# Could a microorganism reproduce so fast that it can be used as a sustainable “burnable” fuel source?

[Repost to condense question down] For a science fiction world of mine I am considering using a type of microscopic organism that is able to generate energy as it goes through its lifecycle, a life cycle so fast that a group of them would be in a constant state of reproducing, decaying, and producing fuel or energy.

So, could a microorganism (bacteria or otherwise) theoretically have a life cycle so fast that it can grow at a rate it can be “burned”? (This is ignoring possible overpopulation and ecological takeover.)

I would provide more details but nothing is really set in stone for my plans with it yet. I just want to try and get a good idea of if something like this is possible.

[Please note I want to stay as close to scientifically plausible as I can, but some creativity is welcome]

Edit: Thank you to everyone who answered, all of the ideas given were great! In the end I chose the one that fit the best into the story! Thank you all again for helping out and for sharing some really interesting ideas!

• Why wouldn’t you just burn whatever the microorganism is eating? Aug 27 '19 at 6:27
• FYI, we provide a convenient edit function below each post: instead of deleting and reposting, just edit the content.
– L.Dutch
Aug 27 '19 at 7:42
• Does it have to be microscopic? Because this is done now with things like corn & sugar cane, or even the wood I use to heat my house in winter. See biofuels for more. Aug 30 '19 at 5:23
• Have any of these answers met your specifications? Have you made any plans with our answers that would impact which answer would be best? Sep 3 '19 at 14:46
• Do you want it to be burning as it is growing, and be hand portable? Because one of those is not possible Sep 3 '19 at 15:35

## 8 Answers

How about instead of burning the organism completely, only its metabolic byproducts can be burned with it?

I have long since thought about alternate biochemistry, but some genius actually created life-like bubbles in the laboratory made of inorganic materials. Those scientists put oxometallate drops on an oil-based substrate, and watched as self-contained environments reproduce into as well as integrate smaller droplets.

Two of such alternatives are silicon and sulfur.

One of the things I read about silicon is that if it's ever used in place of carbon, the silicon analogues of organic compounds will be a lot heavier and more heat-resistant. Moreover, silicon life is problematic because silicon dioxide, which is the equivalent of carbon dioxide, is solid instead of gas at room temperature. You don't want to form silica glass inside your body every time you "exhale".

This leads to the incorporation of sulfur which is a common ingredient in gunpowder, which is then, well, flammable enough.

As for endosymbiont theory, it's a famous theory stating that mitochondria and chloroplasts were once separate cells of their own, until a much larger cell with a much more sophisticated control system lorded over them. The ancient truce resulted in partial indigestion which allowed small cells, when swallowed whole, to be housed inside larger cells while providing resources and without being completely dissolved in enzymes.

Combining these concepts altogether, you get something a little bit like this.

### Pyrokaryotes

A simple illustration of a pyrokaryote (totally made up) that is the result of an inorganic droplet being able to evolve further and gaining the ability to ignite its silicon-dioxide crystalline outer body with every sulfur-silicon-oxometallate metabolic cycle.

It's kind of like a cross between an inorganic eukaryote and a diatom, except that:

• The extracellular matrix will constantly grow and crystallized further if it didn't burn.

• The membrane contains oxometallates instead of carbon-based fats, becoming able to absorb much more heat.

• The cytoplasm which is the hot soup of materials inside the pyrokaryote is oil-based, containing more volatile polar atoms that can cause self-ignition when purged out of the oxometallate membrane.

So there, a semi-organic microorganism that should constantly burn itself if it doesn't want to crystallize towards starvation and fossilize afterwards. Imagine a colony of these, like a chromatic and oily crystal-goo spreading fire as it eats the petri dish.

Aside from the fact that all these are based on speculation, I hope pyrokaryotes satisfied your craving for fire.

• This is actually the PERFECT answer I was looking for! All of the answers given are great, and I especially like the flaming towers idea but this fits into what I was looking for! Sep 4 '19 at 23:54
• @SentiCarter My pleasure. I've been meaning to integrate these flaming creatures into my own stories, but it always gets too technical to be of actual literary use. It's not much but if you need anything, I might have some ideas about an entire ecology of fire-glass-rubber creatures evolved from these, starting from that same pyrokaryote colony becoming a self-burning amber-like crystal once you stopped feeding it. Sep 5 '19 at 1:18

No, I am afraid this is not possible.

Any organism will, directly or indirectly, take energy from the Sun. Thus the first limitation we have is that it cannot use more than the energy flux, which is roughly around 1000 $$W/m^2$$ or lower.

Even if that could be possible, there is the second limitation: mass transport. To grow the organism would need a constant supply of material and removal of waste. That would require a carefully engineered environment to ensure appropriate flow, and it is not going to happen in nature.

Last but not least, if you are able to overcome those two issues, you won't be able to output more than the input you are getting, which are those famous 1000 $$W/m^2$$. You can get more only if you store the produced mass somewhere, and use it all together (this is what we do with fossil fuel).

