I was recently thinking about the human body and the energy we get from food. I understand we don't have the ability to properly digest certain things like stones and wood and grass, but if we did, I was imagining that trees would be a great source of food. I was wondering, how many calories are in a piece of wood, let's say 1 cubic inch, for edibility's sake.

I'm also not sure if the type of wood matters, but if it does, let's say something simple like oak or hemlock, and as dry as the piece would get at room temperature in a normal home.

  • $\begingroup$ engineeringtoolbox.com/wood-biomass-combustion-heat-d_440.html $\endgroup$
    – BowlOfRed
    Aug 14, 2018 at 22:03
  • $\begingroup$ I'm voting to close this question as off-topic because this is not a physics question. $\endgroup$
    – Yashas
    May 11, 2019 at 16:12
  • $\begingroup$ @Yashas if you have feedback about how I can improve this question, please visit this thread: physics.meta.stackexchange.com/questions/11285/… $\endgroup$
    – Erin B
    May 12, 2019 at 17:09
  • $\begingroup$ This question is more about experimentally collected data of a material which isn't well-defined. The answer is different for different types of wood. $\endgroup$
    – Yashas
    May 13, 2019 at 4:32
  • $\begingroup$ @Yashas which is why I specified two types of wood. $\endgroup$
    – Erin B
    May 13, 2019 at 13:04

1 Answer 1


The principle constituent of wood is cellulose.

Cellulose is a complex carbohydrate, made up of the same simple sugars as starch.

The problem is the linkage between the simple sugars in cellulose.

Digestion of complex carbohydrates involves the use of specific digestive enzymes to break specific links. For example, lactase to break the disaccharide lactose into two simple sugars.

Unfortunately, the enzyme cellulase is produced by only a few fortunate fungi, bacteria and snails.https://en.wikipedia.org/wiki/Cellulase

So just treat wood like an equivalent amount of dried mashed potatoes: 4 Calories per gram (answer is case sensitive)

  • $\begingroup$ I was under the impression that it was related by the amount of smoke released when burnt, does this mean that mashed potatoes provide just as much smoke when burnt as wood? $\endgroup$
    – Erin B
    Aug 14, 2018 at 21:20
  • 2
    $\begingroup$ An interesting look at how to "eat" wood and other plant biomass can be found in Denkenberger and Pearce's book "Feeding Everyone No Matter What" en.wikipedia.org/wiki/Feeding_Everyone_No_Matter_What They outline various methods of turning the cellulose into digestible nutrients, mostly using fungi, bacteria and insects. $\endgroup$ Aug 15, 2018 at 7:38
  • 1
    $\begingroup$ @ErinB The amount of smoke isn't important, to know the calories we just need to know the amount of heat produced. See en.wikipedia.org/wiki/Calorimeter FWIW, there's a beautiful but tragic science fiction story named Termites, by Dave Smeeds, which tells the tale of people who have been given genetically engineered gut bacteria so that they can digest cellulose. $\endgroup$
    – PM 2Ring
    May 7, 2019 at 15:07
  • $\begingroup$ @PM2Ring, I suppose that the children of "Termites" really would eat the parents out of house and home. $\endgroup$ Sep 30, 2019 at 19:27

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