Conversion can be skipped for fruits, pure sugar, sugar cane and other feedstocks that do not have starch.
Milling - Conversion first begins by milling, crushing, or otherwise grinding our grain. The point here is to increase surface area and to free the starches from inside their protective cell walls. A grain mill or hammer mill are the best choices. Make sure it is crushed and broken up, but grinding to a fine powder is unnecessary.
Liquefaction - After milling, the grain is diluted and alpha amylase is added. This is our mash. Our mash is brought to boiling, where it is held for twenty to thirty minutes to kill all airborn bacteria, wild yeast, fungus and other microbes. Heat is removed, another small dose of alpha amylase is added to continue the liquefaction. Agitation is delivered by bubbling air through the bottom of our vessel.
pH Adjustment Once liquefaction has finished, pH must be adjusted so that the second enzyme in series will act correctly. Glucoamylase works best in acid environments from pH 4.8 to about 5.2. Outside of these pH ranges, enzyme function is unpredictable. Temperature is also important, as glucoamylase works best around 120F. However, pH is by far the most important. pH is dropped to 5.0 with use of dilute sulfuric acid, muriatic acid or with a pH buffer. Phosphate buffers work extremely well.
Saccharification - The mash is allowed to liquefy until its temperature drops to 140F. When temperature is at 140F, pH is adjusted to 5.0 and glucoamylase is added. Our boiler is then sealed and the mash mixed with a low PSI air agitator. Depending on enzyme loads, saccharification can take from two hours to one day. Insulation is absolutely vital to ensure enzyme temperature requirements are met. After this step, conversion is completed.
Additional Enzymes - Some additional enzymes can convert plant material into usable glucose. Glucanase, xylanase and cellulase degrade a plants cellular wall into simple sugars. Glucanase and cellulase convert plant wall material into glucose. Xylanase converts xylan to xylose. While most yeasts do not metabolize xylose, some do. However, all grains are at least some percentage cellulose and glucan. Depending on feedstock, these enzymes could increase yields significantly. In some feedstocks, no significant increase is to be expected.
Yeast dosage is dependant on sugar content and percent of alcohol we wish to ferment to. Fermentation severely slows past 14%, since alcohol denatures the zymase enzyme. However, some yeasts can ferment up to 21%. Things like sugar and molasses are not very nutrient rich and may require additional yeast nutrients.
Temperature Control - Temperature of the boiler or fermentation vessel (which ever you are using) is best kept at 70F. One method is to first ice the mash after liquefaction. A cooling coil can also be used. Some yeast strains are very temperature tolerant, some are not. For the most part, past 85F, fermentation will cease.
Air Locking and Fermentation Traps - Yeast has two methods of metabolism. When oxygen is present, sugar is consumed and yeast divides. This is a good way of getting our yeast started, but a very bad way of producing alcohol. The best way is to seal the fermenter and run a hose from the top of the fermener into a vessel of water. This way carbon dioxide bubbles up through the water, but no air is able to enter the vessel. The same bucket can be used for cooling reservoir and air locking.
Distillation is the process by which alcohol is separated from the mash and water. It exploits the difference in boiling points of alcohol and water. In a fractionating column, a condenser unit packed with insulating material and strips the water from the vapor. As the water falls, the alcohol vapor continues up the column. When new, hot vapor is introduced from the boiler it is cooled by the falling water. At the same time it revaporizes any of the alcohol that may have condensed in the column. At the top of the column there is another collection unit. This unit is free of insulating material and is kept at 173F. Vacuum distillation also exploits this difference in phase change by lowering the pressure of the entire vessel. As the vessels pressure is lowered, ethanol begins to vaporize at a lower temperature.
Using a Fractionating Column - To distill, heat the boiler and pipe the exhaust into the inlet of the fractionating column. Once the mash has begun to boil, ethanol should come from the fuel outlet attached to the reflux column.
Filtration uses activated carbon to absorb the dangerous organic volatiles yeast also produces. Activated carbons surface area is large enough such that organic compounds are easily trapped. Ethanol and water pass through, unabsorbed.
Filters can be attached directly to the fuel outlet, or you can filter your alcohol after it has been produced using a funnel and a long tube filled with carbon.
Water and alcohol form an azeotrope at atmospheric pressure. Basically, fractional distillation can only achieve a certain proof quality. Past about 94% ethanol, 6% water, distillation is not a viable option. In order to remove the water, we must use either a chemical that does not react with ethanol or use a dessicant. Calcium hydroxide has been suggested as a chemical method of drying ethanol. Another method is to add gasoline to the ethanol and redistill. Both of these options complicate the process and redistillation wastes energy. Corn grits and glycerin have been used to produce absolute ethanol as well, however, the far simplest method is to use a molecular sieve.
Zeolite - Zeolite is a synthetic aluminum-silica material. The surface of which is covered by pores of a certain size. Three angstrom and four angstrom zeolite are suitable for the dehydration of ethanol. The "pore size" of the zeolite gives the critical diameter of the molecules it can adsorb. Three and four angstrom zeolite are usually used as dessicants to remove carbon dioxide and water. The critical diameter of ethanol is 4.4 angstroms. Because of this, its molecules will not fit in the pigeon-holed surface of the zeolite. Water has a critical diameter of around 2.4 and is readily adsorbed. Zeolite is not consumed in the process. It can be regenerated by heating to boiling point of the substance it has adsorbed.
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