# Winter Garbage **URL:** \ **Category:** Factual Questions\ **Created:** [October 17, 2014, 8:49pm UTC](https://boards.straightdope.com/t/winter-garbage/701617 "2014-10-17T20:49:22Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [October 17, 2014, 8:49pm UTC](https://boards.straightdope.com/t/winter-garbage/701617/1 "2014-10-17T20:49:22Z")
I read, on the usual source, that that sun thing, in its core, produces about as much heat per cubic foot as an active compost heap, so I got to wondering how big a compost heap would I need to keep my 1500sqft, fairly well insulated, single story house warm through the winter (we have rather mild winters here, it usually stays above 10°F but can be in the twenties for weeks on end)? Would it make a difference if we added the unthinkable to it? ---
**Author:** ![flight](https://avatars.discourse-cdn.com/v4/letter/f/bbce88/32.png) [@flight](https://boards.straightdope.com/u/flight)\ **Post date:** [October 17, 2014, 9:16pm UTC](https://boards.straightdope.com/t/winter-garbage/701617/2 "2014-10-17T21:16:22Z")
> [@eschereal](#): > > I read, on the usual source, that that sun thing, in its core, produces about as much heat per cubic foot as an active compost heap, so I got to wondering how big a compost heap would I need to keep my 1500sqft, fairly well insulated, single story house warm through the winter (we have rather mild winters here, it usually stays above 10°F but can be in the twenties for weeks on end)? Would it make a difference if we added the unthinkable to it? How are you doing this? Do you have a big pile of crap in the middle of your house? Do you coat your house in garbage? What kind of windows do you have? ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [October 17, 2014, 9:22pm UTC](https://boards.straightdope.com/t/winter-garbage/701617/3 "2014-10-17T21:22:01Z")
I have storm/double-pane windows and storm doors. I plan to put the compost heap in a large box in the cellar, near the middle of the house (yeah, ok, "single-story may not have been precisely accurate). ---
**Author:** ![Arkcon](https://avatars.discourse-cdn.com/v4/letter/a/96bed5/32.png) [@Arkcon](https://boards.straightdope.com/u/Arkcon)\ **Post date:** [October 17, 2014, 9:32pm UTC](https://boards.straightdope.com/t/winter-garbage/701617/4 "2014-10-17T21:32:38Z")
> [@eschereal](#): > > I read, on the usual source, that that sun thing, in its core, produces about as much heat per cubic foot as an active compost heap, I’m sorry, but what does that statement even mean? The sun is as hot as a compost heap? In the process of fusing hydrogen into helium under gravitational confinement? The same sun who’s surface can vaporize all solids found on Earth? Whatever source gives info like that, I 'd stop quoting it. > [@](#): > > so I got to wondering how big a compost heap would I need to keep my 1500sqft, fairly well insulated, single story house warm through the winter (we have rather mild winters here, it usually stays above 10°F but can be in the twenties for weeks on end)? Would it make a difference if we added the unthinkable to it? Taken by itself, this bit is a little better. But how much heat is in the core of a compost heap? You don’t need to heat your house with the core of the sun, do you? Interesting idea though, you could recirculate solar heating pipes or heat sink pump through a pile of organic mater for a performance boost. ---
**Author:** ![48Willys](https://avatars.discourse-cdn.com/v4/letter/4/db5fbb/32.png) [@48Willys](https://boards.straightdope.com/u/48Willys)\ **Post date:** [October 17, 2014, 10:05pm UTC](https://boards.straightdope.com/t/winter-garbage/701617/5 "2014-10-17T22:05:46Z")
IIRC, The Mother Earth News (TMEN) once had an article about a fellow in Scotland that heated his home with heat from a very large compost pile. The pile was 24 feet in diameter and six feet tall. He ran water through PVC pipes inside the pile. This water was then pumped through hot water radiators in his house. The claim was that a compost heap this size could heat his home for 18 months. His house was about 1200 square foot. I have also read in other “alternative” magazines, that this has been successful in other areas. Building the proper mix for the compost as well as where the piping would go is left to the imagination. Please recall that all of this is IIRC! If one has access to a large quantity of compost, and a fair amount of time, this might be a fun and interesting experiment to preform. Putting the compost heap under the house would not be ideal. I would think that drawing to much heat out of the pile might cause it to slow its digesting of the media, and thus, the heat that one can harvest from it. If I had more time, I believe that I could experiment with this idea to heat my shop. Oh wait, I would have to build said shop first. Hey there is an idea! Now to get the wife on board with this! Wish me luck on this. ---
