Midden L’eau Chaude: The Big Build

Load #2 being dumped for a total of about 17 cu yards (13 cu m). Let's do this.

Last summer I built the Methane Midden which was inspired by Jean Pain’s epic work in 1970 France.    It was big, it was a little insane, and ultimately it didn’t work. Don’t get me wrong – it made a syck amount of compost, but it failed to meet my goals of also producing methane and hot water.  Time to do better.  The second Midden will focus on Hot Water (L’eau Chaude) with a dedicated heat exchanger and will be even larger.  Not only that, but I wanted to learn how much material it truly takes to make one of these so I also sourced all the biomass myself from two local farms, dropping literally hundreds of invasive buckthorn and honeysuckles as well as aggressive “weed” trees such as red mulberry and box elder over a week and then renting a 27hp Vermeer chipper to grind them up.  It was awesome!

This post is pretty epic itself – I opted for smaller photos in the post to keep the overall post length a bit shorter – click on them for a 600×800 shot.   This really should have been 2-3 posts, but I spent more time working than writing.  Skim or read it all the way through at your preference.  Total work covered in the build is 3 weeks, with another 1.5 in the biomass acquisition.  These are “puttering” time lengths – I am always working on 4-10 projects at a time :).

With the material on site it was time to get it soaking.  One of the keys to Jean Pain style brushwood composting is to soak the material for 2+ days to ensure that the chips are saturated to supply the pile with enough water to sustain it for months.  One of the problems I ran into early on is that of scale.  I can only soak about 6 yards of material at a time, which limited me to 1.5 batches a week with my days off and the shorter daylight of Fall.  All told it took over 3 weeks just to soak all the material.

Giant 375 gln (1420 l) totes I bought off of craigslist a few years back for $25 each. Why? Why not!

Once the material was soaking it was time to prep the ground.  I spent a day spreading the old Midden around the gardens.  This was unreal – never before have I had 8+ yards of compost to spread all at once.  EVERYTHING got mulched.  Yes, spreading compost by the wheel barrow load (40 of them!) is as fun as it sounds.  I will say it again and again – COMPOST is the true point of the Middens – gathering energy from them is merely function stacking an intrinsically useful activity.

As this pile was going to be 50% larger I had some concerns about it breathing well.  At one point I had myself talked into laying out 4″ perforated drain tile for air circulation, but thought better of it for several reasons.

Cupplant, Sunchoke, and Sunflower stalks forming the passive air circulating foundation to the Midden. After the winter it turns into humus and sequesters carbon. Regenerative waste stream? Check.

First – it added expense and resources.  I like to keep the plastic to a minimum; while not afraid to use energy or resources for the Greater Good, I also like to use natural products whenever its feasible.  Second, Jean Pain never did so I’m not even sure its necessary.  My solution was simple – I cut down a half dozen Cupplants that were nearby in the prairie garden that serves a insectary habitat near my permaculture guilds.  The thought is that these will allow air to come in slowly from the under the pile as they decompose themselves.  Basically the same reason you are often told to put twigs under a normal passive compost pile.

Now, the observant amongst you will notice a piece of .5″ conduit stuck in the ground with a tape measure  in front of it.   Of course there is a very good reason for this.  The Midden LC will have a 3′ (1 M) diameter core of brushwood that will be wrapped with 1″ tubing, but I am getting a bit ahead of myself.    With the base down, it was time to get building.

The Core

The core diameter of 3′ was chosen for the simple reason that hot composting seems to benefit from a minimum dimension of at least a meter.  Build a pile smaller than this, and you won’t get hot enough.   One of the downfalls of the Methane Midden is that the layout forced a width of only 2′ in most cases.  I thought that the straw bales insulation would be enough.  I was wrong.  Back to basics then.  Getting wood chips to form a cylinder can take some doing.  Luckily I had enough 2′ garden fencing in the garage to make a “mold”.  The thought was to cut the fencing to the circumference of a 3′ diameter circle.  Time for fun with math!

4' (1.2 m) tall Core. As I unwrapped the fencing, I would wind 150' (45 m) or so tubing around the chips to keep them in place.

