Methane Midden – Learnings

June 2010

The Methane Midden was my first attempt to recreate, on a significantly smaller scale, Jean Pain’s Epic Compost piles that he used to heat everything from his house, to greenhouses, to sheds, and he even buried methane digesters in them.  He worked on these projects for over a decade and did some truly Epic Shit.  The dude was a bad ass and a Bioneer extraordinaire – and he did all of it 40 years ago.   My Methane Midden didn’t produce any capture-able methane.  Why?  I screwed up the PH, screwed up the solids:liquid ratio, and was doing 4 other projects at the time and didn’t focus on it as I should so missed both of the above, or at least failed to address them.  But that is ok, because when you screw up, you reap a boat load of learnings. So it was with me.


  • Spend more than 30 minutes planning a project. A full third of the issues below were foreseeable and I could have caught them.  But that material was decomposing with every minute I delayed, and/or some other guy could have grabbed it.  I struck when the iron was hot.
  • Rubber is a crappy heat exchanger. Duh.
  • Looping hose through a pile haphazardly doesn’t work real well as an efficient heat exchanger.
  • Digging out said looped hose sucks.  Jean Pain figured this out early on, and switched to an elegant solution.  So will I…
  • 540′ (164 m )of garden hose only holds like 40 gallons of water (151 l) , which at 6 glns/min (15 l /min) only keeps the water in the pile for like 7 min. In rubberized tubing.  Yeah, THAT is going to heat up…
  • Rectangles are stupid. The bio-chemical reaction that happens in composting works as a sphere.  Rectangular piles waste 20%+ of the composting material as it never hits prime temp.  ALL of Jean’s piles were cylindrical (ish).  Rectangles… easy to build, crappy in use.
  • Putting large tanks in the middle of the pile screws up the reaction.  Again, the reaction in a compost pile needs about 3′ (1 m) of width (in all directions) to achieve critical mass.  The 2 digesters in the middle of the Methane Midden meant I only had 2′ (60 cm) of compost materials on each side of the digesters.  I thought the straw bales would provide enough insulation to overcome this.  I was wrong.  Jean Pain’s piles were HUGE and over came his buried tanks with shear volume – he had 9′ (3m) of material on each side of the tank – more than enough apparently.
  • Hot Water or Methane.  Choose One… At the size I was building, I would either keep the methane digesters at 100 degrees (38 C) or heat the water to 120.  I couldn’t do both without separate heat exchanging systems.  Jean Pain had 400 meters of  2″ hose (1200′) so his first 100m (300′) went around the digesters to cool them, and then he had 300m  (900′) of exchanger left to heat up.  I can get an exchanger that big in my piles, but not with a digester in the middle.  Hence the L’eau Chaude pile
  • Pine Needles don’t really work. The Methane Midden came into being because some local guy limbed up a huge amount of pine trees – there was no other time I had seen so much “green” brush all at once.  Pine needles have nitrogen, so the pile heated up, but they also have alot of resin in them which ultimately blocks decomposition.   This meant the pile died after 2 months, where I suspect a deciduous based feedstock would have gone for twice that long.   The compost didn’t really finish, ending up as a humusy mulch, for this reason.  I worked with what I had and learned a ton – like I need to source my own material, and also what happens when you pile up 10,000 #’s (4500 kg) of chipped white pine limbs (140 degrees for 2 months, then 100 degrees for another 1, then ambient)
  • Jean Pain style Brush Composting Works. While dismantling the Methane Midden this week I didn’t come across any anaerobic sections, and the pile was still damp.  After 5 months.  Soaking the material for 2+ days adds enough water to sustain the reaction, and the large particle size of the brush provides enough bridging to let air in.  On paper / first glance composting this way is insane.  But IT WORKS.  I still need to figure out the proper C:N ratio – higher on the Carbon side than a traditional hot compost pile to sustain it, but more Nitrogen than the Methane Midden had to keep it going longer.  I ran several smaller experiments over the summer and they tell me that .5-1″ (1-2 cm) trunks of brush with full leaf should be ideal: thicker trunks, say 2″, and the pile die quickly, to thin or brushy (mature lambsquarter) and the pile goes into runaway mode – hitting 178 F (81 C).
  • Green wood is important. It is precharged with moisture, and the sap is sugary.  Bacteria like sugar…  Mixing a pile with dry, dead chips and leaves and you would need far more water –if you can even get enough into the chips- and alot more leaves, leading to matting.  Luckily the vigorous willow strains such as salix dasyclados will put up .75-.875″ rods in one year of coppice growth.  Just sayin.
  • 8 Cu yards of nearly done compost will turn you into a glutton Will explain tomorrow, suffice it to say virtually EVERYTHING in my yard got a 1-2″ (2-5 cm) layer of humus rich mulch!

