Alcohol-fueled camping stoves
My main criteria for a camping stove is safety, followed closely by sustainability of the fuel. People drink certain kinds of alcohol regularly and typically don't consume petroleum-derived fuels without severe adverse reactions. And since alcohol can be made from corn and other agricultural products, its renewable.
Fuel
There are a lot of fuel alcohols, but I exclusively use the one used in beverages, ethanol. In general, safety, burn temperature, availability, and price are the factors that determine which fuel to use.
In addition to ethanol, methanol and isopropanol (isopropyl alcohol) are used as stove fuel. While these fuels are cheap compared to ethanol, they're also toxic. Because ethanol is a controlled substance, it's typically heavily taxed. To make ethanol for industrial purposes cost-effective, it's made unfit for consumption, or denatured, using methanol or bitterants. Methanol is a neurotoxin. An embittered ethanol mix like Bitrex would be reasonable, but it's not available in the United States. And isopropyl alcohol burns incompletely, with a carbon smell and soot that fouls cookware.
As an aside, in 2019 California enacted a limited ban on denatured alcohol products for use in commercial applications like paint stripping and thinning. VOCs from alcohol drying contribute to ground-level ozone, or smog, so the California Air Resources Board limited its availability. The ensuing confusion made it scarce for use as fuel and distributors learned to label it as a fuel, instead of just "denatured alcohol." As of 2021, REI sells denatured alcohol in their stove section, so the brief blip seems to have been corrected.
The most accessible pure ethanol fuel is Everclear 151, a grain alcohol that's about 75% ethanol by volume. It's a drinkable spirit alcohol and can burn, but is difficult to ignite and takes a long time to boil water. Everclear 190 would be better, with 95% alcohol by volume, but it's not legal to sell in my state, California.
Instead, I've started buying from Culinary Solvent, which ships food-safe ethanol across state lines for non-beverage uses. Expect to pay $30-per-liter, a far cry from the $5-per-liter methylated spirits from West Marine or REI.
You can also make ethanol at home, but it's difficult and expensive to reach a fuel-grade concentration. The Mother Earth News has a page about Alcohol as an Engine Fuel and Tech Ingredients shows a complex system for distilling ethanol.
Stoves
With the fuel issues out of the way, the next concern is which stove to put it in. It's easy to make a usable alcohol stove out of a soda can, and there are a lot of good guides:
Some alcohol stoves in this style are even sold commercially:
I built a penny stove out of a soda can in 2007 and it ran great. But since 2017, I've been using an Evernew Titanium Alcohol Stove. I complement it with a Ti Trivet, and I've been happy with it, though it can be tricky to light with a butane lighter.
It would be nice to have some kind of simmer control on the stove, which is a relatively rare feature. And an indicator wire like on some isobutane stoves would help tell if the stove is lit.
I may eventually get around to trying these other alcohol stoves:
Fishbone Bioethanol Stoves come with a simmer knob, like a propane stove. Ships use stoves like these because, unlike propane or butane, alcohol vapors are lighter than air and can't collect near the (electrical, potentially sparking) bilge. Origo was the most popular alcohol stove option because it can be gimbaled to stay level on rough seas and doesn't use pressurized alcohol. Unfortunately, their production was bought by Dometic in 2017 and the stoves were discontinued in 2019.
Project Gaia is working with CleanCook and Blue Flame Stoves to provide alcohol-fueled stoves for countries that cook with firewood or petrochemical fuels. If these stoves are ever made available in the United States, they'd make great camp stoves.
In chemistry, alcohol lamps are commonly used to produce a low-intensity heat and light source. Their use is described in How to Make/Modify and Use an Alcohol Lamp.
Usage
Never fill an alcohol stove when it's hot -- the alcohol can vaporize and ignite unexpectedly. To light a stove without a long neck lighter, light some alcohol on the side of a knife and pour it into the stove. Never blow out an alcohol flame because it can disturb the liquid and cause a fire. Instead, snuff out the flame to extinguish it. Throwing water to extinguish an alcohol fire can work, as alcohol will absorb the water and become inert, but it will unpredictably spread the flame until the fire goes out. A windscreen improves efficiency and helps control the flame. Practice using the stove at home.
Because most alcohol stoves lack a valve to control the fuel supply, they can be illegal when the risk of wildfire is high.