In the spirit of ultralight backpacking, I am not taking a stove with a butane or propane canister. I will make a fire with downed wood, or I won't have a fire at all. That's been my motto anyway. But what if I go backpacking in the desert and can't find wood? What if I kill a rattlesnake and can't find a way to cook it? What then? Have a spare bit of fuel, that's what.

For those that want to carry all their fuel in, there is a good weight analysis comparing alcohol based stoves vs butane canister based stoves:
https://adventuresinstoving.blogspot.com/2017/02/gas-vs-alcohol-which-is-lighter.html

Potential energy vs weight for different fuels (although this says nothing of power or burning temperature).
source, and recommended reading plus my own additions.

However, because solid fuels burn less cleanly, a lot of energy is wasted, and the above chart doesn't take that into account in the data for Kcal/g. Incomplete combustion produces a lot of soot. Achieving complete combustion has a lot to do with the design of the stove. A well designed stove would allow sufficient oxygen for complete combustion. This is noted in the commentary, in the an article covering time-to-boil and resulting sootiness of different brands of fuel.

Liquid fuels used on the trail include denatured ethanol, methanol, and isopropanol. Although, isopropanol is not preferred, as it leaves soot residue on the pot: “It is possible to design a stove to burn the 91% isopropanol cleanly, but it's a very different design, and much harder to build, than the simple soda can stoves we all use. It neads a generator tube to preheat and vaporize the fuel (because of the lower vapor pressure) and a venturi to premix the fuel vapor and air.” source

The favorite liquid fuel is ethanol. It burns cleanly and isn't as toxic as isopropanol or methanol. Unfortunately, in some countries pure ethanol is very expensive unless it is denatured, and for denatured ethanol the percentage of ethanol is rarely listed. However, ethanol is ubiquitous. You would be hard pressed not to be able to find it, compared to a backpacking propane canister.

Solid fuels include esbit (hexamine) or paraffin wax infused cotton. Solid fuels weigh less overall because they do not need a bottle for storage, and they also take up less space. While solid fuels don't burn as cleanly as liquid fuels, you can use sand and dirt to scrub most of it off. But to avoid that completely, you can use some aluminum foil to cover the bottom of the pot.

I take both solid fuel and a small bottle of ethanol, but my main fuel is firewood.

The weight of my wood chopping tool is an unbelievable zero grams.

Large wood can be made into shorter lengths by slamming it against a rock edge. It's a lot faster than any saw or axe. It can even be a rock without a sharp edge. The kinetic energy of the end of the log will make for quick work. Thinner branches can be broken by holding one end and stepping on them with the ground as leverage.

Candle wax cotton balls are home-made. You use a double boiler to melt the wax, then dip the cotton. Place the result into a zip lock, for use at the campsite. It's a great way to take advantage of the used candle wax after waxing your bicycle chain.

While you can use liquid fuel based stoves (see can of cat food in image below), I mostly use it as a fire starter. Ethanol can also be used for personal hygiene. I douse a cotton pad with alcohol, “sanitize” my armpits, then light it up under some kindling. The burn will last a minute or two, enough to get the fire going. I've had one incident where this didn't work, because it had rained and there wasn't sufficient kindling laying around to light up the larger wet wood. Alcohol also works less well if it's really cold. In those cases, you will be better served by the solid fuel.

You can safely store your 95% ethanol in either #1 LDPE or #2 HDPE plastic bottles.

Campfire stones will shield the wind, and can also support cookware. Even in the desert, you can dig a pit in the sand. If you can't manage a few rocks of the same height to keep your pot over the fire, you can always use your tent stakes as a stand for the pot. This makes for the best ultralight stove.

If there is no firewood anywhere in sight, then you can use either an alcohol or solid fuel option. A canister stove is too civilized for me. My life doesn't revolve around food. A canister is also really noisy. You'll only hear water start to boil with the alcohol or solid fuel options.