• True, if this organism evolved on our planet. But what about bio engineered to eat the thermo/warp/necromatic energies on some other planet? Aug 27 '19 at 8:38
• @Nahshonpaz This question has the “science-based” tag. Non-scientific energies are out of scope for an answer. Aug 27 '19 at 9:13
• @MikeScott I’m actually willing to push some boundaries if it could still be plausible. I added the science-fiction tag incase that is needed. Aug 27 '19 at 16:56
• @SentiCarter The science-based tag is “For questions that require answers based on hard science, not magic or pseudo-science,” if you’re accepting magic or pseudo-science answers, you’ll need to remove the tag. Aug 28 '19 at 5:03
• @SentiCarter but keep in mind that edits cannot invalidate existing answers
– L.Dutch
Aug 28 '19 at 6:18

Sure.

Algae are technically protists. They grow very fast, converting CO2 into biomass. Kelp can be burned as fuel.

https://www.theguardian.com/theguardian/2012/nov/14/seaweed-energy-fuel-alternative-1979

Kelp, a prolific grower, increases by about 18 inches a day and can grow to more than 200 feet in only six months. Long used as a source of a valuable compound called alginate (used in ice-cream, soup and strawberry jam to provide the stiffness) kelp has only recently been considered as an energy source.

The "Ocean Farm Project," as the US Navy calls it, is being run in conjunction with Caltech and the American Gas Association. It involves growing the giant California kelp on nets covering a sea area of seven acres. US Navy scuba divers stick small seedlings to the polypropylene nets and the fully grown kelp is harvested by the divers six months later.

The harvested kelp then goes into an airless " digester " where microbes break it down into methane gas which is then burned in a generator to produce electricity. Eventually, it is planned to increase the size of the Ocean Farm Project to an area of 470 square miles. It has been calculated that the resulting harvest could supply the entire natural gas needs of the United States...

Given requisite nutrients, photosynthetic organisms can fix CO2 into reduced carbon very, very fast. Seaweeds are fast but on land canary grass and bamboo can give them a run for their money. I suspect unicellular organisms that do not need to worry about support structures might be faster yet though maybe more difficult to harvest.

There is no reason you could not farm a photosynthetic organism with the intent of later burning it for fuel.

• I think you misunderstood the question. I believe it is asking if the organism could grow so fast that its growth offset the amount consumed by actively being on fire. Aug 27 '19 at 15:00

Certainly.

First, lets consider how long a fire lasts.

A torch lasts an hour to a few hours, depending on the material made. They commonly used pitch or some similar substance that burns slowly.

Second lets consider how fast a slow burning creature might grow.

Bamboo gives an answer- about an inch an hour. Three or four inches is about the size of the head of a torch.

Some hyper efficient bacteria may well be able to grow at a similar rate, producing enough of some pitch like substance that burns slowly to sustain a constant fire. It might use this as a method of breeding.

The bacteria may be a partial hyperthermophile which needs high temperatures of above 80 C to reproduce sexually. As such, it could constantly produce an oil which burns slowly as it replicates sexually, sending tough bacteria spores out to grow elsewhere when it ignites.

Imagine a black goo, slowly expanding. It draws nutrients from the earth, growing taller, forming towers towards the sky. Then, when it reaches a height of sufficient highness, it self ignites, explosive chemical reactions causing the top to ignite. It slowly burns, constantly producing oils, spreading spores far and wide with the powerful flames, the spores using the high temperatures to do rapid sexual reproduction that they cannot do at lower temperatures.

Humans nearby could use such a flame to warm themselves, or cook objects. Certainly, there would be swarms of bacteria around them, but these bacteria only grow at any effective rate on the very rich soils of the land.

• Jolly good, well I'm impressed. +1 Aug 31 '19 at 2:40
• Bamboo is a horrible reference point - it grows fast using insanely specialized techniques such that it can only grow under very specific conditions. Not to mention it needs to spend years clumping to the point where it can do that. And pitch/tar is composed of polycarbon chains - not something that can be rapidly synthesized on the cheap/at all. Sep 3 '19 at 0:44
• We are assuming a plant that continues growing while on fire. I don't think OP is going to deny the use of absurdly specialized techniques, or a few years to grow the base in the ground. Do you have a scientific citation that it's impossible to synthesize polycarbon chains rapidly? Sep 3 '19 at 3:39
• I never said it couldn't be rapidly synthesized, I said it couldn't be done cheaply. And sure, here's one: wou.edu/las/physci/GS361/Energy_From_Fossil_Fuels.htm Petroleum, which is similar to tar (from a chemist's standpoint) has 43.6 kJ (about 10 calories) per gram. The 'at all' is in reference to sustained rapid synthesis. My apologies for being unclear. Sep 3 '19 at 17:17
• Ah well, we can assume a rich world filled with carbon dioxide and nutrients and stuff for growth, along with some specialized enzymes and chemicals that make this more functional. I can imagine that biologically designed pitch made for burning could be made to burn more slowly, giving the thing longer to burn. Sep 3 '19 at 18:31

# Yes but.

Since you have the "science-based" tag, we cannot ignore the laws of thermodynamics. So, your bacteria need an energy source (call it F). They use up this energy, and the available matter, to reproduce and either reform themselves into, or produce as metabolic byproduct, a substance or set of substances containing energy S.

