ensile the whole crop, and to separate components at removal from storage (2). Advantages of separation after storage include fast and efficient harvest in a single stream;

low-cost storage in high-capacity bunker silos without the need for grain drying; and separation throughout the year at relatively low work rates, with small size equipment, compared with the high rates handled during the short harvest season.

After ensiling, grain has been sorted from stover, at least partially, by mechanical sieving (3) or aerodynamic separation (4). Hydrodynamic sepa­ration has not previously been used for corn silage, but it is used industri­ally to separate heavier particles such as phosphatides from corn oil in the wet-milling process (5).

Hydrodynamic separation of grain from stover could be feasible if components exhibit significant differences in specific gravity or buoyancy. The specific gravity of corn grain has been observed to range from 1278 to 1380 kg/m3 (6). The specific gravity of corn stover components (stalk, cob, leaf, husk) is less well documented. Meanwhile, the specific gravity of for­age particles is in the order of 1500 kg/m3 (7). This would suggest poor hydrodynamic separation of grain from stover in water because both com­ponents would sink. However, empirical evidence shows that grain sinks more rapidly than stover, which tends to float because of buoyancy.

The objective of the present work was to evaluate the potential of hydrodynamic separation with water to sort grain from stover after ensiling. New data are presented on the specific gravity of corn grain and stover components after coarse chopping or grinding. Factors considered include harvest conditions (chop length and processing) and pretreatment of the silage (partial drying, sieving) prior to hydrodynamic separation.