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!


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!


Introducing Midden Part Deux: “L’eau Chaude”

Right.  So the past 2 weeks I was out of country – 6 nights in Victoria, Australia in the Great Otway National Park and then 7 nights in New Zealand 3 nights in Kiakoura on the South Ocean and another 4 getting to know Wellington.  It blew my mind and I am in no condition to post about it yet – still fermenting.  But time waits for no man, and with the leaves falling it is almost past time for me to get my arse in gear and build the second midden.  So here goes.


Introducing my Husky 235. 1.8 hp and I dropped and limped 3000#'s of biomass on a .25 cups of fuel. Efficient? Can I get a Hell Yeah? Wear your safety chaps, the femoral artery waits for no man.


First off, this midden will have several differences.  The first, of course, is in intended use.  This Midden will be designed to produce hot water (l’eau chaude) v. the Methane Midden’s failed attempt to make methane (botched the PH and ran out of time).  Second, this the Midden L‘eau Chaude will be constructed with freshly harvested brush.  That means a few things.  Like I needed to find 8000#’s of brush and that is a bit more than my backyard can supply.   Oh, and I need some new tools like chainsaws.  And finally I need a Big Az chipper.  How does a trailer mounted 27hp Vermeer sound?  It sounds kick ass to me as long as no one goes Fargo…  Renting the chipper for now, but if this works, I can see a huge shredder in my future.  Someone has to figure out how to run these on ethanol and methane, right?  Perhaps…  that shredder runs $8k.

We’ll get into the technical pieces of the  l’eau chaude in future posts, but for now, lets talk through sourcing the brush.  I called some of my friends that own land and was able to secure enough material in no time.  It isn’t hard to wonder why.  Say you own 20 acres, 10 is in woods.  You get a call from a friend who is offering to cull invasives from your woodlot.  For Free.  Oh, and he’s going to use the material to do some Epic Shit.  Done deal.  I have 3 lots that I am working on this week.  The plan had been to drop a bunch of Box Elder since it grows 6-10′ a year here and can be invasive, but that has run into some hitches.  First, they are dropping their leaves, and I need the leaf nitrogen in the Midden.  Second, the main wood lot was cleared of Box Elder a decade ago.  Huh.  So the land owner and I walked his lot and it became very obvious that there was plenty of species still in leaf, and the sources were, if anything, even better: buckthorn and honeysuckle which are wicked invasive in this area.

As we were felling these, I became worried that there wasn’t enough green material in the mix – the honeysuckle especially was only leaved on the ends of the trunks due to the dense canopy, and most of the buckthorn we were dropping was crazy mature – we had some with 7″ trunk diameters!   Looking around some more we noticed that mulberry was still in full leaf and they are a very aggresive tree in their own right.  Out came my new Husqvarna and we dropped several 7″ trees that were leaning over his paths and would become issues in the next decade.  These were limbed up, with the trunk being lopped up for firewood.  tomorrow, at the property where I market garden we will be dropping a HUGE mulberry that is shading a vegetable patch with the same technique: limbs into the Midden, and the trunk wood will be used for space heating.

The honeysuckle, small buckthorn and mulberry look exactly like the shrubby brush that was coming out in the Jean Pain videos.  Still TONS of trial and error to be done here, but it looks like 1″ or less trunk diameter is the money width for composting.  The 3 bins I have going at home were built using 1.5-2″ willow and are far too carbon rich; I needed to add nitrogen at the first turning.  1″ trunks would be a 2 year rotation in a willow coppice.  I have no idea what pushing a coppice that hard will do, but it is likely it will burn it out in 5-10 cuttings.  That said, I was cutting mulberry out of the landowners asparagus “patch” (its .5 acres) that was 6-7′ tall and has been mowed every fall for 15 years.  Those stalk were ideal.  Hmmm, with stalks that small harvesting gets easier.  How about a mulberry/willow/poplar coppice on 12″ spacing and a 25hp straight veg sipping Kubota (sunflower stalks compost FANTASTIC) pulling a two row Gehl sillage chopper…  Those things are dirt cheap on Craigslist as no one uses such small equipment any more.  Huh.