If you are one that must bring along a stove, this is a good site to research options: http://zenstoves.net/StoveSystems.htm
A great video review of alcohol vs gas stoves: https://www.youtube.com/watch?v=STyM5xKf5cU
There are just so many good sites about stoves:
Stove Comparison – Real World Use, Paul Mags 2018
Rumors, Myths & Lies of the Alcohol Stove

“The “best stove” depends on what you use it for at a given time and activity. Boiling a lot of water? Backpacking as a couple? Doing “real” cooking in the backcountry? Long time without resupply? Winter camping?” - Paul Mags

Since I prefer a campfire and will rarely use an independent stove, the option of packing an alcohol stove or solid fuel would be an overall weight savings for me compared to a canister stove. With the alcohol stove, I bring along a few more ounces of alcohol, and a stove that weighs next to nothing.

Unlike a canister stove or alcohol stove, the solid fuel provides fire but no stand for the pot. But that's what rocks, sticks, or tent stakes are for.

For a liquid fuel you need a stove, and my favorite design is the penny can stove constructed in this video by juijitsu2000. An alternate design. The pressurized jets help mix the air and fuel (though not well enough for using isopropyl alcohol without producing soot).

Fiberglass or carbon felt wicking material inside the stove will help with accidental spills by acting as a sponge. The sponge will also keep the jets from burning a foot high when adjusting the placement of the stove. Lastly, the sponge acts as a seed site that enables fuel evaporation (what's the word?), which helps prime the stove more quickly. Some Trangia knock-offs on Amazon lack the internal “sponge” and thus take really long to prime, wasting fuel in the process, at least according to one Amazon review.

A small gap between the windscreen and the pot will improve heat transfer by channeling the heat from the flame.

An inch gap between stove and bottom of the pot will give the gas sufficient time to fully combust before going up against the cooler pot surface. The pot stand also keeps you from jostling the stove when stirring food in your pot, although this is not as necessary if there is wicking material inside the stove.

Stoves that have a sealing screw-on lid can be used for fuel storage. Although, even a larger alcohol stove holds at most 4 oz of fuel.

More stove designs: https://bikepacking.com/gear/hop-can-stoves-how-to-make-5-ultralight-bikepacking-stoves

I really admire the Jetboil cooking systems, like the MicroMo or the Sumo, with their integrated heat exchangers to improve fuel efficiency. I would get one if the cooking pot could also be used as a water bottle. A hard sided water bottle or a pot takes up a lot of space, and bringing BOTH along seems like overkill. Although the lid is snug on the Jetboil pot, it has steam holes and a drinking hole which remain open. With the Jetboil pot mounted in the backpack side pocket, if I leaned over the water would spill. I am not an ultralight purist and will sacrifice weight for added conveniences, but an entire pot worth of unnecessary volume is too much.

Jerry Adams 1.3 oz heat exchanger design (image below) increased fuel efficiency by 10%. Over 10 meals meals, that would save 1 oz of fuel? It can't be that little! Mark Fowler and David Thomas increased fuel efficiency by 30% with commercial 1 liter heat exchanger pots that weigh around 7 oz.

I've thought of cutting into an insulated stainless steel water bottle, using the air gap between the internal and external vessels to channel heat from the stove. All airflow would go through the interior of the bottle. The insulated water bottle would sit right on the stove and have a lower intake and upper exhaust vents. A small windscreen would fit snugly around the bottom diameter of the bottle (perhaps with a twist tie), and the pressurized stove pinhole vents would channel the flame upward through the insulation gap of the bottle.

The Hydro Flask Lightweight and the GSI Outdoors MicroLite, which are vacuum insulated and weight 11 oz, could be converted into “bottle pots”. Compare that to 5oz titanium cooking pots, and a 6oz heat exchanger from MSR. I was hoping for a cheap insulated bottle to experiment on. Cheap ones usually have the added benefit of being lightweight.

However, a vacuum insulated “bottle pot” would not work well by my preferred method of cooking, which is to set the pot in the fire pit, next to the fire. The double wall would insulate the inner pot from the radiant heat of the fire. Radiant energy absorption on a single wall bottle could be further improved with black anodizing. Although, despite being bare stainless, I still get boiling water in under 10 minutes, which is fine with me.

Another method I'd like to try, is to substitute the campfire with solid fuel sitting 3 inches away from the bottle pot, and a reflective windscreen using the bottle as part of the total circumference. This would concentrate the radiant energy from the solid fuel onto the side of the bottle. If this works well enough, it would be the best of all worlds, as I only need a reflective windscreen as the only extra besides the fuel. No alcohol stove, pot stand, or heat exchanger needed. Hopefully the soot will rise and not collect much on the exposed side of the bottle and the windscreen. Fuel efficiency would probably be poor, but I don't like my food too hot anyway.