So, the new Midden is underway.  It will be hot water only, and it will be cylindrical.  It will be made with primarily made from deciduous plants.  There will be no tanks, and I am upping the tubing to 1″ ID.  There will hopefully be as much as 900′ (300 m) of it if I can find some more compost material.  That should increase the volume of water in the pile by a factor of 10.  Also may purchase a new pump that will drop flow rates to under 2gpm, potentially keeping the water in pile for over 2 hours rather than 8 minutes.

Work is happening faster than I can type up posts, though expect a flurry in the coming weeks.  If you want to keep more up to date, I will be updating Facebook more frequently with mini reports.  This is going to be awesome!

Be the Change!


14 Responses

  1. Wow this is awesome, best of luck on the next one. I hope I can someday have something like this as well.

  2. your revealed experience about heat transfer most illuminating.
    Perhaps you should consider , rather than constant flow of water, a pulsed flow to take off peak heat which is most valuable, giving the bugs time to regain their appetite before taking the next harvest of energy.
    A short period of chill should not kill the bacteria and may indeed foster biodiversity of bacteria.
    I view living systems which exhibit homeostasis as being in not so much a steady state of simplicity but rather in a cycle of demand,satisfaction and growth.
    All the above is speculative. Keep on digging. john

    • A pulsed system, in my current design, would add complexity, at least in space heating as it would involve some sort of switch/timer/thermostat. I loathe complexity. A simple way to pulse it would be to upgrade the heat exchanger tubing to “potable water” grade plastic and hook it up so that the cold water intake for the existing hot water heater fed THROUGH the pile before going into the water heating tank. This would take the intake water temp from 52 to 120+ and as long as the system cycled frequently enough, would mean the boiler would never run. My thoughts against this are that: much heat from the pile would be wasted, most of the energy lost from a hot water tank is in standing losses which this wouldn’t solve, and finally there would be no way to space heat. That said, this simple, flow through system is how most compost showers work. As long as you space the showers by enough time you will always have hot water, and you don’t need any pumps. Pile size for a system like this could be much smaller – say 2-3 yards- which has some very real advantages.

  3. *Applause*

    I congratulate you on your efforts thus far and appreciate that you took the time to outline what has and hasn’t worked in your initial trial. It’s sadly rare to see a blogger-experimenter outline what didn’t work, and I know I’m guilty of this myself. So thanks for the progress report and I look forward to the updates.

    • Thanks Kate. Writing about failing is HARD. But in talking with readers this past year, what kept coming up again and again was the Potato Tower debacle. To err is human. Venture Capitalism works on the prospect of funding hundreds of good ideas to find the 1 or 2 that succeed. In my small way I am doing some of that on a micro, ecological scale I guess.

      I also think it is important not to paint too rosy a picture. Like the new midden has already taken 40 hours of work to build. And I’ve only got 2 yards on the pile; harvesting took a week, chipping another 2 days.

      I started the summer with the highest of hopes – those first Methane Midden posts were euphoric! But as July neared August it became clear the pile was dying after 4 weeks, and by the end of August it was clear that I wouldn’t make any methane due to potato harvesting, and life in general. It was very difficult to put that into print without feeling like I let everyone down. Now, with some distance, and the rekindled hope of the L’eau Chaude Midden, I was able to bridge the psychological gap.

      It is important to document this, and failing truly is part of the process. Thanks for your kind words Kate.