A circle’s circumference is Pi x the Diameter of a circle; 3.14 x 3′ = about 9.5′.  Done.   Now, when you cut the fencing – leave the “nubbins” on the cuts – this works well to fold around once you get the circle made – think giant velcro.  The conduit I stuck in at ground zero and measured 18″ off each side to center the core column.  Then it was simply a matter of schlepping in the soaked chips.  About every 8″ (22 cm) or so I tamped the chips well with a 12# (5kg) sledge hammer.  Once I had 2′ tamped in place, I unhooked the fencing and unwound it.  Thanks to the tamping, the chips stay in place very well.  I then wrapped the fencing on the top of the cylinder with about 2″ (5 cm) of overlap on the bottom.  Then I started wrapping the heat exchanger around.

I love this shot. It really shows how stable the chips are with tamping (walking on it at this point). Jean Pain didn't use molds, just slapped it all in place with a pitchfork and walked on it.

This progressed 2 times until the core got about 5′ tall.  At this point I was becoming somewhat concerned that the column could topple, despite how stable it seemed.  Redoing it at this point would SUCK, so I opted to switch gears and work on the outer “donut” of biomass.  The thought here was to again use the 1 meter width of material to maximize the bio-reaction of the thermophilic bacteria.  Having 3′ of material on each side of the exchanger giving the Midden L’eau Chaude a total diameter of a bit over 9′ (2.75 m).  The other important reason to start building out the “donut” was that stacking, and especially tamping, the Core was getting difficult as it was over shoulder height for me at this point.  With a 2′ tall rim around the Core I could bring it up to its goal of 6’+ bringing the total heat exchanger length to over 550′ (168 m).  The heat exchanger needs a bit of explaining since it is critical to the Midden, so here goes.

The Heat Exchanger

550′ (168 m) of 1″ (2.5 cm) polyethylene irrigation tubing. Never one to be modest… this is a work of art.

This is the finished heat exchanger and I won’t even try to be modest.  It’s GORGEOUS!.  The water will come in the bottom, spiral up for 6′ and then take two larger loops back down to exit the pile.  Why this way?  It has a lot to do with temperature gradients.  Heat transfers best the larger the temperature differential (delta T).  The final goal is to that the water entering the pile at about 80 F (26 C) and exiting north of 120 F (49 C).  The bottom of these piles are cooler (heat rises!), but will still be rather warm.  As the water in the exchanger warms it is also climbing up through the pile, which is also getting hotter.  The thought is that there will always be a delta T of 20+ degrees between the pile and the water in the tubing.  Slick, huh?  Now wth is up with the big looping spirals?  The poly tubing kinks somewhat easily, so I chose to take 2 revolutions to expand the diameter of the spirals and slowly increase the degree of bend up to my final exit point. Now some final thoughts on the exchanger.  First, I would shift the hole thing up a foot.  Starting 4″ from ground level like I did will not add much heat to the water, whereas there is over a foot above the top of this column now that I am done.  I had thought that the top would be cooler, but that is not the case – no matter how much I pile on the heat just comes right through it: put your exchanger to within 6″ of the top without fear as long as the pile is hot.  Can you see I am already planning Midden #3?  But for now we need to bury that exchanger. Fleshing out the Midden


Taking shape! This is about 12 cu yards ( 8 cu m) with a current height of 5.5′ (1.7 m) and a 9′ (2.7 m) diameter. Awesome.

To keep the pile nice a tidy, and also to ensure that I could still walk around it, I again used a garden fence mold for the 9′ (2.7 m) diameter “donut”.  this time I opted for 3′ tall fencing.  The outer section takes an immense amount of material to fill – it was almost 2 weeks to get it to this point as the pile at this point was over 12 cu yards and weighed over 6 tons due to the sopping wet chips.  Remember that I could only do 5-6 yards at a time as the chips had to soak for several days.


I had intended to unwrap and re-wrap the fencing again, but in the end chose to leave it on and switch again to an insulating rim of straw, which I ended up stacking 3 tiers high.  It gets significantly colder here in southern Wisconsin than in Jean Pain Provence with winter lows dropping to -15 (-26) at least once or twice.  Time to break out the dump truck again!  Back to Craigslist and I contacted a farmer about 4 miles away with 70 bales of Oat Straw.  I would need about half that for the Midden, but filled up the truck to mulch the beds as well.