I usually don't use a pot. I just bring fuel. No pot, no pot stand, no heat shield, no canister or alcohol stove. I make due with whatever fire pit I can make. So how do I cook without a pot, you might ask?

I boil water and cook food in my wide mouth stainless steel water bottle, that is also my water bottle. I stand the bottle right next to the campfire inside the stone shields of the fire ring. I have a super long bamboo spoon for stirring all the way at the bottom, steadying the bottle with a stick or a wool sock puppet. A piece of 2mm aluminum wire twist tied around the upper lip of the bottle is used as a pot holder. I use the wire to lift the hot bottle out from the side of the fire and into the hand-made reflectix pot cozy, which allows me to hold the bottle with my hand and eat from it. There is also a Microgripper pot holder available from GSI. A bandana would work, but I find it hard to hold just right to avoid being burned.

In the case where I can't find firewood I can use one of my fuels.

With solid fuel, I protect the water bottle from the soot by wrapping it in aluminum foil. I wrap the bottle from the top to the bottom and back up, folding the sides over and hooking the foil over the top. Sometimes I use the pot-holder wire to hang the bottle over the solid fuel, by one of many methods. After cooking, I stow the aluminum foil with the soot folded inward, for later reuse.

When I bring a side burner alcohol stove, the bottle sits right on the stove. An aluminum foil windscreen wraps closely around the bottle, channeling the heat from the stove near the surface of the bottle. Be wary of strong winds because of the lack of stability. Update: Looks like someone figured out how to use a larger diameter stove to increase stability: Ring of Fire stove & Klean Kanteen. Both of these stoves use wicking material that contains the alcohol even if the stove is tipped over by accident.

While a soft bottle/bladder is a lot lighter and collapsible, I can't stand the taste of plastic, and prefer stainless steel. I have the Stanley Adventure Stainless Steel water bottle (not insulated; no longer made). It weighs 8.5 oz. I could get the Vargo Bot-HD Titanium Bottle and Pot Combination, but I would only save 3oz, and it costs $109.95 (because $110 would be too much). Aliexpress has a Lixada titanium pot for $26 that is only 4.8 oz, but it doesn't have a lid that seals for use as a water bottle. Aesthetically, I like the Stanley better, and the cover has a loop that's more convenient for securing to my pack.

After researching the possible use of foil in the oven section below, I thought to design a collapsible stainless steel foil pot for boiling water and cooking. I will be testing its ability to not fall over. Following the video instructions for folding foil into a pouch, I think you could make an extra fold at the bottom, which will allow the base to expand and allow it to stand upright as a cooking pot. Will the triple fold on the sides of the pouch hold water? I'm sure it will with a little jb weld. Some grommets would allow for a hanging wire.

Bear Minimum came up with a collapsible origami pot made of fiberglass and non-stick coating, with an aluminum base. Compared to the bottle pots, you get a wider base for efficient heat transfer instead of a tight fitting windscreen for channeling heat. With one side down, you also get a good surface for use as a pan (which you can flip burgers on).

Regarding the Caldera Cone

I went with the Stanley bottle pot, because I already own it. With the Stanley I can cold soak dehydrated food, but not with the folding Bear Minimum pot. Cold soaking prior to cooking increases fuel efficiency, since you only need to warm up your rehydrated food. As an alternative, you can put a silicone lid on your own pot. A few redditors recommend it.

If I forget to cold soak food to save fuel, the pot cozy can do the same after heating up the food instead of before. Instead of simmering your food until it rehydrates, you can cut off your stove and let it sit in the cozy which will keep it warm.

The Stanley comes with a plastic lid, which unlike the Vargo Bottle Pot, I won't use for cooking. I could use a DIY aluminum foil lid to save weight, but I prefer to use the lid from a glass jar instead, which is also my feline hiking buddy's water or food bowl.

The following image by Yumi Sakugawa, with several nifty cookware ideas. Just substitute aluminum foil with stainless steel foil as a stronger and healthier option.

