Solving problems with indoor compost heater

Guys I've got a fascination with making an indoor compost heater.

What I'm trying to do is solve several issues and see if there's a way to do this.

We collect all our food scraps, and most of it goes out into a compost pile. In the middle of winter, it just sits there though, freezing, only beginning to break down when the warmer times come.

So that is a daily trip outside to empty the food scraps. (problem 1) Our chickens go looking through all this, but most of it, they aren't interested in eating. Chickens are primarily carnivores (problem 2 - we're buying them grains). By the time spring comes around and it's a good time to start growing seedlings indoors, soil outside is still frozen, making it pretty hard to get a medium going for greenhouse plants (problem 3)

I am thinking we could somehow be breeding worms that eat the scraps, and having some excess bugs to feed the chickens instead. Simultaneously making soil while also generating heat inside.

I would like to have a big barrel drum inside the house which is full of straw, food scraps etc. This barrel would produce heat. Obviously though there are a couple unwanted things that are produced by that, but I'm thinking we could come up with ways to capture those bad things and put them to use.

For example a couple of the unwanted things you don't want:

1. smells - possible solutions a) have a compost exhaust, similar to a chimney - bad smells just exit the house b) capture the gasses for a form of fuel
2. bugs breeding and entering the house - possible solution: create a capture for them into a trap to feed chickens
3. anaerobic conditions - possible solution? If it's the right ratio of carbon, nitogren, water and air, does it need to be turned?

What would you imagine is the design for something like this?

If I can't achieve this inside a house, I was thinking it could be a good way to perhaps heat up a chicken coop to give them a bit more warmth. And perhaps some sort of exit where bugs leave, or fall out of a hole or somethnig and smart chickens can eat them as they drop.

For me though, I would love to design and make something that perhaps tied in with the kitchen, sitting maybe next to the kitchen bench or underneath which would radiate heat. I know that now there are thinks like http://www.homebiogas.com/ which converts food scraps into gas for cooking. But what I'm looking at working with people to do is create some sort of open source version of this which doesn't involve keeping this thing outdoors. I've spoken to the guys behind Homebiogas as well and as it stands this thing won't work in cold climates and so it is designed to be outside. By the time spring comes around, we've also produce some soil indoors to help with our seedlings.

anyways, if you have any ideas how it might work would love to hear about it! I know there's lots of reasons why it's a bad idea, but what I want to learn about is how to make those bad things possible opportunities.

Cheers,
Rob

I don't know how breeding insects will come in because ideally I'd like this thing to get as hot as possible, probably meaning no worms would live in there.

Here's what I'm thinking so far, to achieve the main goal of creating heat with it.



I put a cutout in the barrel just to show how the compost would sit on some grates so that excess liquids could drain down, and then be collected for watering indoor plants perhaps.

If I were to pre-mix the compost (straw, goat poo, water, food scraps etc) then fill it up, seal the lid and connect an exhaust to the outside of the house, would this compost stay aerobic and get some warmth generating?

I kept trying to formulate a great response but keep being interrupted. Perhaps there is enough here to keep the conversation going.

I think I was thinking about something like this a couple years ago when I made my first hot composting pile. I was impressed with how hot it could get in the core of the thing around 150 degrees. I like how you are trying to do several things here and truly maximize production. There are several things that you probably already know based on the questions being asked. But my conclusion was at best you would have 2 different systems.

System 1
Heats your home through a large Jean Paine pile (outside) that could supplement your heating needs through providing hot water for the home and maybe through that you could do radiant heat in your floors. This would break down over the winter months and over a few years would provide and excellent growing medium and you could give your birds access to the piles every once in a while to dig and pull out what they could find. It would be a complicated system and could have benefits if managed properly. From what I have seen people that have tried large versions of this spend a whole day or 2 setting it up and then it heats up and works well for just about 2-3 months then the whole piles needs to be turned a bit to keep things nice and aerated. It would be an experiment. Maybe the chickens get access one of those rare

System 2
Indoor vermicomposting and meal-worm composting operation. Though these are really 2 different systems I am pretending it is one. Both animals have wildly different requirements for success. The awesome thing as far as turning food scraps in to soil and chicken food these systems provide in plenty and both wouldn't smell.