BART holds 48 bales of straw. I am not saying *everyone* needs a dump truck. But in my case I am making a good argument..

With the straw in place around the fencing, I then stacked a third tier of straw to form the mold for the final several yards of material.  In the shot at right the pile is nearing 7′ (2.1 m) tall which was the goal.  At this point I was nearing the end of the biomass and began to focus on rounding out the pile and maintaining the 3′ length from the heat exchanger as much as possible.   Was incredibly pleased with how the Midden was literally shaping up.  Sometimes a project just CLICKS.  This was one of those!

Gap left for the pump installation. You can FEEL the heat coming from the pile, the core of which is 150+ (66 C) at this point. Dang sucka.

Jean with one of his piles. As you can see his heat exchanger loops would have gone around the OUTSIDE of mine. Then again his piles crested 80 tons - 10x as big as mine. Jean was a visionary, and I am honored to be able to promote his work for a new generation.

The pile rounded out at about 17 total yards of material, and final dimensions, with straw are about 7′ (2.1 m) tall and 12′ (3.6 m) wide.  Its BIG.  With the cooler temps, the midden now steams almost 24 hours a day – silent testament to the incredible powers working within.  Nature truly is awesome.

Next installment will be to hook up the pump and see what this baby will do.  Stay tuned!

Be the Change.



31 Responses

  1. Very impressive. Have you considered looking for copper coils – much better heat transfer than plastic.

    • Or even aluminum or iron. Copper tubing would be $1500 vs. the $80 for the plastic. That is far more than my VERY indulgent family is going to permit coming from the budget for an unproven system. If the experiments come out positive, who knows?!

  2. Hey rob, awesome to see this thing finally built. Can’t wait to see all the numbers as the water starts heating up, especially as the temperature keeps dropping here in Wisconsin.
    I was wondering if you have ever contacted Jack Spirko at the Survival Podcast. It is a large community that would love to hear the stuff you are doing. Jack does many shows on permaculture and alternative energy ideas. I tried emailing him to contact you, but don’t know if he ever got the message or got a hold of you.
    Good luck with the projects, I love hearing about them.

    • Thanks! I haven’t heard from him, but once I have this fired up I may reach out to him. It was really cool to have Build It Solar and Hack A Day pick up the Methane Midden. The more people that get inspired to try something Epic, the better for us all!

  3. I didn’t realize it would lock together so well, due to tamping.

    Are you going to try planting something on the inside edge of the straw bales?


    • Thanks Joel. Still need to figure out a small technical issue with the pump (posts are lagging 1-2 weeks behind reality), but massive progress for sure.

      The angle of repose of wood chips is quite tall to begin with, and once wet the static friction goes up even more. Look at Jean’s piles – he loose stacked those with pitchforks and climbed on top with ladders. The wire fencing and straw bales are only necessary because I was limited on biomass and space – I couldn’t afford to waste either.

      No planting on this one until the New Year (if its still hot) due to day length. We are already barely at 12 hours, under that day length most plants shut down growth regardless of heat.

      What is VERY interesting is that I tomato seedlings sprouting between the protective slats of one of the piles I built in early October. They are still green and vibrant (though not growing) despite nightly lows under 0 C and several freezes to -3 C. Most plants sprout due to temp, but grow due to light.

  4. Every post I’ve ever read involving failures with “The Jean Pain Method”, and there have been several, have been due to the compost heaps being either – under-sized – not enough moisture content &/or, the wood chips have not been shredded properly. In most all instances, it’s been due to the combination of the three steps listed above.
    The Pain’s make it clear in thier book, that there can be little alteration from the method described if you wish to achieve success with producing the desired heat & methane production Jean achieves.
    I just love the book! His methods are ideal for people owning large acreage or who access to this type of land, to accomplish self-sufficiency or at least, better self-reliance while helping to protect that land.