But for now I am focusing on harvesting from the woods.  With about 6 hours of labor in, we have 8-9 piles of brush larger than the dump truck, and Friday I am putting in a full day now that my sawing muscles are hardening and felling a significant amount more.  Tuesday will be the final day of prep, and the rental chipper gets picked up on Wednesday at 7am.  Goal is still for 2 loads, 8000#’s, of green material.  These will go into the plastic tubs for soaking, and then construction begins on Tuesday 10/19!  Pics will be up tomorrow night on the brush hogging.

Can we turn the invasive species of today into the carbon sequestering, energy and food producing fuel stocks of the next century?     Stay tuned.

Be the Change!


Midden Mini – Update

Finding it extraodinarily hard to find to time to write with everything thats going on (tours, workshops, Real Job, kids home, potato harvest, epic vacation planning)  but The Good Work is not suffering.  This post will be text only as I don;t have time to upload and edit the pics.

The main updates on the ‘Midden are that the pile is cooling – down to 110.  That is due as much to its age as to me tearing into it every week to tinker with the, now, primed digesters.   So lets talk about those digesters.  2 weeks ago I filled one of the 55 gallon drums with ground up box elders, and the other with ground up lambsquarter.  Why?  Both plants are prevalent and rather despised weeds hereabouts.   To those not sharing the local stereotypes on plants, that means that the biomass from those two plants can be had for free and in large amounts, or in the case of box elder, one can be paid to remove it from woodlots.  Nice.

The side by sides were to see if a more carbon rich (box elder) feedstock would screw things up.  Goal in biogas production is to shoot for normal composting C:N ratios of 25-30:1.  The box elder was likely closer to 40-50:1, the lambsquarter more like 20:1.  Jean Pain never measured, and I like flexible systems.  We *know* 25:1 will work, so lets push the envelope to see what happens.  Unfortunately, 2 of my 3 steel drum lids had the bungs rusted on (snapped a bung wrench trying to open it) so I can only seal one.  I choose the Box Elder.  Weeks went by with nothing.  Temps are good – 90-100 with digester feedstock at 95.  I should be cooking right along, but wasn’t, or if I was I wasn’t capturing it.  That meant I needed to reseal the barrel as the old gasket was, well, old or that the chemistry had gone wonky.  I sealed the barrel up with silicone and then I took a sample to a friend with lots of lab equipment including pH testers that give near instantaneous readings to within .01.  Results – the Box Elder batch was sour.  REAL sour : 4.8 !  Methane microbes like to be 6.8-7.4.  Oops.   Making methane is a delicate dance between acid producing bacteria and methane producing ones.  I don;t know enough about the bio-0chemistry, but my hunch is that the prevalence of carbon in this digester tilted the balance, but there are so many variables.

So I stopped by my friend who runs our local sewer utility and picked up 8 gallons of biosolids – the left over treated turds of our village.  Our municipality sterilizes the processed effluent with lime as not many bacteria live past a pH of 12.  So the left over solids are about 10.4 pH and are still high in organic matter.  3 gallons of slurry and had me up to 6.1 pH, so I threw in another 2 gallons and will test again tomorrow.  I also threw in another cu ft or so of compost to reinoculate it.  Why?  Because I have come to the same conclusion as Will Allen at Growing Power – that compost fixes nearly everything microbial- if you throw 500 billion bacteria, spread across 15000 different species it is rather likely the one you want is in there and will thrive if you set the environment up.  Fingers crossed.

Back to our story.  When I went into the lab today, I also tested the lambsquarter digester for pH.  This unit had a different odor to it, less sickly sour and more of a deeper, more robust putrescence.    It was also bubbling under the slime.  Huh.  Could that be methane?  The pH test of that looked much better – 7.10!  Right in the sweet spot. So I switched over the methane capturing lid and now the lambsquarter digester (#2) is sealed and plumbed to collect gas.  Perhaps I will have video up soon of itty bitty bubbles coming out the discharge tube.  If so, I will capture some and take them back to be tested at the sewer utility as they have equipment to test for methance gas quality.  And since I am using their Biosolids-  I now qualify as a test project so I get to use all their toys.  Awwww yeah.

