From field into biofuel
Maize is commonly used to make biofuel ethanol in the USA, somewhat less so in Europe. It is the starch in the kernels that is converted by microbes into ethanol. Loose grain is what is used, though an alternative would be a better choice — the grain still attached to the cob, call it cobcorn.
Today, a combine harvester is usual delivering only the kernels to be taken from the field. While convenient in its way, this style of harvest is peculiarly expensive with maize.
The combine is a general purpose harvester used in many different crops. It is a mobile thresher being fed material by a detachable front unit, of which there are several types meant for different crops. ..A maize header picks the ears from the plants, strips off the wrap of leaves, then sends cobcorn (naked ears) into the maw of the machine.
The threshing action is much too aggressive, with cobs being broken into small bits. Then freed kernels are gathered and the broken bits of cob ejected. No surprise that threshing is the largest single use of the engine’s power, and a big engine is both necessary and a major cost item of this expensive machine.
If instead cobcorn was wanted, a combine harvester would no longer be used in maize — only the front∙end unit would be, attached to something else.
Cobcorn Harvester
Comparatively little power is used to pick, strip, and deliver cobcorn. A self∙propelled unit may simply be the maize header fronting something like the tractor end of a self∙propelled windrower. A conveyor to a wagon or box receiving the cobcorn completes this picture.
Such a ‘cobcorn harvester’ is a less complex machine with a smaller engine, so less cost to build and then less expensive to buy. Due to much less fuel being used in the field, it also will be cheaper to operate. And there are other cost differences, with yet more fuel saved.
Loose grain coming off the field is often too moist to store safely, and unless dried may rot. Typically, fossil fuel is burnt to heat the air blown through the grain. How much depends on the moisture in the grain, which in part depends on weather conditions at harvest. ..However, any farmer growing a large amount of maize is almost certain to harvest some that is too moist to store safely, because it is impractical to wait for all the crops to dry down to an acceptable level. So these growers will always incur a drying cost, one that varies greatly.
Natural Drying
Drying cobcorn is a breeze comparatively, as it uses natural air circulation. Unlike loose grain which packs closely, cobcorns have much air space around them and air moves through easily. If necessary, fans can blow more unheated air through.
Since cobcorn is less expense to harvest and little expense to dry, it appears that profitability is not the main consideration in choice of harvesting system for maize. ..Evidently, convenience is.
It is inconvenient to harvest ears as cobcorn and store them for many weeks before separating the grain from the cobs. ..However, one positive aspect is lower cost, a lower investment in portable machinery specific for maize, particularly when using a smaller capacity machine over a longer run of days. ..And if it is powered by electricity, this would further reduce total fuel use of the farm.
Clearly, no one focussed on profits first, last and always would use a combine harvester in maize. This creates doubt whether farmers actually are capitalists… even though most economists presume they must be. It is part of orthodox economics doctrine, which is quasi~religious in nature. __Economics is not, and can never become, a science.
Fermenting Using Cobcorn
Ethanol Production:
Currently, maize as bulk grain (loose kernels) is what is often the source of starch to be made into ethanol, using strains of yeast that don’t feast on starch directly. ..Instead, enzymes are employed in a two·step process that breaks down the starch polymer into glucose components of a size sufficiently small for that yeast to use for its own growth, during which it ejects ethanol as a waste product.
In the first step an enzyme called alpha amylase is used, typically at a temperature of ~88°C. This converts the starch as a solid into a solution of less lengthy units (dextrin) that is handled as a liquid. Talk about a hot bath! ..A second enzyme is needed later to break the dextrin down into something the yeast itself can consume.
Cobcorn instead of bulk grain may be used in this first step: _ all that’s required is having the hot water with enzyme contact the starch inside each kernel. Slicing the top or punching a large enough hole in it will provide such access. ..When the dextrin solution created is led away, much solid starch will remain behind. Repeating this several times slowly erodes all the solid starch until essentially none remains.
The soggy cobs can easily be reduced to mush and may be fed to a furfural digester to produce that valuable chemical. Else otherwise dealt with. _[A good choice would be fermenting it to butanoic acid….]
Alternative Ferments:
Ethanol quite frankly is not a good enough engine fuel due to its low energy density. Also, it tends to be costly to make when starch is the substrate, since starchy grains are much used for swine and poultry feed, and maize is a major export from the USA. So it is not often very cheap.
Certainly there is room for alternatives, particularly fuels with greater energy density. The best choice very likely is di:propyl ketone (PPK) made from butanoic acid. _An old British Patent [565,773] describes a septic ferment using wild microbes plus one bacteria making primarily butanoic acid. One that converts lactic acid directly into the butanoic is especially appropriate [US Patent 4.138.498].
PPK is more energy dense [C7.H14.O] than ethanol [C2.H6.O], and barely water soluble. Both attributes make it make it a better additive to gasoline than anhydrous ethanol. Moreover, cheap materials such as chaff and straw, or maize cobs, may be the substrate instead of expensive starchy grains typically used by ethanol producers. _Another possibility is an energy crop such ornamental sunflowers [5+ m tall] or sunroot, which is effectively perennial though not quite so tall.
Another is 2,3·butanediol, which readily dehydrates to butanone, perhaps better known as the solvent MEK (methyl ethyl ketone) which is similar to acetone but slower to evaporate.
Reacting MEK with the diol yields a five·member ring having a high octane rating. It is a cyclic di·ether with attachments: one ethyl and three methyl, an excellent gasoline component for today’s auto engines. ..When acetone is instead the ketone employed, a similar product is obtained having four methyl attachments.
Though not yet a commercial reality, a thermophyllic bacteria that takes in acetic acid and releases acetone is likely to become available. Here, the acetone would escape overhead as vapour and be condensed. It would be remarkably inexpensive to produce, and combining it with the butanediol should give a cheap biofuel for today’s gasoline engines.