    • Russ – thanks for your comment. Of course I’ve read his book, and watched all the videos I could find. I certainly agree that his methods are fantastic and work well for all those people with 500+ acres of woodland to maintain. But my take on his “methods” was broader. Jean took the problems that were facing his age and worked to solve them with the materials he had at hand, using the science and engineering he could gather and master himself.

      It is readily apparent that the piles can’t be as large as Jean’s in Suburbia, but that certainly doesn’t mean that we shouldn’t try to achieve something better. If you’ve read through this blog much at all, you see that it is focused on improving the sustainability of the suburbs, specifically by producing more food in small spaces. One of the many things that have caused Jean to become a mentor is our similar personalities, combined with our similar paths. Jean started with compost first – because without rich soil little is possible. It was only after years of making compost that he spent a decade perfecting his method of “function stacking” hot water and methane production onto the composting. I am doing the same – the amount of compost needed to turn a lawn in to a productive food-scape is staggering –I import 20,000#’s of biomass a year. While I almost certainly won’t ever be able to keep a pile hot for 18 months, nor be able to produce methane AND hot water off of one system, I know I can pull some heat from the piles, and methane production using compost heat is very feasible. In the words of my friend Patrick – ANY BTU you add to your home is an offset – whether it is 100,000 or 10,000,000.

      Jean is an inspiration in many ways. To your point – I have solved the water problem, I am close to solving the shredding problem, and the size issue can be gotten around by adjusting the end goals to match reality. In today’s culture of prepackaged everything, the most revolutionary act may be in simple DOING rather than in achieving.

  5. Have you given thought to heat loss down into the subsoil?
    It would be nice to have temperature measured either centrally under base or at the perimeter( drive a steel pipe under pile at an angle down into the soil ) and either borrow a thermocouple or, simplest, install a hairpin loop of small bore tubing, fill with water, and withdraw the subsoil temperature sample at weekly intervals.
    Me, I would have put an air insulating cell at the base, say two layers of timber pallets , sealed with straw.
    The heat loss calculation can be done by any architect or civil engineer.

    The quality, ie useful temperature times volume of hot water produced will depend upon the rate of extraction eg the pump flow rate. The core temperature will affect the microbial action, for instance a sustained high temp. will sterilise the compost and might even start a smouldering fire.
    The reason for this is that alcohols and ketones are naturally produced by the brewing of sugars, and the fun begins when the temperature comes close to the combustion point of these volatiles. If the pile is disturbed and air gets in it is very difficult to quench the fire.

    • John, yep – strongly considered putting down 2″ foam board, but visualizing the resulting sloppy anaerobic mess from the undrained seepings shot that idea. Not sure I will ever go to the lengths you state, but virtually all the heat would be trapped if the pile were situated in a Hoop House, which I still feel is the ideal spot for one of these.

      Do you have any links on the science of hay barn fires? I try to keep my piles under 155 F (68 C) for all the reasons you say (mostly the microbial ones), but I’d love to learn more about what happens on the extreme end.

      Pump rate is a major consideration, and one of the reasons I opted for a 3spd, dual wound Grunsfor pump which will allow me to toy with 2, 6, or 8 gpm rates without a reo-stat.

      There is about a 4-6″ ayer of cupplant stalks, and large twiggy branches which was installed to allow the pile to breathe, but will also likely accomplish a similar goal as your straw packed pallet idea — which sounds awesome, simple, and elegant btw, thanks for that.

  6. Man, I am very serious about my compost, and that pile is a thing of beauty. Plus, your wife is obviously a good sport. Great work and thanks for sharing!

  7. Do you ever get tired with the chorus of “awesome”? I’m so consistently impressed by all that you do, Rob, that I’m willing to go on sounding like a broken record. Impressive as ever, and as usual, I look forward to reading more.

    • Um, no? 🙂

      Seriously though I get concerned that people don’t think that they can do this too. I’m a “regular guy” 5 years ago I knew almost nothing about this stuff, 7 years ago I had never gardened. Figure the amount of brain capacity and energy that the average American puts into sports and television and rechannel that into, well, what I do. That is the biggest difference: focus. But trust me I play plenty of video games and read fiction too.

      • >Figure the amount of brain capacity and energy that the average American puts into sports and television

        Clay Shirky wrote a book called “Cognitive Surplus” about this. I only read the first couple pages, but it’s kind of amazing.