  4. I second Kate’s comments. Sometimes I get depressed at all the bloggers for whom things go as planned always. I love to hear about the failures because then I learn too. I learn what works, and doesn’t. I learn another way to think about a subject, another view point. And I relearn things so obvious that I forget to do them- such as really investigating and planning first. I am a good one for just jumping in after hearing a small bit about a good idea. Ooops… thanks for the update and for the future updates

  5. Thanks for taking the time to look up centimeters and Celsius temperatures.

    • You bet Ria. We have readers on 6 continents now, and only half of one understands my numbers otherwise – sorry it took so long for me to do it!

      Plus, we Yanks could do with some minor inconvenience on behalf of the rest of the planet. 🙂

  6. Thanks for taking the time to post all this – the theory and method of what you’re doing, and the results. I’m not planning a methane digester (at this point) but just knowing that someone somewhere has done such a thing and outlined it so clearly is really helpful and inspirational!
    Here in NZ, some of the trees you talk about are unfamiliar; but because you describe so well the optimal materials, it’d be possible to adapt for what’s here.
    I don’t know how you find the time to keep us all apprised of what you’re doing, but sure appreciate that you do! Love the enthusiasm and clarity – thank you!

    • Thanks Annie! I had the pleasure to be in NZ last month and I think several of your invasives would work well in something like this – gorse in particular. We also went to Australia and I was extremely impressed with the growth rates of the eucalypts – messmate in particular: 100 meters in under 100 years! Also, bamboo doesn’t grow well here, but it could be another option for your climate. But in general terms, here is my criteria for “industrial” compost feedstocks. What grows like mad *despite* you trying to eradicate it (gorse)? What trees/shrubs put on 3 meters or more a year? What tree/shrubs will coppice well with minimal maintenance? If its a native or non-invasive, then consider planting a grove. If you are inundated with invasives on your land, or a nearby lot, then use that.

      I see these compost projects as a significant improvement over the traditional burning of cut invasives, as at least you are sequestering carbon and creating a resource (fertile soils).

  7. I was going to comment about how inspiring your undaunted passion is on your blog, Rob, but after reading the comments above, I want to add to the conversation about blogging about failure.

    For me, this connects to the element of our culture that is trained in disposability. “If at first you don’t succeed, drop it and give up” follows closely on the heels of “if you use it and it breaks, throw it out and buy something new.” Most societies in history didn’t have that luxury, hence tinkering, deep thinking, observation, learning, trying, patience, and …. innovation!

    We desperately need innovation right now, along with wide communication about it. We don’t find much innovation in the mainstream world, and those of us trying to do things differently rely heavily on our fellow bloggers, forum commenators, etc, to help us learn from each others’ experiences all over the world. In my mind, this is crucial to building a new culture from the ground (literally!) up.

    As a teacher, I’m always trying to communicate to my students that nobody does things perfectly the first time. Even us professional whatevers spend time crafting and redoing until we are satisfied. But they don’t see that part of things; they only see the “perfect” results, and they often assume they are dumb or that they can’t do something if they can’t get it right the first time. The process of working away at something slowly and patiently over time is not something we are exposed to in our daily lives much anymore.

    So please keep sharing both the successes and the failures. If the doing feels like a compelling, urgent passion, it’s the sharing that will really change the world.

  8. Hi
    Have enjoyed reading posts have just started our own Hotwater Midden on our farm and have just experimented with 50m of 20mm diameter potable water pipe as a coil. Experiment worked now onto a 2000 litre tank buried in a mix of wood chip from deciduous trees and farm yard manure, i.e. cow poo and straw. Will take your tips on critical mass and will get at least 2m of material around tank. I get to move my muck with a tractor and spreader but the compost will go straight out onto our pasture.
    Thanks for the tips.

    United Kingdom

  9. […] 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 […]

  10. Hi Rob,

    Great to see other folks uncovering Pain’s work and experimenting. We are doing the same here in Vermont and would love to collaborate with others. We have expertise in both thermal energy from compost systems and biodigesters. Please look me up if you have the time, it’d be great to hear more about your experience.

    Sam Gorton
    Gund Institute
    University of Vermont

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