Also staking out felling rights to several local woodlots and will likely be buying a chain saw or a wicked good axe to take down several hundred 3-5 yr old Box Elders for the next phase of the ‘Midden as we switch gear for hot water production, perhaps in September.  Problem is I will be out of town for half the month and I lost my “intern” to school so not sure if I want to start it before or after.  We’ll make it work.

MUCH more to come!


Food + Fuel + Fertility = The New Paradigm

Food. Fuel. Fertility.   Of late, those 3 words hammer through my brain like a sledge whenever I get going on a new project.  The reason is simple – I am convinced that our agriculture has to do all three if we are to build a new culture to survive the new reality of Climate Change on top of Energy Descent and our burgeoning billions.  We talk and talk of sustainable culture – but I don’t want to sustain what we have now – the fear, the pollution, the waste – I want something far better.  We need a Regenerative Culture. The Age of Exploitation must come to an end – the Age of Healing has arrived.

The Methane Midden is a good example of this thinking.  While significantly on the energy/fertility side with its 4-6 months of hot water or methane on top of the 4000#’s of compost, it is also planted with squash and tomatoes to produce hundreds of pounds of food.  The system is still being tested (the plants aren’t loving it) but the potential is immense.  7 weeks in and the pile is still over 125 degrees – with no turning or maintenance at all.  Dang!  Tomorrow I am going to harvest several hundred mature lambsquarter that are 9′ tall to be shredded for the methane feedstock.  Much more to come on that project!

With that task of harvesting tall stalky plants in the back of my mind, this morning over breakfast I went on a fantastic internet fueled thought tangent on the feasibility of a fuel tweaked Three Sisters guild.  It is so simple, which is why I am so excited.  First – take the standard Three Sisters of corn + pole beans + winter squash and swap oilseed sunflowers for the corn.  Why?  Because my car and 2 wheel tractor run on diesel.  Journey to Forever says that you can get 102 gallons of oil from an acre of sunflowers – 43,000 plants on 1′ spacing.  But we are wanting a polyculture so we will need to let some light in by spreading the sunflower canopy a bit – say cut the spacing in half to 25,000 plants or so.  That still leaves enough plants for 50 gallons of oil if we use oilseed varieties.  Then take the understory and add back in the squash.  Monoculture will get you 10-20 tons of squash per acre.  So again, lets cut that down a bit and say 18,000#’s.  That is ALOT of food.  Food that keeps all winter long. Finally, we are vegetarians so we needs our protein.  Add in the soup beans.  25 bushels per acre is typical @ 60#’s a bushel.  Again, cut in half for polyculture and you get 12 bushels of beans, or 720 pounds.  So to recap our acre is now growing enough seed to produce 50 gallons of oil, 18000#’s of squash and 700#’s of dry beans –both of which keep for months and months.  That is rather good.   Lets make it better!

Remember the thought stream that got me to this point over my now cold steel cut oats.  Chopping down cellulose rich tall plants for methane fuel stock and compost.  25,000 8′ tall sunflowers…. lay them down end to end and its over 37 miles.  I haven’t weighed one, but figure they weigh 5#’s each.  That is 62 tons of green material that is going to be pretty close to perfect C:N ratio by harvest time.  125,000#’s of material – composted down with a 75% loss gets you to about 30,000#’s of compost, or 55 yards.  That seems high so I would love to prove the math.  That is enough to spread the entire acre with .4″ of compost- a very healthy amount and far more than I apply annually in my market gardens.  Fertility would increase to say the least.  62 tons of material would also be enough to build 8 Methane Middens so that we can heat our winter greenhouses or the chicken barn.  Dang sucka.