        He talks about projects like Wikipedia, but I think cob ovens, earth-sheltered homes, and compost-heated greenhouses are among the most important technologies to develop.

  8. Wow. Wow, WOW! I am so excited to follow this project. You amaze me, as usual. We are two years (hopefully!) away from getting back to the land and I am putting a Midden at the top of my list. I’m looking for Jean Pain’s book but can’t find it locally (we’re in the Middle East). I would love to be doing my homework while we’re over here so I can hit the ground running when we return. What you’re doing is absolutely helpful and, well, inspiring. Thank you!

  9. Rob – fantastic work. I have to ask what your neighbors think about this scale of activity? I ask b/c I had to help a friend transport raised beds to another guy’s house with my truck over the weekend b/c the neighbors, after receiving free organic veggies all summer, freaked out at the sight of row covers and demanded the beds be removed (Nazi HOA rules). Also, I emailed you my potato bucket 2010 results – have you had a chance to review them?

    Keep up the inspiring work!


  10. That is an impressive project.

    Are yo concerned about it getting too hot or does the moisture ensure it stays just right? After one of our compost piles caught on fire I have a healthy respect for their heat potential.

    • Thanks. Not nearly enough nitrogen for it to do so – the one I build in the spring, which will have far more green material from the more leafy brush, will be more of an concern (I hope!), but yes, the extreme moisture and humidity should mitigate the combustion potential. *should*/

  11. straight gangsta. keep it real.

    -pecan, atl, dirty south

  12. http://www.psla.umd.edu/extension/publications/haycombustionp1c.pdf
    is a good description of how fire develops, not at the centre, but at the wet/ dry interface, I suppose this is most likely to be at the straw jacket .
    Keep an eye on this by poking in a metal rod like a roasting thermometer.

    If it does smoulder, try injecting a lot of cold water before attempting to expose the source of smoke.
    Don`t worry. Be happy. john

  13. Just wanted to add a great site. Ijust stumbled on it a few weeks ago. You have def giving me some ideas in my head. We are building a passive solar house 1.5 years in) and I will have these solar boxes 8′ x 9′ (yet to be determined ,or rather what we can scrounge) to preheat water, I was allready using 2″ poly tube and was just going to use the sun BUT these pits could also have composted biomass as well, which would allow heated showers in morning etc.. thanks for the ideas and keep up the great work.


  14. We just built our pile at the beginning of the week. We have a pto chipper so we are trying it to do it with chips instead of shredding it this first go. I mixed in some fresh manure to the central pillar to hopefully give the chips a jump start. We guessed that the start up time would be a bit slower but if we could get it starting to heat up it would be okay in the long run. We ended up with about 22 yards of chips/sawdust/manure. In the pile. We are going to use it as a closed loop space heater. In the spring we plan on making a larger pile and put a digester in it.

  15. […] News happened to have an article this issue about using wood chips in your garden, and of course Rob over at One Straw has found a fabulous use for them in his Midden style compost systems. So I am using ideas from both. The first batch went to renewing the paths in advance of the coming […]

  16. […] so I was very excited to discover someone that had found success with it! Also check out his Midden L’eau Chaude for producing massive quantities of hot water and compost, and his articles on Sub-Acre […]

  17. I wanted to say that I love this so much. With any luck, in two weeks I will be the proud owner of a .5 acre lot with modest house in Texas, and I have to say I looooove the thought of buuilding a big ass Midden like that, and connecting it to an underfloor radiant heat system. The house is on pier and beam, so there’s a good chance I can do that relatively inexpensively, and then save big bucks on winter utilitty bills and end up with, as you say, a syck amount of beautiful compost.

    I’m thinking of just asking the local tree trimming services to dump their chips here, but I’m worried about bringing in disease- the lot already has some beautiful pecan trees that fruit delicious nuts (the house was built in 1959, so someone put the thought into planting food trees a long time ago for me- it’s just a matter of finishing up the job!)

    When I talked to the owner today she said the soil there is like chocolate cake. It’s been all organic for as long as the house has been around, we think- and there’s a large firefly population in the neighborhood because very few people, if anyone, sprays in the neighborhood.