Aluminum foil, or Stainless Steel Tool Wrap makes for an excellent oven. First use a stick to move some ash and embers to the side. Then wrap your food inside of the foil and place it in the firepit. Cover the foil with the same ash and embers and your meal is ready within a few minutes. This works really well for sweet potatoes.

Thickness of heavy duty foils

Aluminized Mylar pouches will melt

The following video shows how to make a pouch that will be your oven.

Aluminum can leach into food, but one study found that baking food wrapped in aluminum foil added very minute amounts. The study states that contamination is real and present, but it would be hard to reach the 2mg/kg daily limit for aluminum by baking in aluminum foil. For a variety of reasons, it's healthier to cook at lower temperatures. In the case of boiling water, which guarantees 100C, you don't have to worry about aluminum. Acidic sauces, however, leach aluminum significantly. Stainless Steel Tool Wrap is a healthier option, but is more expensive.

About the daily limit for aluminum intake

I got some 2 mil stainless steel foil, and I recommend looking for something less thick, like 1 mil, the same as heavy duty aluminum foil. Steel is stronger and heavier than aluminum, so it will be even sturdier than aluminum. I made a 16.5cm x 19cm sleeve, and it weighs a whopping 33g (1.16oz). It's hard to spread the bottom open, but once spread it stands up really well as shown in the following photo. It's so strong that the form doesn't change if water is poured in. Though I won't be using it to contain water; I just plan on throwing it into the campfire embers with stir fry veggies. The top edge is folded over once so it doesn't have a sharp edge.

I did a quick look for a source, and then also asked on quora. 1 mil stainless steel foil in 12” width or wider does not seem to be a mainstream commodity.

Rotisserie, aka spit roasting, is also an excellent ultralight choice. Weighs zero grams and occupies no space in your pack. It's not very expensive either.

A great idea for a base camp where you are spending your day at camp and can take advantage of an overhead sun.

https://www.builditsolar.com/Projects/Cooking/cooking.htm
https://solarcooking.fandom.com/wiki/Solar_Cooking_Wiki_(Home)

You could use a reflective tarp by hanging the corners in a way that they focus heat from the sun towards a central spot where you have your pot. An infrared thermometer can be used to determine the optimal height of the pot. A reflective tarp is often used as a ground cover to warm up a tent, or hung behind you as you sit facing the fire, to reflect heat from the fire to your back side.

If you want to get a dedicated ultralight solar oven, the future is now. The 3 oz Silver Balloon Mini Cooker.

Left image source: If Astronauts Eat It, Why Shouldn’t You? thefutureoffoods.com. Right image source: Walmart.

A luxury item for cold rehydration is a food storage container, which could be used for eating delicacies such as oatmeal. The Preserve one above has a capacity of 19 oz and weight 2.88 oz.

Though all the heating options previously covered are awesome, You may want to focus on ultralight backpacking and do without cooking. Instead of a “bottle pot”, you only bring a collapsible/soft water bladder that weighs 1.3 oz, and if you don't want to eat out of a zip-lock, a separate bowl that seals air-tight. You can eat cold food, including cold rehydration for prepackaged meals.

“Depending on the type of meal, water temperature, and the ambient temperature, it will take 15 minutes to an hour to rehydrate your food.” Before you arrive at your campsite, while hiking, you can add water to your meal pouch or bowl.

Cold rehydration may be your only option if you don't have fuel, or your environment can't produce a fire. Even if you choose to pack for cold rehydration exclusively, when you find wood for a campfire, you can still cook the shelter rats on a campfire stick.

Thoroughness in cleaning may depend on having a nearby water source. You can bring along a small eye dropper bottle filled with a biodegradable dishwashing soap such as Dr. Bronners, and a small scouring pad. You can start the cleaning process with dried leaves or whatever is around you. If running low on water, you have the option of using a wet wipe. Further cleaning can happen at the next water source.

If you don't have aluminum foil to protect your pot, coating the outside of your pot with liquid soap before cooking will later help remove the soot easily.

