Methane Midden – La Fin


The Methane Midden got a ton of press for its attempt to produce energy from brush.  And in a suburban backyard no less.  But as I spent the day Tuesday finishing its tear down I was struck by the need to set something straight.  While the goal of the experiment was to try to produce methane (and hot water in the new Midden), the goal of the system is, and will always be, to make an insane amount of compost.  I routinely trailer in over 10 tons of organic matter, mostly woodchips, each year to my .5 acre ( .2 HA) lot and my soils are still far from done.   Our urban soils are incredibly denuded in most cases, and until the organic matter content gets up to 5%+ in the top 6″ of soil we have a ton of work to do.  And in this region, topsoils used to be 6-10 FEET thick (2-3 m).  To add 1″ of compost on even .1 acre you need 13 yards of compost.  It is mind numbing to think about how much compost and mulch we need to heal the soil of our cities.  Luckily all the carbon we need is unhappily sitting above us in the atmosphere.  Hence my desire to cut down coppice and compost it.  Putting our tea bags in a bin won’t cut it.  The fact that I am working to get energy out of the piles is a fringe benifit.  A really, really cool one.🙂

The break down of the midden was not sexy, but it was awesome none the less – 8 yards of compost, all at once, is simply staggering in what you can do with it.  The “compost” was really only about 75% done due to the amount of pine needles, it was really a well cooked mulch – very similar to the “duff” layer in a forest.

Rather than bury you with text I will tell it in pictures.  Enjoy:

Cut away of the Finished Methane Midden. The layers of heat exchanger settled over 50%, with the bottom two resting on the ground. Not good - time for a redesign.

What a mess. And you missed all the swearing to get it to this point! Anyone need any yellow garden hose?

Then I started spreading the mulch.  The plan was to use the finished compost to start my willow/poplar coppice that I will plant in Spring 2011.  It is sized for about 80 trees and will have an understory of Russian Comfrey.  Will likely also put in some False Indigo and everbearing raspberries, but I get ahead of myself!

The coppice will be around 3 sides of our kids playground and will have a total row length of about 125' (22 m). This side is close to our fence and is only 2' wide -enough for 1 row of trees..

Good shot of how thick I laid the mulch down here - easily 4-5" (10-12 cm). This is the main width - about 4' (1.5 m) for a double row of willow. Thanks again to author Michael Perry for his help with this during his visit!

The final leg of the coppice to be. Yes, I have 2 wheel barrows... I also have 5 pitchforks - and each has a specific use! So much mulch, and I hadn't even used half the pile yet...

This post may get long, but I really want to pound home the shear amount of Good Work that can be done with one of these Middens – I was beyond giddy driving my barrows around the yard flinging compost at anything that grew! Plus it is a compost eyes view of much of my permaculture beds.  I have been asked if I used more energy than I created with the Midden.  Yes, I did.  But show me an oil rig that can do all this:

'Barrow load under my sole bamboo - a clumper. This will be its first winter -fingers crossed!


Mulch spread in my Asian Pear tree guild - I forked it around the perennials so as to not bury the groundcovers

Wheel barrow load of mulch for my sole apple tree. It speaks volumes that I spread most of this compost "by the wheelbarrow load" rather than the forkful. AWESOME! This still needs to be spread away from the trunk.

7-8 barrow loads went on my Sunchoke plantings. Sunchokes are not my favorite food, but this reliably cranks out 50#’s of food for no effort.

Here is the raspberry patch. It was rather overgrown so I hacked it to the ground and refreshed the soil with 8 barrow loads of Midden Mulch. Still not even 75% done with the pile!

Into the Guilds! Mulch under my heirloom Pear - a White Doyne which I have never seen in a catalog, but got from a nurseryman friend.

The other portion of the Pear Tree Guild. This shows one of my Paw Paw's, some hazelnuts, another pear, and a hardy kiwi on the fence. 3-4 more barrows here.

I had so much mulch I decided to start a new guild. This is a pine I bought the year we moved in and is just no starting to grow. In went an elderberry, some thyme, a service berry, and several dozen strawberries. And yes, I just had these lying around...

Mulching under one of my front yard "pretty" guilds, both Peach Tree guilds.

It was so incredibly liberating to be able to spread compost where ever I wanted to – flinging forkfuls into the rain gardens, into the prairie, on the lawn – without have to choose which plants to favor and which had to go without.  Also notice that my annual vegetable gardens didn’t get any mulch.  This was intentional – this mulch is very carbon intensive at this point, and will be heavily skewed to fungal decomposers which my perennials prefer.  The veg garden would have been fine, but the fruiting shrubs and trees would really benefit.  Plus I have another 5 yards of compost in my regular bin for the veggies.

