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.

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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.

Learnings:

  • 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!

-Rob

Coppice Compost Harvesting

More to come soon as I do a proper write up, but here are some links I thew on Faccebook from today’s Coppice Harvest which netted just shy of 15 cubic yards – about 6000#’s.  Holy crap was this a fun day.  Broke the hitch mount off the dump truck and I barely even care.  The Vermeer 600XL chipper is bad ass.  Its also more tool than this project needs, but figuring that out was one of the reasons I rented it.  Thanks again to Chris and Mark from work for helping me out!

Mini-Videos

Photos

And thanks to coppicing, no trees were killed in the making of these videos!

-Rob

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!

-Rob

Suburban Pollarding: Making your own mulch

There are several themes here on One Straw, but it can all be summed up with the statement that we need to build a regenerative culture as we skip merrily down Energy Descent.  To do that we need to rebuild our culture, grow more of our own foods, find a way to power our civilization, learn a shit ton of new/old skills and stabilize the climate whilst dealing with the next 50+ years of weather silliness and rather a lot more.  Any good permaculturist likes to hit more than one goal with each throw so I have been focusing on biomass lately.

I really need to write a biomass specific essay, but here is the skinny.  Where I live in south central Wisconsin there is only fair solar and wind resources, no geo thermal to speak of and it has been several million years since we had a decent tide.  But, thanks to plentiful rains, if you stop mowing your lawn for a decade you get a nice old field sucession.  They don’t call it the “Northwoods” for nothing; we are really good at growing trees.   Solar is a great way to make electricity and you would be insane to not consider something with such crazy low maintenance needs, but biomass has alot of fringe benefits to offset the labor input.  Primarily – if you do it right you sequester literally tons of carbon.  We all know that is cool ever since Al Gore told us so, but not only can we help offset truly catastrophic climate change, if we do it right, we can also heal our soils to feed our burgeoning billions.  Carbon is a pain in the atmosphere (above 275ppm anyhow), but DAMN is it cool in the soil.  We need to put it back.

Here is one of my all time favorite sustainability facts:

By raising the organic matter content by 1% in the top 6 inches of soil, you have effectively sequestered all the atmospheric carbon above that area of soil.

Dang, sucka! This is why agriculture is such a huge contributor to global climate change – conventional ag destroys organic matter, removing it from the soil and getting it airborne through massive nitrogen fertilizers and tilling. But the simply beautiful thing is that we NEED to raise the organic matter content of our soil by 2-5% everywhere if we want to produce food organically and by doing so we heal the atmosphere.  Trees, woody stalks, and straw are the best ways to get carbon out of the atmosphere (plants do it for free and are, by nature, carbon negative).  The trick is to harvest that biomass efficiently and then process it in such a way as to sequester it for the mid/long term.  Enter my Tuesday project.

I live right on a freeway.  In addition to the noise and pollution, the salt spray in the winters also have a tendency to kill off or stunt just about anything I have planted there (trying siberian pea shrubs).  But buckthorn thrives.  Now I would never intentionally plant buckthorn, but there are several specimens on the D.O.T. side of the fence and one mature one just on my side.  I have left it up as a windbreak to protect a maple I have planted.  But that buckthorn is rather vigorous, as is their wont, and needs to be hacked back every few years.  We call it trimming when its a chore and the material is thrown away, but when it is done with the specific goal of harvesting the biomass the proper name is Pollarding.

Here is a shot of the buckthorn with about 20% of the south side of it pollarded.

Its a BIG buckthorn! Pulled about 80#'s of biomass out and you can barely tell.

I essentially limbed up everything I could reach that had limbs facing in the 30 degree arc around the maple.  This freed up a lot of room, and made too big piles of material.  I separated these by use – the larger diameter wood (.75″-3″) I intended to chip up for oyster mushroom growing media, the leafy material at the end of the limbs would be shredded for compost.

the left pile is half off frame and is intended for compost, the right is about 10' long and intended for mushroom media.

I did not put any of this down as mulch due to the presence of very green berries on the tree.  By composting this material I will essentially sequester half the carbon from the tree (the rest is off gassed by bacteria) for 5-50+ years in the soil as humus which is pretty stable.  The results of chipping are always mind boggling.  What started as enough material to fill my dump truck bed (11 cu yards) I am left with about 2-3 cu feet of wood chips and perhaps 9 cu ft of green shredded branches that will compost down significantly.  Total weight was roughly 100#’s.

Chips in foreground for mushroom growing, green shredded material in background for compost.  Entropy!

After composting it will be about 15# once the water is consumed by the bacteria and half the material is off gassed.   The chipper does use fuel, but this stunt only consumed about 1/2 a cup which is less than my neighbor used mowing his lawn while I did this.  Larger chippers are more efficient and can be run on methane from the midden or ethanol if gasoline engined, or biodiesel if not.

