Thursday, September 10, 2020

Canned Heat

While helping a friend with some camping gear, I was asked to explain the difference between the various “canned” gasses used in camp lanterns and stoves. This friend didn't want to deal with a liquid fuel like diesel fuel, kerosene, or gasoline (which is my first choice) and was looking at the butane and propane options on the market. 

Pressurized cans of fuel gas are fairly easy to find and store well in a cool, dry location for decades, so they make a good choice for emergency supplies. I've used several types of propane canisters for heating over the years and have seen the butane models, so I did some digging and here are the results.

Often called LP gas, sometimes defined as Liquid Propane and other times Low Pressure or Liquefied Petroleum gas, propane has been in use for a little over a hundred years and is commonly found just about anywhere in the world. A popular cooking fuel, it is cheap and easy to transport in steel cylinders that vary in size from less than a pound to several hundred gallons. You'll find a Propane cylinder attached to every gas grill in almost every garage in the US, so it is very common.

Propane has a chemical structure of C3H8, with a boiling point of -42° F. It produces around 2.22 MJ/mol (don't sweat the units, just make sure to use the same ones when comparing) of heat when it burns. Explosive limits are between 2.3 and 9.5% in air. Above or below that range, the mixture is either too lean or too rich to ignite.

Commonly used as a cooking fuel in Asia and in disposable lighters around the world, Butane is another liquefied gas that is easy to store. There are several brands of camping stoves and lighters that use Butane cylinders for fuel and the cylinders are fairly easy to find.

Butane has a chemical structure of C4H10 and a boiling point of 30° F. It has the capacity to produce about 2.88 MJ/mol of heat. Explosive limits are 1.8 to 8.4% in air.

Compare and Contrast
Both Propane and Butane are naturally odorless, colorless gasses that will have a chemical added to make it easy to detect leaks. Methyl Mercaptan is the most common odorant, and it's the same chemical that they add to natural gas to identify leaks. I'd bet that everyone has smelled either a propane or natural gas stove before the flame is lit, as it's a very distinct odor. Both are also a gas at normal room temperature and pressure, and are easily compressed into a liquid and stored under pressure.

Comparing the two, they produce about the same amount of heat and have similar (narrow) explosive limits, so either one will work well as a fuel source for back-up heat or light. The major deciding factor is the temperature that you will be expecting to use it at. 
  • Propane will continue to “boil” inside the cylinder and, in my experience, produce usable amounts of gas down to about -5° F. Below that, you have to warm the cylinder to get it to work. 
  • Butane shuts down at about 40° F, as anyone who has tried to use a disposable lighter in the winter will attest. 
If you live where the temperature drops below freezing, Propane is the better option for large containers. Butane in small containers like a lighter can be kept close to your body to keep it warm, but as soon as you remove it and start to use it in cold weather it will shut down.
Butane cylinders for a camp stove are selling for about $2.00/8 oz ($4.00/pound) can right now, and Propane in small canisters is selling for around $8.00/16 oz. By buying an adapter and a larger, refillable Propane tank you can cut the price drastically, but your local supplier prices are not something I can check; around here a 17 pound refillable canister costs about $35.00 empty and takes another $2.00/ pound to fill.

My Recommendation
My choice is Propane, due to the climate I live in and the ease of storing large quantities of it. I have a grill-sized cylinder that I had filled over 20 years ago which is still full (it came out of a camper when it got scrapped).

However, if you're looking for something to put into a pack or GHB and you live in a more temperate climate, then either one will work.

1 comment:

  1. The 3 major gaseous fuels for portable stoves and camp equipment are propane, butane, and isobutane. The third, which you didn't cover, is a mixture of butane and propane that has more energy than pure propane, but is gaseous at a lower temperature than pure butane. It's typically sold in flat cylindrical tanks, primarily for "Jetboil" type camp stoves.

    I have adapters between the tall butane canisters, screw-on propane canisters, and screw-on isobutane canisters, so I can run a stove or lantern or heater on whichever fuel I happen to have, so long as it's warm enough for the fuel to be gaseous. Also for some odd reason, isobutane must be shipped as a hazmat, while butane doesn't have to be, so shipping a case of canisters is EXPENSIVE for Jetboil, but pretty darned cheap for common butane stove fuel (GasOne, etc.) I buy it by the case for my kitchen butane torch and various other devices, such as a small space heater similar to a Mr. Heater, but designed for butane instead of propane. I have an adapter to let an isobutane stove use butane, and a butane stove use isobutane or propane.

    Then there's the couple of alcohol stoves I have, and the Solo biomass rocket stove, and the compact grills for use over campfires...not going to be without a way to cook, or make coffee, which of the two is the far more important purpose. Without coffee, one doesn't have the will to eat. ;)


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