Back-country Stoves – Fuel Consumption

Back-country Stoves – Fuel Consumption
April 18, 2015 Webmaster

It seems that the question of how much fuel to bring on a trip receives incredibly divergent answers. I have heard quotes of as little as 60 ml per day per person to 750 ml per pair per night. In an attempt to find a reasonable solution, I conducted a fairly simple experiment to develop a rule of thumb that can be relied on is verified by actual experience. The goal is to in fact create two rules of thumb for fuel consumption based on the following assumptions:

  • All meals are typical back-country meals such as instant mash, couscous, soup, instant rice, boil in a bag, etc.
  • Water is not purified by boiling.

The two rules of thumb are:

  1. Fuel required per day for a pair (2) of people with a liquid water supply (stream or pond). The pair requires 1L of boiled water in the morning and 2L of boiled water in the evening. The boiling of water is the extent of the cooking. All other water is drunk cold and purified using other  means, if at all.
  2. Fuel required per day for a pair (2) of people who need to melt snow (snow is not purified by boiling). The pair requires 1L of boiled water in the morning and 2L of boiled water in the evening. The pair also requires 3L of melted snow for consumption during the day (a total of 3 L per person per day).

Bench Test Results

A burn rate of 3 MSR stoves was tested as well as the time to boil 1 L of room temperature tap water. The wind was calm and the temperature was -2C.

StoveWeight [g]Burn Rate [g/min]1 L Boil Time [min]Stove Condition
Dragon Fly3302.75:40Recently serviced pump and stove
Whisper Lite2772.27:00Well used stove, reasonable condition pump.
Simmer Lite1832.25:30Lightly used stove, reasonable condition pump

  • 590 ml fuel bottle filled with fuel and pump (657 g)
  • White gas fuel density is 0.75-0.785 g/ml
  • MEC boil times are 3.5-4.4 min for the three stoves. I’m going to make the assumption that burn time and burn rate are linearly correlated, so a dirty stove will take longer to boil water, but will burn less fuel per minute resulting in about the same fuel consumption to boil the same amount of water.

Field Test Results

  1. 2 fluid ounces per person per day in the summer and 3 fluid ounces per person per day in the winter. A fluid ounce is ~30 ml or 23 g of fuel. This works out to 120 ml/day for rule 1 and 180 ml/day for rule two.
  2. Used 645 ml for two people for 4 days, 3 nights (215 per pair per night in winter). Cooking involved 2 things of soup, two dinners, three breakfasts and oven baked brownies. All water was obtained via a wood stove. Water was boiled for dishes.
  3. A group of 4 used 4550 ml in 7 nights winter camping (~240 ml/pair/night). All water was from melted snow. Little effort was made to conserve fuel, but temperatures were moderate (-10 to +2C).

Conclusions

Boil time are not a very good indicator of real life fuel consumption as they do not include priming, fuel wastage in fuel lines, wind, faff time, etc. Some are happy consuming snow that is simply melted rather than boiled. Boiling water for purification may take much more fuel. That being sad, bench test results can be used to generate a conservative fuel requirement based on the following assumptions:

  • 10 minutes to boil 1 L of water and 10 minutes to melt 1 L of snow. The longest boil time was 7 minutes, but wind can significantly increase boil times. Therefore a value double that of a serviced stove should be reasonable.
  • 10 ml for priming and wastage (there is always some fuel left over in the stove itself after cooking).
  • A burn rate of 2.7 g/min (equivalent to the burn rate of the cleanest stove and should be the most conservative).

The resulting rules would be:

  1. 120 ml per pair with flowing water (3 L boiled total). Add 35 ml per 1 L of boiled water.
  2. 230 ml per pair on snow (3 L boiled, 3 L melted total). Add 70 ml per 1 L of boiled water from snow.

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