    I’m up at 3:00 in the morning because I can’t sleep, I’m too busy hoping that I can build one of these monsters in my yard in the next few weeks. 😀

  18. I’ve been around the site for a few weeks I finally got to this posting.

    While I found “The Jean Pain Method” a number of years back at this point I have not done anything trying it. However,,,,,,

    A year ago I jumped into the idea of using a high tunnel here to increase production on my fledgling truck garden endeavor (to include winter harvesting/growing in my zone 3b/4a). The first of these will include an enclosed “midden” and in- soil PEX pipe for ground heat. I’ve conferred with a number of growers around the country that use the soil heat with great success but are still tied to standard fuels for the source of heat. Although a few are investigating compost heat with various ideas.

    Of course I smiled big time when I read your comment about capturing all the heat the pile generates while enclosing it in a hoop house (like minds and all) I have been working out the future bugs on paper and researching the possible negatives. One concern is the excess moisture the pile will generate, this might be alleviated with circulation fans. Another is how large of a pile I will need to make a significant impact on the actual required BTU load over 4-5 months. One thought is making a stand alone hoop in close proximity to the tunnel containing the midden, then circulate the warm air as well as the heated liquid back to the growing tunnel, at least the first year to get a reading on how this will work. Hopefully I can glean more info from your project over the next few months.

    Great work!!!!!

    Did I mention I live at the northernmost end of WI where it really IS cold in the winter? heh heh

  19. hi onestraw
    hows it running a couple of months on
    any calculations of heat production yet
    looks absolutely, brilliant but haven’t actually found anyone who has managed to keep one running for anything like jean pain’s 18 months. do you know of any

    • Xplode. Thanks for the comment. Mine died early due to not enough nitrogen and my venting the heat into the open air for a week. Basically I had upgraded the heat sink to a 55 gallon drum from a 15 gallon one which had been maintaining 101 F after a month. The 55 gallon drum was uninsulated and exposed to the ambient air (November in Wisconsin). I then got a nasty cold, had some family events and Thanksgiving which meant that I didn’t get out to check it again for almost a week – and in that time frame the air temps had dropped to under 20 F at night. Essentially I killed the pile by dumping so much heat through the sink (barrel) into the atmosphere that the internal pile temp dropped to below the mesophillic bacteria threshold at about 63 degrees when I got to it again. Without the environment favoring the mesophilic bacteria the piles temps began a slow spiral and I disconnected the pump systems after a few days to prevent them freezing.

      I owe everyone a post with more details and learnings. The long and short. Piles need to have more nitrogen – brushwood size should be .75″ and smaller limbs in full leaf. While I didn’t get as good of calculations as I wanted, I was not impressed with the recharge rate of the pile. Looking at the heat exchanger from Jean – he left much more space than I did between his tubing. In a pile this size –if it is even big enough– 30% less tubing might achieve the same result. I see compost heat to be more useful for maintaining temps – say of tilapia or methane tanks in a hoop house overwinter with active heat being supplied by solar thermal or biomass. I assume Jean had reached the same conclusions – his piles were primarily for methane production and he was mostly using the hot water to heat his house, but from an engineering standpoint he was using his house as a heat sink to cool the water enough to bring the methane tanks temp down. I.e. there are more efficient ways to heat water, but surrounding a methane digester in 8′ of compost not only insulates it, but also meets all its BTU needs while supplying you with awesome compost in the spring. Same could be said of an aquaponic system – a 5’x5’x “X” length tank surrounded on all side by a 6′ windrow of active compost would cut your heating costs to only whatever heat was lost through the vertical plain while also adding *some* –but not all– btu’s for the tank. Primary heat would be supplied by solar thermal or biomass or even a heating element on a wind turbine, but that is a really expensive way to make heat.

      hope this helps. Feel free to shoot me an email at one.straw.rob (at) gmail.com

  20. Glad to learn of you and your activities. I’m new to Madison, but not biogas technology.I’d love to learn more about you, your project and its application. I have built many successfully operating units, but this is the darnedest thing I’ve ever seen! Keep up the good work.

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