In the question of a biological cannon How would a Biological Cannon work? , one option was to use biological by-products for chemical propulsion of the cannon ball. It might have also been propelled by a non-chemically reacting high pressure gas or fluid.

We can do all sorts of simple chemistry with biological materials, and get new compounds; for example using burnt wood ash to create lye. When yeast ferments fruit to create alcohol, there is an upper limit to the percentage of alcohol (15% to 25%, according to the good folks on the Alcohol Stack Exchange: https://alcohol.stackexchange.com/questions/110/what-is-the-highest-alcohol-content-achievable-through-brewing#120). If we distill the alcohol, of course, we can some decent fuel. The creation of lye and higher proof alcohols, however, requires a bit more human intervention.

The bombardier beetle produces two chemicals that when combined, have a violent reaction. What material combinations (from anywhere in the animal and plant kingdom), without processing (other than harvesting it), could also give such reactions, and what might those theoretical limits be? Would these materials come from simpler organisms (yeast produces alcohol) or from more complex ones (bees creating honey)?

My initial guess is that creatures in the same environment wouldn't generate byproducts that would cause energetic reactions; you'd have to be clever and use animals or plants from different parts of the biosphere. But perhaps, there might be a combination of plants/animals that did things like create the equivalent of forest fires in a world devoid of lightning, perhaps.


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Introducing the amazing Diesel Tree, Copaifera langsdorffii, a medium-sized tree native of the South American rainforest, usually reaching 12 m (39 ft) in height; the tree produces a combustible oil which can be used as biodiesel; the oil is extracted by tapping the tree in a similar way as for the extraction of natural latex.

*Copaifera langsdorffii* in a park in São Paulo Brazil.

Copaifera langsdorffii in a park in São Paulo Brazil. Photograph by Mauroguanandi available on Wikimedia; public domain.

Wikipedia says that

The diesel tree can be tapped every six months for more than 20 L (5.3 US gallons) of fuel, and it will continue producing for around 70 years. One acre with around 100 mature (15-20+ years old) trees would produce up to 25 barrels of diesel per year.

From another source ("The Diesel Tree: Grow Your Own Oil", by Warren McLaren, April 2008, on Treehugger):

"Once filtered—no complex refining required, apparently—[the oil] can be placed straight into a diesel tractor or truck, [...] with the only negative being that its particular form of diesel needs to be used within three months of extraction."

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    $\begingroup$ This tree and its genetically enhanced offshoots might make a 'cannon tree' far more feasible than I would have ever imagined! So the energy density of a tree's output is far higher than I would have guessed, on the order of 30+ MJ/liter. I wonder if any natural fertilizers, if added, would make the equivalent of a fuel oil/fertilizer explosive, which could be used in the cannon question. $\endgroup$
    – asylumax
    Commented Dec 19, 2017 at 4:06
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    $\begingroup$ Given that the oil is made out of Terpene, it's now only a little step to turn the oil into a big kaboom. Find something that cracks it down to its monomer size, pout it on something like a sponge that highers the reaction surface, and finally, if that still isn't explosive enough, heat the fuel. You'll be left with an explosive, gaseous atmosphere inside the barrel that should have no problem to keep up against historical cannons. $\endgroup$
    – Sudix
    Commented Dec 19, 2017 at 11:09

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