The difference (F-S) has to be positive and is used by the bacteria and re-radiated as low value thermal energy. What part of S is accumulated inside the bacteria and what is oozed out from the bacterial mat is irrelevant.

So far, we only need that S < F. For the bacteria to be useful instead of a competitor in the use of energy, we need for F to be difficult to use, while S can be easily used for fuel.

For example: we have a plant that captures solar energy, as Earth plants do, and build a lignine analogue which is incombustible. It has a high energy yield, but the energy is locked inside and can only be freed by a complicated, endothermic reaction (after which you get an even too energetic exothermic reaction). So, the "wood" of this tree is useless as a fuel. The bacteria, though, can digest and use the high-energy bonds in the neolignine and convert it to fuel.

You can see something vaguely similar with the water-aluminum-gallium reaction. Metallic aluminum has a high energy content, but you cannot get at it and cannot "burn" it (actually you can - that's how you get thermites and thermates. But it's neither easy nor convenient, unless you want a fire hot enough to boil iron). Put aluminum in water, nothing happens because the aluminum is auto-passivating. But mix it with gallium metal, and the resulting amalgam no longer self-passivates: water oxidizes the aluminum developing hydrogen, and if you do it properly, at rates high enough to sustain flame. The bacteria could be your "gallium" to the wood's "aluminum".

The drawback, as you see, is that the bacteria won't produce fuel per se - they will only be able to transform something into fuel. So you need to carry along enough of that something.

The answer is complicated, and highly depend on the interpretation of your question.

If we look at a cell at a fundamental level, everything that happens is chemistry, fire is also equally a chemical reaction. So fundamentally the question could be phrased as "Is it possible for the chemical reaction in a cell to produce a substance faster, than the chemical reaction of fire would destroy said substance. The answer to that question is without a doubt no...

The caveat with the above answer is that is only for an uncontrolled environment. If the environment is controlled in a way so oxygen is limited for the fire, it would burn "slower" (the chemical reaction happens at the same speed of course, but less substance will be converted at a time leading to longer burn time)

A theoretical construct could be made, where a ball on genetically engineered bacteria (they replicate faster) with a fine mesh of artificial blood vessels running through out it to supply it with nutrients, liquids and what else it might need. Fire would only be burning at the surface, but replication of the bacteria happens throughout the while ball. Since volume increases faster than surface area when radius is increased, there should be a certain size where replication of the bacteria can outproduce the loss to fire.

This answer is based on your indication that your 'Science-based' tag is less of a "I want hard facts" and more of a "i'd prefer if it follows hard science, to the extend possible".

The question is very generic. Meaning: if you don't mention which amount of energy you need to produce from fire, the answer is "yes". Basically burning wood is kind of having a form of life (not microorganism, but I'm just writing an example) which takes energy from the sun and then creates a biomass we can burn.

https://en.wikipedia.org/wiki/Biomass

So you are asking if there is any microorganism we can dry and burn. Well, if you don't mind of the quantity of energy, almost all carbon-based organisms will fit, once dry.

Second, you didn't specified the source of energy , meaning where the microorganisms are taking energy to grow. I am assuming the sun, but we can have also environment: there are bacteria producing methane which are degrading dead plants , or manure, and they are very common in swamps. So you have already plenty of microorganism who are able to produce methane (ok, I admit this is not "burning", but they produce something which burns).

To have something similar which burns, you may try some mushrooms. They burn quite good once dry, but you need some external source of material to feed them, since they are Heterotroph.

https://en.wikipedia.org/wiki/Heterotroph

and most of times Saprobiontic

https://en.wikipedia.org/wiki/Saprobiontic

And yes, they grow pretty fast, although we could discuss about "micro".

So the very problem of the "microorganisms" you mention is: where they take energy to grow from, and how much energy you need from burning them?

If the answer is that they decompose some carcass/dead tree or similar, yes, there are many of them, although it could be questioned if burning the original biomass could give better result.

Also bacteria decomposing manure are rowing pretty fast and often produce methane: there are facilities already in use for doing that, in many farms.

https://en.wikipedia.org/wiki/Biogas

Of course then you need lot of manure to feed the microorganisms , which leads again "which source of energy they use to grow": there is no free energy.

## Yes, but it will only make sense if the people are sufficiently low-tech

It is not possible for an organism to produce more energy than it consumes in the first place. If this organism grows through photosynthesis, it will always be more efficient to cut out the middleman and get the energy directly through solar panels.

Unless, of course, the setting is one where the people did not figure out how to collect solar energy. The existence of a cheap, renewable energy source may have something to do with this.

As for the organism itself, there are limits to how fast an organism can grow. However, it is possible that the organism burns very slowly, in which case it may be able to burn continuously.

The problem with this is that the energy released by such a slow combustion process will be very, very small. You're not going to get a lot of heat from this fire - remember, all that is happening is that you are releasing the energy the organism acquired from the sun. It is possible, though, that this organism can grow quickly during the day and provide a little bit of heat at night, releasing the energy it used to grow during the day.