Biggest problem with combining them is that temps of 150 degrees tends to kill worms which like it around 70

Love the render. It certainly makes it look nice. Thinking the barrel would need to be steel and not the plastic. My instinct is that you might want in air inlet at the bottom as well. That would help with keeping things as aeorobic as possible if you could get some sort of thermo siphon going on from the bottom up. I would say build something and check it out. It couldn't hurt and it wouldn't take much to set it up either. Might be best for your chicken coop but on the up side you probably have a lot of PREMIXED COMPOST right there. 150 degrees on the inside of the barrel maybe 80 or 90 on the outside? how do you keep the heat just from running out of the exhaust. Mabye more mass on the outside of the barrel to store the heat. Seems like it would be running as a very low temp rocket stove. So build it and let us know.

Thanks, Ryan, for taking the time amongst all the interruptions! I think you're right in splitting it into two systems.

The render looks like it's a plastic drum, but we've got these blue ones here that are painted blue on the exterior. Definitely metal would be the way to go. It's not a huge amount of mass of compost that fits inside a barrel but if the whole barrel did get around 80 - 90 on the outside it would be enough to do something. Maybe not enough to warrant the space it consumes in the house.

I like the outdoor compost idea using radiant heating somehow. I think I would like to do this when we do the next stage of flooring in another building next year.

I was thinking the same about heat exiting exhaust. I'm wondering how little air or how small an exhaust would suffice. The other thing is composting when done right shouldn't smell bad, at least, I don't smell our compost piles outside. So how essential is an exhaust or lid I don't know yet. Then there is the humidity factor.

Only one way to really find out, right? Cheers

One of a few articles in Mother Earth News on Jean Pain compost heating:

http://www.motherearthnews.com/organic-gardening/jean-pain-zmaz80mazraw.aspx

This one is a great introduction and connection to Jean Pain's project and theory. Fascinating and very informative stuff. I've read it several times.

Other articles that I have read and can be searched on google with the following search words "jean pain mother earth news"
These other articles detail the experiments done at the Mother Earth News Ecovillage. These are smaller than Pain's system.

Even smaller and possibly more what you might want, though more contained and inside: https://www.youtube.com/watch?v=-Jm-c9B2_ew

I don't see any reason why you can't just have a large vermicompost in your home and not worry about smells or insects if you feed it right.

Maybe you wouldn't need a fresh air intake if you have a piece of perforated pipe that ran all the way to the bottom. Maybe it has some sort of built in auger so when things start to settle you can crank the auger and get things cooking again. Maybe the auger and the perforated pipe are the same thing. Just ideas.

Scientific method this thing barrels filled with the same batch of premix. Use a Compost thermometer to take core temps and a Infrared thermometer to take outside of the barrel readings. Best to do this in a temperature controlled environment.

Barrel 1 - Control barrel

Barrel 2 - No Lid

Barrel 3 - Lid with central whole like picture


This is the most simple version i could think of but you could easily expand this to cover tons more variables. to see how much air flow is affecting the internal and external temps. My hypothesis is that the open barrel might have toasty core but the outer barrel temps might be really low. So it is about being able to see what amount of air flow is best. Then after you have optimized temps you can move on to how to capture it.

Great article and video Roberto. Thank you for that. It's definitely something to consider down the track creating big piles outdoors and running tubes through it.

Ryan I was wondering if it's going to need to be turned or not to keep up the heat. Perhaps one of these hand ice hole augers could be added people use to make fishing holes. I could be wrong, but looking at this I'm not sure if it would really give it that proper turnover, instead rather just push the compost out from the center. Perhaps tumbling is more the way to go like a lot of people use the barrels horizontally.



Scientific method for sure! I think though for starters since I got barrel already, not a big enough auger like in the render, I'm just going to try one to begin with. Wheel it in and see how it goes. If it loses temp, wheel it out, empty it, mix it up with a pitchfork then bring it back in. That would be a ok prototype. I think then if it did just take the cold edge off a room, even if for a few weeks to a month without turning this would be something I'd like to look at doing more tests on. Surely there's some mixes which are going to burn hotter but not so long, and some materials like wood that will burn longer but take longer to get going initially.

Just sitting on our first rocket mass heater now enjoying the warmth. Hope you guys are enjoying the solstice. Cheers, Rob

i do enjoy the quick renders. What are you using to create those?

Even simpler might just be a perforated pipe that goes down the center. Though that might also decrease core temps.