**Author:** ![Stealth\_Potato](https://avatars.discourse-cdn.com/v4/letter/s/d78d45/32.png) [@Stealth\_Potato](https://boards.straightdope.com/u/Stealth_Potato)\ **Post date:** [October 17, 2014, 10:17pm UTC](https://boards.straightdope.com/t/winter-garbage/701617/6 "2014-10-17T22:17:53Z")
> [@Arkcon](#): > > I’m sorry, but what does that statement even mean? The sun is as hot as a compost heap? In the process of fusing hydrogen into helium under gravitational confinement? The same sun who’s surface can vaporize all solids found on Earth? Whatever source gives info like that, I 'd stop quoting it. Not quite. The temperature of the surface of the sun is a relatively cool 5800K or so, which is comfortably below the boiling point of, say, common metallic tungsten (6203K). And the claim itself is actually perfectly accurate. The sun puts out total power of around 3.8e26 watts, which sounds like a lot, and it is – but its volume is similarly vast, at about 1.4e18 cubic kilometers. So, average heat per volume is (3.8e26 W / 1.4e16 km^3) ~= 27 watts / m^3. 27 watts for a whole cubic meter is fairly pathetic. Consider that a small space heater has to be in the kilowatt range to even keep a medium-sized room warm in a cold climate. A specific figure for the wattage of compost seems difficult to find, but [this page on compost physics](http://compost.css.cornell.edu/physics.html) suggests that a 10+ gallon pile can heat up to 50C in two or three days. If we start with a pile of 1 cubic meter, and assume the compost is about half water by volume, that’s about 500kg of water. At room temperature and standard pressure, water has a specific heat capacity of about 4.2 J/g_K, so raising its temperature by the requisite 30K should require at minimum (30K) \* (4.2 J/g_K) \* (20kg) ~= 63 megajoules of energy. Divide by two days and you get a power of around 365 watts. That actually dwarfs the sun’s average output of 27 watts/cubic meter! Now, that’s just the overall average – and indeed, the heat production is a lot higher in the core. [Wikipedia puts it at 276.5 watts/m^3](http://en.wikipedia.org/wiki/Solar_core#Energy_production). Much better. Still less than compost. ---
**Author:** ![sich\_hinaufwinden](https://avatars.discourse-cdn.com/v4/letter/s/c5a1d2/32.png) [@sich\_hinaufwinden](https://boards.straightdope.com/u/sich_hinaufwinden)\ **Post date:** [October 18, 2014, 1:29am UTC](https://boards.straightdope.com/t/winter-garbage/701617/7 "2014-10-18T01:29:00Z")
> [@Stealth\_Potato](#): > > …If we start with a pile of 1 cubic meter, and assume the compost is about half water by volume, that’s about 500kg of water. Is 50% water by volume a good assumption? I took a quick look at your link and followed a link in it for calculating moisture content and at first glance it seems like they are talking about 50-60% moisture by weight. I don’t believe the table in your link specifies weight vs. volume, but the moisture calculation link in that section seems to be based on weight. Which I think would be quite a bit less than by volume (given the relatively low density of compost I’m thinking of) and would thus affect the power calculation accordingly. Anyhow, I’ve got to head out just now but when I get back I’ll look into it more if you haven’t already set me straight by then. Apologies in advance if I’ve overlooked something simple in my haste. ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [October 18, 2014, 3:02am UTC](https://boards.straightdope.com/t/winter-garbage/701617/8 "2014-10-18T03:02:56Z")
> [@sich\_hinaufwinden](#): > > Is 50% water by volume a good assumption? I suspect it is. That is much lower than most soft-bodied animals and not that far from many plants. And I think a compost heap requires a considerable amount of moisture to decompose well. Not to mention the fact that a dry heap would require _more_ energy to get hot. I guess it looks like the basement idea is not going to do the job. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [October 18, 2014, 9:53am UTC](https://boards.straightdope.com/t/winter-garbage/701617/9 "2014-10-18T09:53:47Z")
The Victorians did it for pineapples: > [@](#): > > The pineapples are grown in a 4ft-deep trench in a 40ft-long ‘pineapple pit’, using traditional Victorian methods; i.e. they are buried under 30 tonnes of manure — and regularly soaked in horse urine. > > Pineapples are usually grown in much hotter climes, so horticulturalists created tropical conditions by heating small greenhouses heated using a chemical reaction between 30 tonnes of manure, urine, and piles of straw. > **[£10,000 for a pineapple! British fruit is world's most expensive (just don't...](https://www.dailymail.co.uk/news/article-2251685/Pineapple-grown-Britain-horse-manure-hailed-worlds-expensive-fruits-worth-10-000.html)** > > The fruit was grown at the Lost Gardens of Heligan in Cornwall, where tropical conditions were created using a mixture of 30 tonnes of manure, urine and straw. ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [October 18, 2014, 11:14am UTC](https://boards.straightdope.com/t/winter-garbage/701617/10 "2014-10-18T11:14:55Z")