The Methane Midden was lined with over 20 bales of straw. These were a wretched mess... perfect for a winter mulch for the veggie gardens!

Now the Methane Midden has passed, but OMG will it live on.  I covered everything in this post, plus 3 other guilds, 2 rain gardens, and even some into my mini prairies.  Imagine what your gardens will look like if you built 2-3 of these Middens a year?  I can’t wait to find out!

Energy is fantastic and very useful up here where it gets to -15 F (-26 C) in the winter, but being able to make this much compost, from invasive species and “weed” trees is where the true beauty is.

Over 8 yards of compost from one pile in the burbs?  Epic Shit indeed!

And I can’t wait to do it again – only BIGGER.

Be the Change!


13 Responses

  1. wow!

    viv in nz

  2. Hey Rob-
    I’ve been following your project all summer–congrats! This is truly amazing. I hope to leave the Middle East for my own homestead in two years time, and your Midden is definitely on my To-Do List!

    One question–you used pine, correct? Would that make the compost you harvest acidic–and if so, how does this affect the plants you are mulching with it?

    Keep up the good work! The world needs more people like you. . .

    • Jean, thank for your kind words.

      Yes, the Methane Midden’s feedstock was almost entirely pine tree limbs, and the needles resisting decomposition was the prime suspect for it dying after only 2 months and also why I have mulch instead of compost. It will definitely be more acidic than a deciduous based compost.

      That said, the only place it will likely have an impact will be where I put it down for the 2011 coppice grove 4-5″ thick (10-12 cm), and even then the soil under it is clay as is much of the soil here. In my experience it is almost impossible to alter the PH with mulches in a few years. It comes down to volumes and densities. A cu yard of compost weighs in at 540# (244 kg), and this mulch was much lighter. A cu yard of clay will weigh 4x that or more – and the clay goes down for 6′ (2 m) vs the 4″ of mulch. There just isn’t enough matter to change the Ph much. If you used only pine mulch several times a year, for decades, you could perhaps drop the Ph enough to affect the plants, but even then I am skeptical. The soils PH is mostly set by the subsoils and the environment and there isn’t much you can do about changing it significantly without moving obscene amounts of soils with heavy equipment, or with massive additions of rock dusts or sulfur; the Ph you have is about what you will always have. This is why those with high/low PH soils often resort to raised beds so they can completely control the soil composition – not practical for permaculture guilds. The vast majority of plants have a wide enough range of acceptable soil environments that they won’t even notice. An example from nature would be to see how many of the local forests in this area are mixed conifers and deciduous and still have a very similar understory as the pure deciduous stands.

      The plants WILL benefit from the huge influx of organic matter, soil microbes, water retention, and temperature regulation from the mulches.

  3. Double WOW! Ruth Stout would be so proud at how far you have taken this.

  4. This is awesome! Something I want to try when we move to our WI farm (hopefully next year).

  5. I imagine that the midden was too hot/ dense for many earthworms/ insects to move in. By letting it decay in an environment that favors microorganisms over small animals, you’ve created a buffet for worms, sowbugs, and all kinds of beneficial insects. Look for a population explosion in spring, and epic mushroom blooms in fall.

    I used a dump truck load of mulch on a similar sized property two and a half years ago. I’m in a warm climate (zone 7b), and I couldn’t find you a handful of that mulch anymore!

    • GS, the Midden sat static (70-85 degrees) for several months and was full of mycelium. Not as much macro soil fauna (sow bugs, centipedes, etc) as I am used to, probably due to the acidity of the needles, but this will be a lesser issue now that it is spread out. There must have been something though, as there were hundreds of spiders and they wouldn’t have been there without a food source. To spice things up, I mixed in a forkful of vermicompost in about every third barrow load to add in more good guys; leavening the bread as it were…

      The Decaying straw bales were riddled with composting worms, earthworms, and the usual suspects.

      It is amazing how fast the mulch disappears isn’t it? The best soils on my property seem to be under my wood chip paths, which is what convinced me to use wood chip paths in my veggie gardens as a nursery for soil fungi.