Hey Rob,

Just so you know (well, as far as I can wrap my brain around this) there is a limit to how much heat can be created from a given amount of compostables. Compost can be turned, yes, to oxygenate the mix and power up the microbes and get another blast of carbon eating frenzy happening... But at some point (I'm not sure when, exactly, but someone more in tune with compost turning as a general and regular practice might be able to tell you---and that question might best be the subject of another thread to gain the right interest...), it's just not going to have any more heat to provide. And then you would have to empty the system and rebuild the compostable mix.

Your keen interest in this is pretty inspiring, as are your cool graphics, but I'm not sure if the project will really be worth the calories you invest in it. I'm not telling you not to do it, but there are simpler ways to get compost heat; Like in that video for instance (which could easily be contained in a box against the house, or actually be indoors-through a big insulated door), if you consider the potential of heating water... I'm just not sure that the radiant potential of the barrel that you are set on as the key element in your design is really gonna be enough to warrant it's construction.

Building another RMH might be a better investment of time and resources.

Like I said, I'm not trying to discourage you, but just trying to give you the alternate perspective of what might be more (or less) worth your time. I think your design might have merit in certain applications, but I think that for it to be effective, it might have to be considerably bigger. I can't tell you for sure.

Ryan's perforated pipe does solve the problem of providing oxygen into the center of the pile (I've seen this done with good effect on a static pile) and this will help keep the microbes busy, but, as with any compost system, you will need to turn the rest to generate multiple heating episodes, and so a horizontal barrel turning system as you mentioned might be more helpful than an internal auger. That said the auger in your sketch could easily have some paddles welded on that extend it's ability to stir barrel load more completely. Some effort would be needed to turn the auger with that much friction on it, though.

Good luck with the project.

These little renders I'm doing with Cinema4D, which is probably overkill for something like this but it's what I started using many years ago when I got into making 3d animations. Cool thing is it doesn't take long for me to get a visual and my mind can pretend it's real before doing anything. also can be detrimental because I have spent copious amounts of time in front of a computer doing creative work like this for the past 17 years

I think you might be right Roberto, about it not putting enough output out for what time goes in. But nevertheless, I'll give it a go. I'm seeing it as a stepping stone for something greater though so is kind of a small scale prototype of something even much weirder I have in mind.

I want to make a cabin down the track which has what I will something like a 'compost core'. It is essentially the engine of the house. You know at the moment the way we all have sewrage, compost and rubbish it's all very disconnected and not really being brought into a large unified decomposer. The idea of this cabin is that it doesn't need a wood fire to be warm it just needs to be fed organic material of different kinds.

We've been using an outhouse for a couple years now, and a couple times per year I empty it out to compost. I notice though in winter there's definitely warmth coming from down below when I use the outhouse I'm starting to think about is ways to hygenically use all this waste to provide a deep thermal heat from underneath the house. So I'm thinking backwards a bit from that, let's just say anything is possible, then in my ideal situation I could just go to a certain drawer and open it up and grab a couple kg's of live worms for the chickens at any time. By the time winter is over, I've got a few tonnes of compost just waiting to be returned to the earth.

Whatever it would be, I would imagine it would be a larger scale version of this barrel. These renders are so simple right now and the idea is so simple.. but I just don't think anywhere near enough thinking in this area has been done. Like obviously when you start thinking of having some sub terrain scale compost engine underneath your house it's a whole other level of complexity. I don't know what sort of thing is capable of turning over that. Not sure that would be feasible at all.

The questions I'm asking is what if it were possible to heat a home with stuff I'm throwing out (our waste)? To me it's interesting that on one hand, I go out into the woods to collect 'fuel' but then at the same time, I take 'fuel' of a different kind (scraps, excrement) I produce inside my house and I take it out to the woods Perhaps not as much fuel going out, but now that I have a rocket mass heater and I'm seeing how little wood I'm using, actually it isn't a huge difference between the ratios of fuel I bring in and fuel I take out. Perhaps we just use wood because we know more about how to combust it? I know wood is really dense so has a lot to release ,more than some food scraps. But no doubt it would be better for the environment if the wood converted into soil instead of exhaust gas. And perhaps we haven't put anywhere near the time into researching compost. I was just thinking, what if we made like the rocket mass heater of compost. I know when I learned about RMH I thought we knew everything there was to know about heating a house with a fire. Anyways, if I then also account for the stuff like cleaning out the chicken coop and goat pens, then suddenly it seems like I could actually have enough fuel. Rather than every week taking 10 wheelbarrows of hay and putting it in a pile out in the open, I could foresee putting it into a door in this engine and somehow mixing it in. Throw in a few new loads of wood chips and things are cookin.