You can sleep with your food close to you, in your tent, but that may attract mice, bears, or wild boar. If beasts can't smell your food, they won't tear at your equipment to get to your food. Although, if you cook in your tent vestibule during the rain, your entire tent will smell like food. However, even if you continue to cook in the vestibule, it's good to store your food in scent-proof bags. Ursack makes supposedly scent-proof bags they call Opsaks, but you can get the same using much less expensive and more durable oven roasting bags. See mentions of oven roasting bags at: reddit thread and whiteblaze thread. Oven bags are made of either Nylon (polyamide) or Polyester source. Though I wish there was something with a sliding zipper. I really love zip locks with a sliding zipper.

“Backpackinglight tested OPSACK “odor-proof” barrier bags, (LOKSACK Inc.) vs Meijer reclosable quart storage bag as controls. They used drug sniffing dogs under controlled circumstances. When analyzed statistically, these results were not significantly different between groups. Average search times were 86 seconds in the odor-proof group and 84 seconds in the control group. Again, results were not significantly different between groups. In short, OPsacks were a failure. An expensive waste of money.” Colter on whiteblaze.net.

Perhaps just by having food in proximity to the bag, while inserting food into the bag, leaves odor particles on the outside of the bag, which dogs can sniff. Perhaps the oven roasting bags are more scent proof than a regular zip-lock, but either one is sufficiently effective?

Matt Shafter uses 6 mil LDPE (low density polyethylene) zip locks (plymor brand). Most zip locks are made of polyethylene. I love Hefty slider 2.5 gallon bags, but according to Lowe's they are 0.9mil thick, though the official hefty site doesn't say, and I've seen online claims up to 3 mil. Oven roasting bags are super thin, but must be more odor proof per mil of thickness.

Maui Rhino at whiteblaze.net: “I use nylofume bags obtained from my local pest control company. They give them to their clients to bag food prior to fumigating for termites. A couple of years ago, I was camped at a popular lake in the Sierra. After going to bed, I heard some rustling, and realized a mouse was after a bag of trail mix I'd forgotten to put in the bear can. I tried scaring it away a couple times, but it always came right back. As an experiment, I put it in a nylofume bag, and set it right back in the same spot. The mouse never paid any more attention to it the rest of the night.” Just like oven roasting bags, nylofume bags are made of nylon.

There is too much pseudo-science, and we need only look at better science for answers. Which leads to the section below.

This table, shown below, from Food Packaging Permeability Behaviour: A Report, Valentina Siracusa 2012 shows that LDPE has the lowest relative gas permeability. What does that mean? “Calculation of relative permeability allows comparison of the different abilities of fluids to flow in the presence of each other, since the presence of more than one fluid generally inhibits flow.” source Below the “Relative value of permeabilities for the most commercial polymer (no-dimensional value)”. It's strange that a low density plastic (LDPE) would be less permeable than a high density one. Thus, I guess that a higher number means less permeable.

To avoid delving into something really complicated, it's best to find a study that deals exactly in what you are wanting to know, like:
Odor Barrier Properties of Multi-Layer Packaging Films at Different Relative Humidities, Hatzidimitriu et al 1987
Preliminary quantification of the permeability, solubility and diffusion coefficients of major aroma compounds present in herbs through various plastic packaging materials, Leelaphiwat et al 2018

Mylar, which is a composite of layered materials, would be a much better choice as an odor barrier bag. Mylar is a ton less gas permeable than plastics: Mylar Product Information, because a layer of metal is much less permeable than any plastic. Perhaps the main reason for using plastics for food storage is the convenience to easily see the contents within.

• Definitely stay away from camping spots with high traffic, as mice will chew through your tent out of habit. Not in trail shelters, nor anywhere near shelters. Only visit shelters with your feline hiking buddy.
• A bear bag or canister will annoy bears to no end, just make sure they don't hear you laugh or you may be in trouble. Canisters are way heavy and bulky, and you never know if you come across the Einstein of bears.

Dig a hole in the ground, and place perishables in a bear resistant bag like the Ursack. Cover. Avoid constantly looking in the fridge when you have the munchies. Preservation can be further assisted by curing (salting), dehydrating, storing in lard, and biltong.

I'm not a fan of microwaves, but if you are, there's a 2.6 pound microwave for you. I'm definitely passing on this one.

http://www.wayvtech.com

You can take along everything but the kitchen sink.