> [@eschereal](#): > > I read, on the usual source, Verbal Kint has a website? ---
**Author:** ![sich\_hinaufwinden](https://avatars.discourse-cdn.com/v4/letter/s/c5a1d2/32.png) [@sich\_hinaufwinden](https://boards.straightdope.com/u/sich_hinaufwinden)\ **Post date:** [October 18, 2014, 4:54pm UTC](https://boards.straightdope.com/t/winter-garbage/701617/11 "2014-10-18T16:54:02Z")
> [@sich\_hinaufwinden](#): > > Is 50% water by volume a good assumption? > [@eschereal](#): > > I suspect it is. That is much lower than most soft-bodied animals and not that far from many plants. I think you may have missed the point of my post - that is, whether desirably moist compost is roughly 50% water by weight as opposed to 50% water by volume as claimed. I wasn’t quibbling with the 50% figure itself. As it turns out: > [@](#): > > In the composting industry, the convention is to report moisture content on a wet (or **total weight** ) basis, as the formulas below indicate. > > from here, bolding mine: [Moisture Content - Cornell Composting](http://compost.css.cornell.edu/calc/moisture_content.html) But the density of compost can vary a great deal, depending not just on moisture content, but whether it contains sand/grit in the mix as well. The 5th reply at the following cite claims that a cubic meter of compost can weigh anywhere from 400-1300 kg per cubic meter. ([How heavy is a bag of compost ? in Grow Your Own - Page 1 of 1](http://chat.allotment-garden.org/index.php?topic=52899.0) ) So the 500 kg of water used in **Stealth Potato** ’s calc is not likely to be wildly off, but I think it might be on the high side of what would be in a basement compost heap that had a desirable moisture content and presumably all organic material with no sand/grit. And thus I believe the power estimate was a little high in that regard. On the other had, the calc didn’t take into account any heat loss during the few days the compost would take to warm up from room temp to 50C. Nor did it consider that the rest of the non-water mass (potentially hundreds of kg) has to be heated up as well. Which means the power estimate is probably a bit low for those reasons. In short, I think that different (but still reasonable) assumptions and considerations would yield a power estimates that could be either higher or lower than what was suggested. So it’s probably in the ballpark anyways which is good enough for the purposes of this thread. > [@eschereal](#): > > Not to mention the fact that a dry heap would require _more_ energy to get hot. You appear to be wrong about this, as noted in **Stealth Potato** ’s link: > [@](#): > > …since water has a higher specific heat than most other materials, drier compost mixtures tend to heat up and cool off more quickly than wetter mixtures… > [@eschereal](#): > > I guess it looks like the basement idea is not going to do the job. Agreed. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 18, 2014, 5:29pm UTC](https://boards.straightdope.com/t/winter-garbage/701617/12 "2014-10-18T17:29:44Z")
This has been done for a long time, though I assume heating through another source like a hearth or stove was used in conjunction. It’s still done today, hay and other products will be stored in the basement or crawlspace of a farmhouse and/or piled up against the sides. It works as both insulation and a source of heat as the material is biologically decomposed. To keep a house around 70F through winter is going to take a lot of hay. ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [October 18, 2014, 5:32pm UTC](https://boards.straightdope.com/t/winter-garbage/701617/13 "2014-10-18T17:32:07Z")
60 would be fine with me, I can wear stuff. And I do not like to breathe warm air, 70 might be too warm. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 18, 2014, 5:41pm UTC](https://boards.straightdope.com/t/winter-garbage/701617/14 "2014-10-18T17:41:47Z")
> [@eschereal](#): > > 60 would be fine with me, I can wear stuff. And I do not like to breathe warm air, 70 might be too warm. I’d suggest a sheet metal building over a basement type foundation. Fill the basement and cover the entire structure with compost. The basement fill will provide heat more effieciently since it’s insulated by the ground, but you’ll still need a layer over the whole house that’s several feet thick. Put more active material directly against the floor and walls of the house, and material like hay on outside of that for better insulation. No windows, and doors need to be heavily insulated. You’ll need some vents for fresh air, and I hope you like the smell of rotting vegetation.