I am hoping to build a greenhouse this summer or next. It won't be attached to the house and will be in our lawn exposed to elements. Will be oriented east and west lengthwise. So one long side will be on South and the other on the North. I am thinking 8 feet wide and 12 feet long. Is it a good idea to place my compost bins right next to the North side wall? They are pallet bins and I thought they might provide some warmth and wind protection. They are only 4 feet tall so not sure how much wind protection they'll provide. I might be able to plant some shrubs or small trees North of the compost bins.
Also wondering if the North Wall should be greenhouse plastic or should it be solid to help retain heat. The beds will be in the ground with a 2 foot path running down the center. I am hoping to raise worms under the boards of this path to feed my chickens.
Just a idea for you: how about, instead of placing them next to greenhouse, you place them inside the greenhouse?
As in industrial scale greenhouses CO2 is produced with burning things like gas, I find it odd that they dont use compost for producing the additional CO2 to boost plant growth.
You just have to make sure, the compost gets enough oxygen and breaths. I recommend collecting and using a lot of earthworms in compost for that purpose.
I wouldnt use any animal or human wastes in compost inside greenhouse. As they produce a lot of ammonia, so it would not be cool to visit the greenhouse then, so I think this only works with plant waste compost.
With rocket mass heater, I often think to use peltier-elements to produce electricity from the heat.
Here is some topic of that subject if you are interested.
Peltiers are quite cheap about 2 euros per 60 watt (one peltier), but it does not give 60 watts output though, it is just its maximum consumption but it works also opposite way: if the other side is cold and other side is warm, it will produce electricity.
Thanks Henri for the advice and ideas. Unfortunately I do use manure in my compost. It is mainly sheep barnyard waste and our kitchen food scraps mixed, so now I know I can't put it inside greenhouse. I didn't know if the North wall should be a solid wall rather than the greenhouse plastic and throw the compost up against the wall. Maybe there is still danger of it igniting though...
If I wanted to keep it out of the greenhouse and have it up against the North wall, what material would you recommend for an insulated solid wall? Plywood or concrete blocks? Just hoping for ideas. I actually don't think I would have room for the compost pile inside for the size of greenhouse I'm wanting.
I would make it out of whatever you have available. If you are going to buy new, I would probably use concrete blocks to get some thermal mass gain and insulate the outside of them. I wouldn't put the compost directly against the wall if I were doing it because I would be worried about the constant damp compost rotting whatever it was sitting against. If the wall is insulated well, I wouldn't think you would get much heat gain thru it from the compost anyway. Just my thoughts, I'm definitely not an expert.
"People may doubt what you say, but they will believe what you do."
You might want to look up the Biointegrated Farm by Shawn Jadrnicek (sp?). He has long hoop houses and he piles compost up against them for a bit of heat gain. If I remember correctly he has greenhouse plastic on the the North wall but I think he adds a layer of junky plywood outside of the hoops and plastic to better hold back the weight of the compost. He pokes a specific number and size of holes in the wall between the compost and the greenhouse to let in the CO. But he makes a filter to take out the ammonia. He also covers the compost to keep the winter rain/snow from overmoisturizing it.
I think you'd get better heat transfer if you had the thinnest wall between the hot compost and your interior. Old roofing tin may be an ideal material. If you need to use something like cinderblocks, you may want to find a way to let air into the bottom of the block wall so it can rise up the holes in the cinderblocks and shoot up into the interior of the greenhouse. Kind of like a chimney effect in the interior of each stack of blocks. Unless the design requires you to completely cover the tops of the cinder blocks.
I built a compost pile in my greenhouse one winter. It basically made the air of the greenhouse so polluted that I felt like I couldn't safely go into the greenhouse. Since then, all of my compost piles have been outdoor activities.
I personally do not recommend this route... mostly because compost piles often come with bugs, and that easily transfers to your plants. Greenhouses have challenges with pests as is. Adding to that just makes life a lot more difficult. Note that a perfect compost pile at very high temperatures ideally should not attract many insects, but it's hard to get composting perfect. Perhaps there have been successful installations, but I have not seen many. The New Alchemy Institute did quite a bit of research on piles inside the greenhouse in the 1970s, but transitioned away from the idea after having issues with ammonia build up and insects.
Another challenge is that piles generate heat typically (if doing properly) and you don't want heat in your greenhouse all year...
Two methods where I have heard / seen composting working... Creating a "hot bed" -- this is an very old technique where you compost directly in growing beds and use a layer of bio-filter (soil at the top to absorb ammonia). Second, composting outside the greenhouse in the winter...Growing Power does this well because they create very high-heat (ie. low insect) piles and only use them around their hoop houses in the winter. I write a lot about composting as a heating method in the book below if you want to go further, particularly compost heat exchangers (the Jean Paine systems) though those are a bigger investment.
Hope that helps. Just some words of caution I guess.
How about digging deeper than 2' and composting in that sunken path?
So dig down 4 feet,add compost, cover with a soil cap and/or more wood chips.
Add composting worms, but be certain to leave some place for them to hang out that won't get hot.
Shovel the finished stuff into the beds, repeat
Of course one could start the beds as compost piles to begin with.
At my place I make soil by growing in poorly balanced compost piles, essentially raised lasagna hugle beds 😏
with little soil to plant in.
