Grain and Chaff
When both are wanted from wheat and barley it will no longer make sense to thresh in the fields. Instead, intact heads of the plants will be gathered.
Cereal chaffs are created in the process of threshing wheat, barley and similar small grains. Threshing breaks up the grain head (spike) and separates the grain from the rest, which chaff consists of small bits. At present, this occurs in the fields using a combine harvester, the chaff being blown out the back of the combine.
Those few farmers who now bother to gather chaff often use a small cart pulled behind the combine into which chaff is blown and accumulates. Periodically its load is dumped on the ground by tilting the cart’s bed sharply while raising the tailgate out of the way. …The small pile of chaff simply slides onto the field. ..The bed is raised, the tailgate comes down, and a new pile begins to form. ..Small piles of chaff then dot the field to be later gathered and taken to the farmyard.
This is an awkward, make~do, harvesting of chaff which is applied to only a few fields, since the harvest generates much more chaff than can be used by most farmers. ..But were the chaff processed on farm and made into a marketable product, then all the chaff would be wanted, and threshing wheat or barley in the field would end, as a cheaper way of harvesting would be used instead.
New Harvest
A header — a modified windrower (swather) –would cut the crop a little below the grain heads and throw these back into an accumulator of some sort, which might form a bale, or small stack, or compact high windrow to be left in the field to dry down. The bale may be a loose type made by a pendulum style baler used for hay. ..Or these heads could be thrown into truck box or wagon and hauled directly to the farmyard.
Because wheat and barley are bearded and the straw with the heads is short, the long awns will interlock and little compression should be required to form a coherent form that won’t fall apart, be they smallish formed shapes or short stacks. ..When taken to the farmyard, larger piles may be made that air will naturally go through. Air that has picked up moisture will be heavier and fall out of the pile, to be replaced with drier surrounding air. ..Any wind blowing on the pile naturally aids this process..Only in very rainy falls might assisted drying be needed, a matter of blowing air through the stacks.
Threshing would then come later, perhaps weeks later, when the heads would be very dry. This means separation of chaff from threshed grain could be simply by use of a cyclone, the grain dropping down, the chaff swirling around and out. ..A machine of smallish capacity could be employed, run by electricity if that be cheaper. _Alternatively, a custom thresher could come and do it all in a few days. Either way the chaff would be saved, for it would be valuable.
About chaff
Chaff is low density and not of much benefit for ruminants, the animals getting less from it than the effort involved in its digestion. ..Despite being mainly composed of sugar polymers, it has low value as a feedstuff.
Like many other cellulosics, chaff has three main components, each a polymer: ..the stiffest and largest is cellulose, a long chain of glucose units that is tightly packed and folded in on itself repeatedly making it difficult for enzymes to access. ..Closely associated with it is the xylan polymer, which can be said to shield the cellulose. It is a chain mainly of xylose units, but branched and thus readily attacked.
Lignin coats the other two and is a disorderly polymer of units that are not digestible and have no feed value. ..It blocks easy access to the cellulose polymer in particular. ..In consequence, it takes time for enzymes to attack chaff and take apart the useful polymers, starting with the more readily dismembered xylan which then exposes more of the difficult to dismember cellulose.
{{ Alternatively, much of the lignin can first be removed, leaving the resultant material more digestible in the rumen… or fermenter. }}
While appropriate enzymes will break down the xylan polymer, it is more efficient to remove it chemically. This creates pathways for the enzymes that attack cellulose to have easier access to it, despite the lignin, which gives the treated chaff a higher feed value.
In an industrial ferment, given enough time and the appropriate enzymes, the cellulose will be largely digested. ..However, if the xylan is not largely removed, this is a slow process, so there is a time factor. The shorter the period needed to digest the cellulose, the more material will cycle through the fermenter.
Similarly, treated chaff is more digestible in the rumen and therefore an energy feed for ruminant animals– not a particularly good one, but a cheap one. The enzymes there are created in situ by the mix of microbes in the rumen. A similar mix of microbes may be used in the industrial fermenter, so enzymes as such will not need to be supplied.
