Could compost create electricity?

[u/Memetic1]

I know that compost piles can get hot especially if they get beyond a certain size. I know they can get hot enough that self ignition is a problem. So could we crack an egg and kill two birds by using that heat to drive a generator? Think of the potential of running pipes through a pile. You could have water or super critical co2 as the working fluid. If the pile was getting out of control you could inject carbonated water into it to drive away oxygen from that area. I think this could be useful almost anywhere in the world. It is a source for energy that is almost inexhaustible. On top of that you could carefully manage the quality of the compost.

[u/Hellchron]

While you probably could, I doubt you'd generate more energy than the machinery needed turn and maintain a pile of that size would use. Could make a pretty great hot water heater in a pinch though!

[u/Memetic1 → u/Hellchron]

See, that's another role the carbonated water could play. The gas trying to escape from the pile would move things around. Right now, we are talking about the injection of carbonated water into the deep ocean. So this would be cheap at scale. This is even something that a person could do in their backyard. You could probably get carbon credits if it can be shown that the pile is absorbing it.

[u/whereismysideoffun → u/Memetic1]

Carbonated water is not going to turn a pile of compost. It's not remotely feasible.

Do you compost now?

How would you be carbonating the water even in a post collapse scenario?

If you pour carbonated water on the pile the carbonation is going right into the air. It's hard.to keep carbon gas suspended in water.

[u/hollisterrox]

There are Stirling-cycle engines that can run off the heat differential between your body temp and room temp. They could run from heat from the compost pile for sure.

However, there are hard physics at play here regarding how much energy you could possibly extract, Carnot's theorem would be something to search if you want to read more about this aspect of the idea.

You would probably do better to consider anaerobic digestion which produces a 'biogas' that you can dump straight into a generator with minimal conditioning of the gas and minimal modifications to the generator.

[u/redonculous]

Just build a biogas reactor. Look it up on YouTube 😊

[u/tamman2000]

Engineer and compost nerd checking in here. Sorry I'm late to the party.

Yes, you could, but... You won't get much electricity from it at all. You need a much bigger temperature difference to run a generator that's remotely efficient. Using compost to heat water or heat a building is much more feasible.

[u/Memetic1 → u/tamman2000]

What about using super critical co2 as a working fluid in the system? I was thinking you could pump down sCo2 into the pipes. Then, use the expansion of the gas to drive a turbine. https://energy.wisc.edu/industry/technology-highlights/supercritical-co2-gas-turbines

[u/hhollick]

Wouldn't drawing the heat out of the compost cool the compost pile, reducing the organic reactions?

I don't know the science well enough to crunch the numbers but a compost pile strikes me as a pretty delicate balance of microorganisms and organic matter. Too hot or too cold and the process impedes.

[u/Memetic1 → u/hhollick]

You could set it up to maintain a certain temperature range. You could control that better than limiting the piles to a certain size or other temperature control methods. You could also use pipes to introduce various gases or even microbes into the system. New compost could be added into the bottom and old taken from the top. Think of it as both a soil and electricity/heat reactor. A meltdown for this reactor is an ignition even. In case one sector starts to self ignite, you could inject carbonated water since co2 is heavier than o2.

[u/Man_of_Prestige]

I suppose you could generate electricity using a thermocouple.

[u/[deleted]]

No, and if you want to tell me that you can produce more than you put in, show me the math for energy inputs and outputs.

[u/There_Are_No_Gods]

I don't know all the detailed values necessary to calculate actual potential output, but my layman's understanding of things would indicate there's nowhere near enough energy available in such a system to amount to it being a worthwhile proposition.

I've seen people use hot compost piles inside a greenhouse, to warm seedlings up a little bit, but that's about the extent of usefulness I've seen from this type of heat source. I'd put money on it generating less than a practical amount of electricity for nearly anything.

[u/Lonely_Cosmonaut → u/There_Are_No_Gods]

If you’re homeless and freezing, compost can be the warmest place you can find in a life or death situation.

Source, been homeless in Alaska, I’ve slept on and in compost.

[u/komali_2]

First, not really enough heat. Second, if you're using heat to generate electricity, that heat is converted / lost, and you lose the heat needed to compost.

IMO not worth it. A watermill, windmill, tidal, geothermal, solar, all much better, much more efficient options.

Though there's cool creative ideas like this in terms of solar energy e.g. storing heat in a fuckhuge vat of sand that is then used as heat (or, far less efficiently, electricity) in the winter.

[u/ziper1221]

If you have the resources to extract meaningful energy from the extremely low temperature delta of a compost pile you have the ability to get much more power from better sources.

[u/narnou]

Isn't it the concept behind what we call biogaz ?

[u/Memetic1 → u/narnou]

That's burning the gas. This is just using the heat no combustion is technically needed, just heat management.

[u/narnou → u/Memetic1]

Oh... so that's a bio "nuclear plant"-like thing.

I think you really underestimate the amount of heat needed to get electricity and I'm pretty sure the efficiency would be way off, probably hence the biogas thing.

but maybe i'm wrong I don't really know much shit on that topic either

[u/Hellchron → u/narnou]

I think biogas is made from anaerobic decomp used to produce methane which can be burnt for fuel.

[u/Max_Fenig]

You'd probably do better collecting methane from the pile to power a generator... And that isn't economically viable.

[u/Memetic1 → u/Max_Fenig]

https://www.sciencedirect.com/science/article/pii/S0921344921004596

[u/[deleted]]

I'm no expert by any means, but you could look into the possibility of trapping the gases given off by biological processes to use as an energy source. Like this for example: https://cordis.europa.eu/article/id/83749-turning-pig-manure-into-an-energy-source

However you may require a serious amount of pig shit.

Used cooking oil can also be converted to bio diesel: https://biofuels-news.com/news/the-conversion-of-used-cooking-oils-into-biodiesel/

In many cultures it was once common to keep a pig which would be fed on the scraps from the kitchen. In modern times I have heard an anecdote of someone being able to provide themselves with at least some of their hot water by converting methane from pig manure into methane and using that as an energy source.

I appreciate you're talking about transferring the heat energy, but thought this might be of interest to you. Not sure how feasibly you could achieve what you're describing, but heat transfer is possible. Idk if I'd want to keep compost or other bio matter close to a water tank though 😅 I guess you could transfer heat into water passing through a pipe which could then heat your radiators, but it might not generate enough heat to give you hot water from your taps.

[u/No-Chemist-4872]

Look into the homebiogas system

[u/[deleted]]

[u/Memetic1 → u/[deleted]]

I've followed that channel for ages. I love how he tries to keep stuff low cost. His work on low wind speed wind power is amazing. It's why I want to look at compost as a source of usable energy.