Real compost would make even better bottom layer,I would imagine.
That ammonia is the main problem with compost inside greenhouse and it really does not go away since plants cannot use it directly from air. So you need ventilation, and then you have no benefit from extra CO2 and heat from compost.
Bugs might be a problem still hmm..
Maybe using wood ash with compost, could solve that as it is very high pH and could kill the bugs.
But composting manure inside greenhouse: isnt option, just couse of the ammonia. Composting plant material, is a good idea of proper actions are taken to ensure the aerobic process (which creates heat).
If the composting goes anaerobic, no heat and no CO2 too - but other gases, and bad smell and bugs.
So the best way, as I think it now, would be the aeration of the pile so that the air inside greenhouse rich in O2 would go to the compost.
This you can do with hands of course, but making the big pile move is lots of work and energy.
So it could be something like pipes going inside the pile with little holes, and as air gets warm inside the pipes: it will rise up, and so it will passively change the air inside the pile.
Also a good mechanism could be, that bottom of the compost there is container which allows the liquid from compost to gather.
The liquid is aerated with normal aquarium-pump so the liquid will have good oxygen. Then, once in a while, we just pour the liquid in the top of the compost: so now the whole pile, will get oxygen (hopefully).
And as the liquid again drops to the container, we can aerate it again.
This would be a good way also, to get the right moisture inside the pile: so it wont dry up!
Henri, that was the system I was envisioning for my greenhouse. My current thoughts are to have a compost chamber in the greenhouse that is 8' by 8' by 6' high. At the bottom will be a collection area for juices. Above that will be a 100' long perforated drain pipe in a spiral. That will let air in underneath the pile and be surrounded by gravel. Above that will be a layer of loose pavers or tiles that will let the air rise through them and let me scoop out the finished compost easier. Then the compost pile goes on that. There will be a lid on the chamber so I can make use of the top of the bunker. In the air space above the compost and below the lid will be a fan to periodically draw air through the pile and exhaust it somewhere. My current thought is to run the exhaust in 4" diameter non-perforated drain tiles down the length of some grow beds to give them the heat. Depending on the ammonia in that air stream it may exhaust into the greenhouse or outside.
I figure the bunker will be decently enclosed but probably not air tight. If gasses are a problem I could try to make it more air tight.
I was going to collect the juices and either use them on the plants or have a circulation system to pump them back on top of the compost pile to keep it hydrated
Heat transfer from the pile to the room would be from:
1. 120 degree bunker sitting in the greenhouse will give off a lot of heat
2. I'll make little chimney pipes that come in at the bottom of a side, rise up inside the compost and then poke back out at the top of the side. I'm thinking 4" pvc pipes. This should create some good air currents to send heat farther from the bunker
3. I may run irrigation water lines inside the compost and circulate them around the greenhouse (Jean Pain style). My concern with this is constructing and deconstructing the pile inside a bunker with those pipes in the way.
Jean Pain would get 18 months of heat from his piles that were wood chips and whatever green leaves were on the branches when they were chipped. I only need 6 months of heat so I'd aim my compost mix to be a bit "greener" and hotter than his. I'm thinking 70% wood chips (soft hardwoods like poplar), and the rest something high in N (coffee grounds, grass, weeds, maybe some manure, food scraps). It will take a few years/attempts to get the mix right so that my heat doesn't die off in Feb or keep running strong into July.
I haven't really considered the issue of bugs or fungus causing issues in the greenhouse. I guess I'm just hoping for the best or I'll seal the chamber good enough to take care of it...
Thank you for all the great input. I think I want to stick with Lindsey's recommendation of just keeping the pile outside the greenhouse (for now anyway). I am not sure if I will have greenhouse plastic or a greenhouse kit I buy. Are you saying though to keep the pile next to the greenhouse only in winter because it will be too hot to keep it right next to it in the summer? Greenhouse and compost bin next to it (on North side) would be in shade in summer, but it is hot here in Boise. Should I plan on having a different spot for bins in the summer?
I realize I am late to the discussion and the decision may have been made already. But there is a very informative report about composting inside a greenhouse. The new alchemy institute was working in this back in the 1980s. I found a PDF copy of their report on the builditsolar website.
I would suggest trying to find as many aluminum framed single pain sliding glass doors as you can and building the south wall of the greenhouse with them. If possible get operating ones for the east and west end so that they can be open for the summer. A solid insulated roof sloped to the north with a cement block north wall and a hinged roof that would cover the pallet compost bins against the north wall but can be lifted to fill and empty. The cement block only needs to go as high as the top of the compost bins and framed insulated wall above. I was able to repurpose some shiny aluminum roofing for the inside of the north wall so it reflects back the low winter sun. the solid roof reduces overheating in the summer and the low angle of the sun in winter makes a glazed roof useless. Rather than having in ground beds I have wicking barrels which I can move around. I take out the ones on the north side during the summer and only keep the front row with tomatoes and peppers in there during the summer. This has given me the greates flexibility of use.
As hinted at above you can chip out openings on the inside of the bottom row of cement blocks to allow air to circulate through and pick up heat from the compost on the other side. Later if the system is working for you can upgrade the compost bins with cement block side walls and instal aeration and heat transfer tubes.