Chaff Product
Likely what would be most marketable is a flowable relatively dense product or products. Three sorts of large volume buyers potentially exist, being: (1) cattle feeders, especially as part of finishing rations; (2) fermentors, particularly of biofuels; and (3) furfural makers. …Each has different needs.
Cattle feeders would want treated chaff such that the cellulose content could be digested easily by cattle, as it represents a less expensive substitute for grain, particularly barley, in the ration.
Furfural makers, however, would want a product high in xylan (or xylose) as only it gets turned into furfural, cellulose being of no use to them for that purpose.
However, they can couple this with a cellulose ferment. Some microbes have a strong preference for six~carbon (6C) sugars such as glucose, over five~carbon (5C) xylose. ..Thus they can ferment the cellulose even with xylan present, then stop the ferment and use the shunned xylan to make furfural.
As for fermentors, some will prefer one of the above, others the other. It depends on what microbes are being used, on what products are being produced, and on how these are isolated from the ferment. {See also the page: _ A Ketone Biogasoline.}
So, two products then: ..one chaff with xylan largely removed, and another chaff high in xylan or xylose. ..Removing much of the xylan from some chaff and adding that to untreated chaff would create the basis for making these two products.
Two usual means of removing xylan are acid treatment and alkali treatment. Acid provides xylose mainly, while an alkali such as NaOH or KOH producers short chains of xylans from the native polymer. ..It will also split acetyls off the xylan to yield the acetate salt. ..Acid treatment instead gives acetic acid from these acetyls.
For several reasons alkali treatment seems best. It is an exothermic reaction. The hot solution obtained may be absorbed on fresh chaff and then dried somewhat before being compacted. This forces the solution into the fresh chaff whereupon unreacted alkali will then attack the xylan in that fresh material. Short xylan chains, or oligoxylan, has adhesive properties that hold compacted material together. So it takes less force to form a hard dense pellet.
As to how to effect such an alkali treatment, no doubt several ways will come to exist. ..There are literally hundreds of research papers describing how alkali treatments of various materials have been carried out. ..Time, temperature, strength of the alkali solution, and ratio of it to the dry matter content of the material are all variables to consider. ..A weak solution applied, held some while, squeezed out and perhaps repeated might be best, considering the processing steps that follow.
Meanwhile, the extracted chaff will be wet and have a small amount of alkali present, likely not enough to be a problem when fed cattle. ..In formulating their ration an acidic material, a little silage say, would neutralise any alkali and thus prevent mouth burn that the alkali itself might induce. ..Alternatively, CO2 will neutralise the alkali by forming its bicarbonate salt.
The extracted wet chaff could be dried and compacted, perhaps mixed with dry chaff before doing so in order to reduce the amount of drying required. Or, of course, it could be delivered wet to a nearby feedlot.
In summary, two marketable compact chaff products could be made on farm and induce a farmer to collect chaff as well as grain from wheat and barley fields in particular. ..Doing so would change the equipment used for harvest, replacing the combine harvester. ..This would reduce harvesting expense while increasing income by sale of the compacted chaff products.
Before the Combine
The combine harvester is a large overly expensive machine used but a few weeks a year. It is called a combine because it both reaps and threshes, tasks that before were separate.
A machine called a binder cut the crop near the ground, gather it in bunches, tied same with twine, then drop these sheaves (as they were called) on the ground. A man on foot put several together firmly placing the butts on the ground while leaning the tops against each other. When done right these stooks (as they were called) shed any rain and resisted wind. They were then left many days to dry down.
Obviously, the binder needed little power. The oldest ones were pulled by three or four horses (or two if the width of cut was small), the mechanism powered from one wheel. When a tractor became used, it was a small one.
Once the stooks had dried, men with pitchforks threw them on a flat bed wagon to be taken to a stationary threshing machine that sent grain into a smaller wagon with sides. Chaff and straw were each blown into separate piles, and at harvest’s end the chaff pile was usually burnt. So would be any surplus straw, though much of it would be taken to the farmyard to be used as bedding for livestock. That harvest was labour intensive.