Alcohol & Ethanol Production

01

What fermentation actually is

Yeast eats sugar and produces ethanol and carbon dioxide. That's the whole reaction, and everything else is management of the conditions it happens in.

So the first question is always where the sugar comes from. Fruit has it directly, which is why fruit wines and ciders are the simplest ferments there are. Grain and roots hold starch instead, which yeast cannot use, so those need converting to sugar first, by malting, by enzyme, or by cooking. Honey, cane and beet give sugar directly.

Yeast needs more than sugar: a temperature range it tolerates, some nutrients, and an environment other organisms don't take over. Wild yeasts are everywhere and produce unpredictable results, which is why cultured yeast is used when you want the same outcome twice. Traditional ferments that rely on wild yeast are working with a local population that has effectively been selected over generations.

Ethanol eventually stops the process. Yeast poisons itself with its own product at a concentration that depends on the strain, which is the ceiling for any ferment and the reason distillation exists.

02

Running a ferment well

Fermentation is forgiving and it rewards a small amount of control, and the four variables are cleanliness, temperature, oxygen and time.

Cleanliness is first because you're growing one organism and excluding others. Everything the ferment touches should be clean and sanitised, and the vessel should be closed to the air while still letting carbon dioxide out. An airlock does exactly that, and a cloth cover over a bucket is the low-technology version.

Temperature decides both speed and flavour. Too cold and yeast stalls; too warm and it produces off flavours and can die. Steady beats warm, and a ferment in a stable cool place usually turns out better than one in a warm fluctuating one.

Oxygen is wanted at the start, when yeast is multiplying, and unwanted afterwards, when it turns alcohol into vinegar. That's the whole reason for aerating a fresh must and then sealing it.

Then leave it alone. Most home ferments are interfered with too much, and the commonest fault is bottling before fermentation has genuinely finished, which produces pressure in a sealed container.

03

What distillation does, and does not do

Distillation separates by boiling point. Ethanol boils lower than water, so heating a ferment produces a vapour richer in ethanol than the liquid, and condensing that vapour gives a stronger product.

What it cannot do is create anything. Everything in the distillate was in the ferment, in different proportions. That's the single most important thing to understand about it, and it's why a poor ferment cannot be rescued by distilling and why contaminants get concentrated rather than removed.

The separation is imperfect, which is why the run comes over in a sequence. The earliest fraction is richest in the most volatile compounds, including methanol, and is discarded. The middle fraction is the usable one. The tail is weaker and carries heavier compounds and is either discarded or kept back for the next run.

Judging where those cuts fall is the actual skill of distilling, and it's the part that must be learned properly and not approximated. It's also the part on which the safety of the result depends.

04

Alcohol as fuel

Ethanol burns cleanly, can be made from almost any surplus carbohydrate, and is one of the few liquid fuels a household can genuinely produce.

For burning in a lamp or a stove, the requirement is simply that it's strong enough to sustain a flame, and the burner design does the rest. This is by far the easiest fuel use and it needs no special purity.

For an engine the bar is higher. Water in the fuel is the problem, ordinary distillation cannot remove the last of it because ethanol and water form a mixture that boils together, and engines need adjustment to run on it. It's entirely possible and it's a considerably larger project than making lamp fuel.

The feedstock question is what decides whether it's worth doing at all. Fuel alcohol from a genuine surplus, spoiled fruit, waste starch, a crop that would otherwise rot, is a gain. Growing a crop specifically to convert it is an energy calculation that frequently does not come out in your favour, and it's worth doing that arithmetic honestly before committing land to it.

05

Preserving, extracting and disinfecting

The uses that don't involve burning or drinking are the ones most worth having, and they need modest strength, not high purity.

As a preservative, alcohol stops microbial growth, which is why fruit kept in spirit lasts and why tinctures keep for years. It's also a solvent that extracts compounds water cannot reach, which is the entire basis of tincture-making and why it appears throughout herbal practice.

As an antiseptic it's genuinely effective, and its effectiveness depends on concentration in a way that surprises people: alcohol that's too strong evaporates before it works and is less effective than a somewhat diluted solution. Neat spirit is not the best answer.

And as a cleaning solvent it removes what water leaves behind, which makes it useful for degreasing, for cleaning equipment and for surfaces where water would cause problems.