If it could work, then potentially you could have a house that didn't need a wood fire. Then I could chop down even less trees then I do now. And build more soil.

I guess it is very similar to Pain's method, however I am thinking more sort of modular in that it is connected to the house or cabin and wouldn't involve the wrapping of water pipes through a pile. That seems too much effort for what most people are willing to do. I'm trying to think how to make something that people in the future might come to accept as a normal add-on to a house, like a water tank, or a car port. Of course, you have a compost core

A couple weekends ago I immersed myself in microbe talks. I made a playlist of some of the videos that caught my attn https://www.youtube.com/watch?v=FWT_BLVOASI&list=PLHPQN1q72VDzDhFPuGajLG9c-yn2ep6Tption.

Something that I found interesting was that there are (if i recall correctly) 500 million times more bacteria on earth then there are stars.

We've found now bacteria as well that survive in the heat of a blue flame.

With that much bacteria, we haven't even begun to map them all out. Maybe there is a bacteria that can cook a compost hotter and for longer. i.e. get more from the scraps then we thought was previously possible. e.g. They don't just break down the food but then another bacteria works in symbiosis and grab onto the gasses being released and burns them as well. Makes me think of the fungus they found at chernobyl that is chewing up radiation for fuel.

Anyways, maybe it's just getting late and shit is getting really weird Cheers

Your enthusiasm is contagious! There are bacteria that live in molten lava, too, and in glacial ice. Yeah. I dig that stuff too. And yeah, anythings possible in the wild and wonky world of microbes. Who knows what we haven't discovered.

here's an article on passive solar greenhouses and there is a part on using compost to heat it. http://www.lowtechmagazine.com/2015/12/reinventing-the-greenhouse.html

"Compost Heated Greenhouses

Another issue with a solar powered greenhouse is the lack of a CO2-source. In modern greenhouses, operators aim to have a CO2-level at least three times the level outdoors to increase crop yield. This CO2 is produced as a byproduct of the fossil fuel based heating systems inside the greenhouses. However, when no fossil fuels are used, another source of CO2 has to be found. This is not only an issue for solar greenhouses. It's also one of the main reasons why geothermal energy and electric heat pumps are not advancing in the modern glasshouse industry.

In Chinese solar greenhouses, this issue is sometimes solved by the combined raising of produce and animals. Pigs, chickens, and fish all produce CO2 that can be absorbed by the plants, while the plants produce oxygen (and green waste) for the animals. The animals and their manure also contribute to the heating of the structure. Research of such integrated greenhouse systems has shown that the combined production of vegetables, meat, milk, and eggs raises yields quite substantially. [5]

Justin Walker, an American now living in Siberia, is building an integrated system using horses, goats and sheep in a monastery in Siberia. Considering the harsh climate, the structure is partly built below-ground, while its protruding parts are earth-bermed. Above the barn area is a hayloft that provides further winter insulation as well as ventilation in the summer when it is empty. His compost heat recovery system produces hot water that is piped through radiant floor heating zones in the floor of the greenhouse. The CO2 is supplied by the animals. [6]

Heating and CO2-production can also be done without housing animals in the greenhouse. Their manure suffices. As we have seen in the previous article, the use of horse manure for heating small-scale greenhouses dates back several centuries in Europe, and in China it was practised already 2.000 years ago. Since the 1980s, several compost heated greenhouse have been built in the USA. These have shown that a greenhouse can be entirely heated by compost if it is well-insulated, and that the method drastically enriches the CO2-levels in the soil and in the greenhouse air. To add to this, the compost also serves to increase soil fertility. [6]"

Thanks for the kind words Roberto! I didn't know about the lava bacteria.

Heating a greenhouse from compost is what originally got me thinking about the house. It's a bloody awesome idea, isn't it? I saw a video a little while back where they had a greenhouse which looked like a double hoop, so two layers of plastic with just an air layer of insulation between the two.

With a big enough compost mound running down the center it could surely do the job. I hadn't even thought of the extra benefits of c02 production in the air from the compost and how that would benefit plant growth. That is awesome!

This is definitely something I rekon I would be doing before erecting a house around a compost heap Thanks for the information