Back to the fuel part again.  50 gallons doesn’t sound like much.  And it isn’t.  Most of us only get 22 mpg and  drive 12000 miles per car per year – 540 gallons per year per car.  Ouch.  But we all know that we will drive ALOT less in the future and most cars are fuel hogs.  My VW TDI gets 42 MPG towing a 1000# of cargo in my trailer.  Have I mentioned I love my car?  So, even saving 5 gallons for the Grillo to till the acre, we still have enough oil to drive over 1750 miles towing all those squash and bushels of beans to market.    If we relocalize that is 175 round trips to town 5 miles away – 3 trips a week. Huh.

But I want to re-stress my loathing of the food v. fuel argument.  It is a farce if you think it through and know the science of biofuels-even ADM fed their ethanol mash to tilapia.  So we take the 25,000 sunflowers, grind up the seeds (will need some energy there – unless we build a bicycle machine to do it), and press them.  That seed mash left over from the pressing doesn’t just disappear.  In fact, about 50% of the total oil is essentially impossible to remove from the pressed seeds without solvents, and the protein and carbohydrates are still there too –i.e. the food value of the seeds is still there.  That means you still have 1500#’s of protein rich (40%) meal to feed to your livestock.

Can we rebuild the next 20 years to allow us to transition to a less energy dense future?

1 acre nets 18,000#’s of squash, 750#’s of dry beans (4500 cups cooked!), 1500#s of animal feed, 30,000#’s of compost after you have heated your buildings with 8 Methane Middens worth of energy, and you also managed to make enough oil to power the tractor and drive to town 3 times a week for the next year.

On one acre.

Be the Change!


Fund the Methane Midden!

I have taken the plunge and set up a Project on to help fund the next phase of the Methane Midden.  Kickstarter is a funding site designed to use blogs and social media to help fund small, creative ideas.  The project owner sets a funding goal ($500 for me) and a time limit (July 31st, midnight!) and lets the world know about it (this post).

Then the world pledges small amounts $1+ and spreads the project via their networks.  Before you know it the project funding goals have been met!  Sounds great right?

A few caveats – no one is charged (they use Amazon) until the TOTAL pledge goal is reached – we need to get at least $500. AND no one is charged until the project period is over (Aug 1st 12:01am).

And the most important point – there is no upper limit to the pledges.  Anyone who has read this blog at all knows I can find creative ways to spend money to save the world…  I have also added a widget to the right sidebar.

So I am asking you to help this idea out; help me raise the money needed to get it to the next level and make this awesome idea happen!

Methane Midden: 2 Week Update

When we left the Methane Midden 2 weeks ago it was 75% finished and consisted of 2 55 gallon steel drums destined to be batch methane digesters wrapped in 290′ of garden hose for temperature management.  Around these digesters we then placed 4000#’s of freshly chipped green brush that had been soaked for 2 days in some giant totes and into this soaking wet brush we layered another 240′ of hose which is intended to absorb heat from the pile and complete it as a mini version of Jean Pain’s epic methane and hot water producing brush compost piles.  Much has happened in the past 2 weeks, so lets catch up!

First off, we needed to finish the pile with another 18″ of material.  Alas, we were out of brush, so we needed to be a bit creative to find another 2000#’s of material in a jiffy. So Kevin and I hooked up the trailer to the Golf and headed back to the municipal yard to see what we could find.  While not ideal, we were able to scrounge up about 1200#s of grass clippings (likely sprayed with Chemlawn) and then went back for a load of about 800#’s of wood chips.  The thought was to shred the wood chips in my Bio-80 shredder to reduce particle size and then to mix this with the grass clippings.  The result was a very good looking mix that had decent moisture content, plenty of nitrogen and available carbon.  My primary concern is that the grass clippings will mat depsite our attempts to mix them well with the shredded chips; time will tell.  Here is the pile of about 6000#’s of material (and another 2 tons of soaked up water):

5 tons of material: 3 tons green brush, 1 ton grass/chips. 1 ton water.