  6. […] 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 […]

  7. Salutations,
    In your blog you mentioned renting a 27hp Vermeer chipper and that you own a Bio-80 Shredder. In your opinion does either of these units shred the brush to the consistency recommended by Jean Pain? Are you aware of any DIY plans for building a Jean Pain type brush shredder? Or is there a dealer here in the U.S. for the French brush shredder company bearing the Jean Pain name? Or is the soaking of the brush chips in water the most important thing, more important than the brush chips size and texture?
    On another tangent, have you come across any information on somehow running a stirling cycle engine directly from the heat of a compost pile? Apparently there have been some demonstration models that can run from the heat from just the human hand This might be a way to produce mechanical power directly from the compost heat that could run the water pump . Please keep up the good work and keep us updated via your blog.

    With graditude,


    • Patrick – The Vermeer chipper makers a nicer chip than the Bio-80 which minces them. That could be solved with a larger screen though. The Vermeer will produce 3/4″ chips (2cm) that are about 1/8″ thick that were good – the smaller brush, which I should have been using anyhow, it often sucked through in longer strips. Nothing makes the type of shredding Jean described and I have not found an importer for the French shredders. The closest I have come to is taking large annual stalks – mature sunflowers or huge amaranth and running them through the Bio-80 with the screen removed. By holding the stalk to resist the machines desire to whip it thru without shredding I get a much more similar “chip” which is longer. Unfortunately, stalks like this, when greenish are far to rich in nitrogen – piles of pure stalks exceeded 185 F (85 C) which is was killing the beneficial microbes and fungi. Water is very important, and the overall size of the pile will be very important too. Chip size has a role to play, while these chips do facilitate bridging and air flow – none of my piles have gone anaerobic – but Jean spent many years perfecting his shredder and he seemed to rarely work without purpose. Perhaps the longer shredding’s facilitate bacteria spreading, water wicking, or something else.

      A Stirling engine has been brought up by some local engineers, so that may be something to try as well.

      Unfortunately, I will be forced to sell my dump truck this winter, so the current pile will likely be my last for some time as I will be without the equipment to move large quantities of chips efficiently.

  8. Thanks for taking the time to respond…I downloaded “The Jean Pain Method” Ebook, so far only looked at the pictures ,but it is on my winter reading list….my brother Duane came up with the idea of running the brush through a hammer mill, like is used to grind livestock feed, but I think that would produce something more akin to sawdust. Would the smaller particle produced be an advantage ?I also noticed in your first midden you first put down cardboard before building the pile. What is the advantage of that? How is this winter’s pile doing?

    • Smaller particle size would be a DIS-advantage as it will hinder air flow. larger size is critical to allow the chips to bridge and allow for airflow within the pile to keep it aerobic.

      the carboard was to block persistent quack/couch grass in that section of my yard from growing into the cooler edges of the pile.

      The winter pile is “dead”. I was pumping water through it and getting about 1-2 gallons per minute at 100 degrees F with a pile temp of 120 F, which was decent considering the nitrogen content of the pile was lower than I wanted. But then we got a sharp cold snap while I also got sick with a stomach virus and then we had Thanksgiving. The long and short is that for a week with air temps at under 20 F (-6.5 C) I was circulating water through an uninsulated 55 gallon drum which resulted in heat being vented to the atmosphere faster than the pile could replenish it. Pile temp dropped to 55 F, which is below the mesophillic temp range and the pile essentially went “passive” . I will have great mulch in the Spring, but the pile for use as an energy source is nil so I disconnected the pump to avoid it freezing.

      Again, particle size 2cm x 2cm x .5 cm at least, soaking the material, 30:1 carbon:nitrogen, and volume of material (mine was 3 meters x 3m x 2.5 m and likely too small for our cold winters) are the critical factors. Larger is better and ensuring you are not taking heat out faster than the recharge rate of the bacteria- which is rather low. I was getting about 1000-1500 btu/hr from my 110 m of heat exchanger in the winter pile. But once external air temp dropped, the pile needed more of its heat energy to maintain homeostasis.

      In short I feel that the piles are best for maintaining temps as a slightly positive heat sink -ideal for maintaining temps in methane digesters, tilapia tanks, vermiculture beds, etc where heat needs are low (75-100 F) and the compost can replenish heat lost to ambient air. For larger heat exchangers, a much larger pile is needed as is shown by Jean’s MASSIVE 80 ton piles. In my case, I see alternating 1-2 meters of compost beds surrounding 300 gallon tiliapia tanks in cool greenhouses as a great way to reduce energy costs for both the green houses and the Tilapia tanks. External energy is still needed, but to a lesser extent and compost is supplied year round.


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