A Cheaper Maize Harvest
Herein, by cobcorn is meant an ear of maize sans its enveloping wrap of leaves, a naked ear. ..It is comprised of these major components — starch.., xylans .., cellulose.., and lignin. ..All the starch is in the kernels of grain, as the cob or core to which the kernels are attached has none.
Somewhat over 70% of the dry matter of the kernels is starch, which amounts to ~60% of the dry matter of a cobcorn, the cob itself being circa 15% of its dry matter.
Currently, harvesting maize for the grain is mostly done by a combine harvester, ..which typically is a general purpose harvester not specific to the crop, except for the front unit (called a header) which is a separate item.
The maize header does not require much power to function and it delivers cobcorn into the maw of the harvester.
The combine’s threshing rotor requires a great deal of power to function, and in consequence the harvester needs a large engine that necessarily consumes much fuel. ..Many a combine is a big expensive beast of a machine both to buy and to operate. ..The maize header costs far less in comparison.
Attaching a maize header to the front of a truck and running it with an hydraulic motor [or some other way], plus a means of conveying cobcorn into a box behind the cab, would result in a much less expensive harvest.
Alternatively, the header and conveyor may be a pull~type unit offset behind a tractor and delivering cobcorn into a wagon hitched directly behind that tractor. ..This was once the common way of harvesting maize in North America, even up to the 1970s. ..Self~propelled units were also available, some having a dumpbox that was emptied periodically into a truck.
But however cobcorn is harvested, what would complete the scenario is someone to buy it from the farmer, to save him the expense of threshing out the grain. ..In short, what is wanted is a reliable market for cobcorn. _And that depends ultimately on someone having use for the cobs.
A Market for Cobcorn
The most obvious buyer of cobcorn would be an aggregator who would assemble shipload quantities, separating grain from cobs and selling each separately. ..The machine used is specific to maize and does not require much power to strip kernels from the cob, leaving the cobs intact. (This process has been called shelling, though stripping is more descriptive.)
By way of contrast, what a combine harvester does is threshing, which is much more aggressive, breaking the cobs into pieces and using more power in doing so.
But the grain must be sufficiently dry to meet trade standards, and it is not in that condition when coming off the combine harvester on a farm. ..So that farmer must dry it, an extra expense. ..Similarly, cobcorns coming from the field also need drying, though not immediately, and may be sold as is, the buyer then needing to dry them in order to get grain dry enough to meet trade standards.
An inexpensive method is air drying, though this may take some weeks. A locale whose air is usually dry and hot is ideal for this. ..Many places around the Mediterranean fit this description well enough.
Major Buyer of Cobcorn … in a hot, sunny locale:
- Simple scenario —
- strip grain from cobs;
- bin drying of grain with air heated by sun;
- grain sent in shiploads;
- [storage of cobs outdoors for natural dry down];
- grind and pellet cobs: _ship those.
- << Other scenarios for a major buyer appear below.>>
Fermentors
The most likely use of pelleted cobs is in production of a biofuel thru fermentation. ..Only, not ethanol, which rather restricted in the matter of ferment substrates, and expensive to isolate using distillation [which is usual]. ..Far better instead are microbes that can utilise both starch and xylans [or at least xylose]. ..That way, maize cobs alone can be the substrate of choice for the fermenter, avoiding the grain entirely, which some years may be pricey.
A well-known ferment, which circa 1920 was being done on a commercial scale, results in 1-butanol and acetone [propanone]. It is a two.step process, in which butanoic acid is first produced along with acetic acid; this takes perhaps 18 hours. One butanoic acid plus two each of H2 and CO2 are obtained per glucose molecule (or its equivalent).
The butanoic acid may be removed from the ferment by extraction with a suitable solvent such as hexane. A more convenient choice is the ketone of this acid — dipropyl ketone {PPK]. PPK may be got by passing the acid as vapour over a suitable catalyst, of which even CaO is one, though there are better choices.
Alternatively, the Ca salt of the acid releases the ketone when sufficiently heated. Likely passing the extractant + butanoic acid over crushed limestone would provide the calcium salt. And when PPK is the extractant, merely adding water would float it above the brine [of calcium butanoate].
PPK is nearly insoluble in water, blends well with gasoline, and being more energy dense than ethanol would readily displace it as a gasoline companion. Or simply replace gasoline entirely.
Propanone
As for the weak acetic acid solution post extraction of the butanoic acid, it may be transformed by immobilised bacteria to propanone [acetone] at say a temperature of 50 degrees, then have the propanone gathered as condensed vapour — it distils at 56 degrees at one atmosphere.
It would be simple enough to use hydrogen on the propanone to get its alcohol, 2-propanol [also called isopropyl alcohol] which is well known as an effective disinfectant. Hydrogen is, after all, also produced by this ferment, as noted earlier.
Furfural Maker
Furfural is an industrial chemical made from various agricultural materials having a relatively high content of xylans (say, 25% or so). ..Some plants use the bagassee from sugar cane processing, some use maize cobs. ..One such is a new plant in Kenya capable of making 5000 tons of furfural each year solely from maize cobs. (see item on this site: Furfural, on the ‘More Enviro’ menu.)
Some Other Choices
- Better scenario — for a major buyer of cobcorn _(hot, sunny locale)
- kernels being tightly packed on cob, slit or abrade their tops, [perhaps heat using radiant heat or microwaves], then remove much of the starch (say 75%), likely by suction, possibly by water jet or by rolling;
- dry [perhaps agglomerate] starchy bits removed;
- pack and sell containerloads as animal feed or perhaps also as human food;
- air dry cobs [if needed], then grind and pellet the cobs;
- sell to fermenters making biofuel; ..also to furfural makers.
- the cost of equipment is likely less, while sales revenues would be more.
- Extension —
- of the cobs after starch extracted, strip kernels from some of these;
- add this material to other such cobs when pelleting them;
- this provides pellets with more fermentables, thus worth more to fermenters;
- naked cobs may be sold to furfural makers, likely as pellets; …or ….
- extract much of the xylans from some cobs and add to others when pelleting them, which provides pellets with more xylan, worth more to furfural makers;
- compost these extracted cobs for later local sale as ‘natural fertiliser’.
Other Ferments —
Butanediol as a ferment product is another good choice since it is readily transformed into butanone in one simple step.
Perhaps better known as MEK [methyl.ethyl.ketone], ..butanone is a widely used solvent. It would fetch more sold as such, though it can also be [or become] a fuel component. ..As instance, it is readily hydrogenated to form isobutanol, which is also well known as something blendable with gasoline.