The added material gave us about 6″ of mulch on top of the drums and raised total pile height to a bit over 40″ which is my preferred pile height.  Next up was a top layer of straw to prevent excessive moisture evaporation and to insulate the pile somewhat to keep temps up.  We want the BTU’s in the water not the air after all.  Took about 2 bales:

All tucked in! about 3-4" covering the entire pile. In winter I would add another 6-8". Makes it look nice for the neighbors to boot.


Steel Drum Heating/Cooling

This was all finished within a week of the last post.  Pile temps at this point were stuck at 123, but within days of adding the top we shot up to 132-136 in many spots so we began to start testing.  First, I filled one drum with water to test how long it took to get it to 100 degrees (city water is 52 degrees).  Within 4 days the drum was up to 100 degrees, gaining about 8 degrees every 24 hours.  Of course, this slowed as the temperature variation decreased between the pile and the water, but was still 118 within 8 days total, about the time the pile was a steady 135.  Max measured temp in the drum was 124 after 12 days, though there were cooling runs in there.   System proof #1 was locked in: we could heat water to over 100 degrees, though this was never in much doubt.  Next up we needed to see if we could cool the water in the drum.  Using 52 degree municipal water with the tap set at about 8 gallons per minute (gpm) (fill a 5 gallon bucket and time it with a stop watch and then do the math) I was able to drop the drum from 118 to 112 in an hour.  This was very encouraging and I am confident that I can get the drums to under 100 in less than a day.

Water Heating

While this was going on, I was also taking temps of the water as it exits the pile.  This was far less encouraging.  Initially, the first 10 gallons of water were wicked hot – essentially pile ambient of 124 or so.  However, very soon after temps dropped quickly and by the time 20-30 gallons had gone through the pile water temps at pile exit were down to 64.  Oi!  However with only a few minutes of thinking this through several glaring design flaws were identified — a direct result of my planning this on the fly.  First off – 530′ of hose sounds like ALOT of hose.  And it is, but given the small internal dimensions, even at 530′ total water in the hose is under 30 gallons, and probably closer to 24.  That means at the 8gpm, fresh water only had 3 minutes in the pile.  That is not nearly enough time to pull in much heat as was proven by the small temp gain.  Also, using rubber coated garden hose was an expedient, but not well thought out, tubing choice.  The rubber is almost certainly acting as an insulator, reducing the piles ability to conduct heat into the water.  Finally, starting with 52 degree water means I have a long way to go to get to my goal of 120.

Initial Conclusions

  • Midden will heat 110 gallons of water to well over the 100 degrees needed for methane production
  • Water cooling is sufficent to regulate drum temps to within 95-100 degrees despite being in a 130 degree pile
  • Current configuration will not heat water sufficiently for domestic water use.

Due to some upcoming events – a tour of our home gardens by the Madison Permaculture Guild and my workshop at the MREA I am postponing charging the methane digesters with material until 6/22 at the earliest.  That said, there is still enough time for some tinkering, so I decided to play with the hot water side as those results were really disappointing.

Modification #1: Closed Loop Water Heating

So, while the results of the outlet temps are discouraging, there are some nuggets in there to be excited about upon reflection.  First off – I am getting 10 degree rise in a matter of minutes at a relatively high flow rate.  There is an immense amount of heat energy in the pile – sitting near it on a still day you can feel it radiate off– I juts need to find a better way to capture it.  An obvious choice is to close the water system by pumping it right back into the pile.  To accomplish this I need to get one of the pumps I bought for the Appleseed Biodiesel processor from Patrick’s house.  A quick call explaining what I am up to was more than enough to have Patrick excited enough to come over.

Meet Patrick, he builds underwater robots. Yeah, thats right.

Patrick forgets more about electronics over breakfast than most of us ever knew.  His day job is building and piloting underwater remote operated vehicles – like the ones that found the Titanic and are trying desperately to staunch the leak in the gulf.  Patrick has also been to Antarctica a few times to help them fix their equipment.  On top of all that, he is wicked smart and wants to save the world.  He also has a pole barn that he lets me store alot of my stuff in.  Good guy to have around.  I called Patrick to see if I could get one of my pumps, and he came over the next day, not only with my pump, but with it mounted to a base and with a slick motor controller so we would play with flow rates.  Did I mention I like Patrick?

The pump is our “do anything” pump that we use from everything from ethanol to biodiesel to syngas cooling to this.  $40 from Harbor Freight, close to indestructible, and will pump up to 650 gph with its .5 hp motor.  We have 5 or 6 laying around or in use at any time.  However, 650 gph (10.8 gpm) is too fast hence the motor controller – which is essentially a dimmer switch for electric motors.

Motor controller set at about 66% or 7gpm. Plug the controller into the outlet, and the motor into the controller. Slick.

With the controller on and the system on closed loop pumping into the pile, then into a half filled 55 gallon drum, and then back into the pile we were able to run it continuously to see how high we could ge the temps.  66% gets us about 7 gpm and we ran it on closed loop overnight and got a steady 94 degrees come morning.   That is a huge improvement over 62 degrees, and enough for space heating, but I still want 120.  So then we let the pile warm up for a day, and ran another test at 30% or about 4 GPM.  This is really too slow for the pump and will burn it out over time, so we only did it for about a much shorter time.  Intake water was 80 degrees at the start.  After 45 minutes here was the result:

Actually we had 104 for 30 minutes and then the sensor shifted and we lost 3 degrees for some reason.

Now were talking!  That is very encouraging given that even at 4 gpm we only have about 7 minutes in the pile.

Next Steps

As I said, in 2 weeks we will run the methane experiment.  Once we prove / disprove the ability to make burnable gas in the system I will disassemble the methane portion to reduce the chance of serious accident.  At that point we will really focus in on getting that temp up to 120.  How?

With 2 55 gallon drums in the pile I already know that there is enough energy to bring them up to over 120 degrees – what is unknown is the recharge rate without draining the pile’s heat.  I also strongly suspect that with only 25 gallons of water in the pile in the current system there is not enough time to bring the water up past 104 degrees.  Answer?  Plumb the drums into the water heating system – water flows into drum #1 from the pump, then works it way into drum #2 and then through the 530′ of hose.  In one swoop we increase the waters time in pile from 7 minutes (at 4 gpm) to about 35 minutes by jumping from a system volume of 25 gallons to 135.  That should make a HUGE difference.

Second we need a better pump.  The clearwater 650gph is a GREAT pump, but simply too strong for this.  Luckily there are incredibly awesome pumps available for radiant floor applications made by Grundfos.  How awesome?  How about going from .5hp to .04hp and still maintaining 2-17gpm?  What about having 3 spd settings from the factory?  What about only having a AMP rating of .75 – yes this pump will only use 90 watts!  Thats like a quarter a day to run nonstop.  Plus, if anything, it is even better made.  $100 at Menard’s.

Third, we may very well need to swap out the garden hose.  If options 1 and 2 don’t get us to 120 we will need to get serious and buy PEX tubing.  Again, looking to the radiant floor applications here.  PEX is designed to be heat conductive, is flexible, takes heat ranges from 35-230 degrees, and is as inert as any plastic (insert cynicism here).   It is more expensive, but has alot of upside and comes in 500′ rolls.  Also, swapping tubing would mean a complete tear down of the pile, something I am loathe to do.  Again, hopefully a new pump and plumbing in the drums solves the issues.

All in all the first 2 weeks with The Methane Midden have been awesome.  This is the most exciting project I have been on since we first started on the gasifier.  Space heat+hot water+compost with almost no moving parts other than an nearly indestrucible pump.  Most importantly, the only skills needed are how to run a pitchfork and screw in a garden hose. Total price, even with pump, will be under $300 including stakes, drums, hose and straw.   If I can get the water to 120, or even close, consistently then I plan on building a new pile in the garage this winter, doubling the insulation, and plumbing in a heat exchanger (old car radiator) to be put in the hallway of our first floor.  Yep – space heating a house in an HOA with compost on under a quarter a day in electricity while sequestering carbon from garbage.

Want to help fund the Methane Midden?  Pledge to my Kickstarter project!

Be the Change.


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