The shear scope of our problem can be staggering at times.  I would like to add 1″ of topsoil to my new garden, which is 1100 sq ft.  That works out to just shy of 7000#’s of compost.   For one garden.  That is why I am becoming more and more convinced that the single most important thing we can do is to plant trees.  LOTS of trees.  The great thing is that it isn’t that hard.  1.5 acres of willow will produce 22000#’s of chips annually (harvesting .5 acres a yr) for 2 decades or more before needing to be replanted.  And that is dry trunk chips only, not the leafy biomass of the fronds.   While we can’t grow the biomass needed to heal our soils in our own backyards, we can certainly plant enough trees and “woody” plants into our home landscapes to maintain the soils once we have healed them.  100 acres of marginal corn land – say near rivers that flood seasonally and shouldn’t be planted to annuals anyhow- planted to willow coppice would produce enough biomass to rebuild almost 100,000 sq ft of garden a year.  Every year after year 3.  In 8 years we could have a garden as large as mine in every yard in my hometown of 500 homes churning along at 5%+ organic matter  and be producing 500,000#’s of food annually while also sequestering hundreds of tons of carbon annually.

When combined with energy systems like the Methane Midden, which has 6000#’s of chips in it, sequestering carbon can also offset carbon emissions for energy production.  I planted 15 willows on our property this year specifically to begin coppicing in a few years.  Next year I will pull rods from them to start 50 or so more.  Box elders are another strong coppice candidate in this area.   The hedgerows for a 5 acre sustainable produce farm divided into 1 acre plots would grow enough biomass to run a gasifier for a year while sequestering 11000#’s of carbon to be added back to the fields as biochar to help create terra preta.

We can partner with nature to heal the damage we have done.  Even in the burbs.

Be the change!

-Rob

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.

Testing

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.

-Rob


Jean Pain Compost – Mulch Soak

Its been about a week since I picked up the 8 cu yards of mulch from the municipal yard with BART.  The grabbing of the mulch was almost instinctual, but over the past week some planning has set in as I need to be more methodical if I am to run a true Proof of Concept, let alone produce several dozen cubic meters of highly combustible methane gas within 20 feet of my home.  But first, lets catch up on the past week.

 

140 degrees in less than a week - total prep? Pushing the "up" button on the dump truck...

 

A few on lookers had expressed concern about the ability of pure pine tree waste to decompose.  That made me pause for a day or two- would the acidity funk with the microbial mix?  What about the resins?  No worries though, the pile steadily warmed and within 5 days was roaring away with steam drifting off each morning.  Took a temp reading today and it was well over 140 in many spots, and the entire center was over 135.  Hmmm… 4000#’s of material at 135 degrees.  Yep, that should be more than enough bTU’s for the project!

There are several really unique things that Jean Pain did in his methods, most of which I will try to capture.  First – he used brush.  At first glance, wood chips seem to be way to high in carbon.  But I have seen mulch piles heat up on numerous occasions, but they don’t stay hot long once they burn through their nitrogen.  Jean’s stayed over 100 degrees for 18 months!  A careful watching of the You Tube vids and readings of his book show a key point – he used GREEN, leafy brush.  Green brush has a ton of nitrogen and sugar rich sap, and the pile of pine I snagged was predominately green in color – i.e. lots of nitrogen.

Second, Jean soaked his piles for 2 days in a giant ditch.  Here is the what I am convinced this does and why it is so vital in his technique: the wood chips literally saturate themselves with water over the course of the 2 days.  This provides a store of water for the pile to keep the bacteria from getting thirsty for literally months on end, but does not force the pile anaerobic due to the large particle size of the chips; the bridging allows for enough air to circulate.  The bacteria live on the edge of the chips, and as they consume the water, more is leached from the interior of the chips through capillary action.   From what I can tell, when Mother Earth News did their expirements on his methods in 1980, they skipped this step.  I believe that to have been a fatal flaw, and one I do not wish to make. But how the hell do you soak 200 cu feet of mulch? With giant plastic totes of course!

 

I bought these last year off of Craigslist. Why? They were $25 each and just HAD to be good for something!

 

These totes are HUGE – about 54″ cubed- and they hold over 2 cu yards  or 350 gallons.  I bought 7 last year on a whim, and gave 2 to a friend in exchange for the use of his pole barn to store them in and a clearwater 300gph pump from harbor freight for my Appleseed BD Processor.  I love my life.  Anyhow, I figured  that 3 of these would be about perfect to fill with chips and water and let them sit for a few days to soak up all the goodness while I do some other projects like planting the 500 sweet potato slips that showed up last week.  It took about 3 hours for my “intern” Kevin and I to get them from storage, drag them to the backyard, and fill them up.  I also filled 3 of the 55 gallon drums I also bought last year for the biodeisel project.  2 of them will be the batch digesters, but I am getting ahead of my self.

 

2 of the 3 totes filled, along with 2 drums in the foreground. I have planted a bit more than my neighbors...

 

Luckily before we began to fill them I had an epiphany as to how to drain them.  Tipping on of these bad boys will NOT be an option once they are full of water, and even drained I think we will need some fancy levers and my 3 ton jack.   My solution?  I put the garden hose all the way to the bottom of the tote and filled them up as we schlepped mulch in.  Once the water reached the rim, I unscrewed the hose from the house and hung the female end over a bend in the gutter about 7′ up.  This preserves the water in the hose and will allow me to siphon out the water on Friday.  If it works, it will be brilliant!

Next steps will be leveling the 100 odd sq ft needed for the Jean Pain mini digester compost pile.  My plans there are to wall in the entire pile with 2-3 tiers of straw bales with the two drums in the center of a 9 x 12 rectangle.  The straw will provide a (relatively) unobtrusive structure for the neighbors and, once staked, enough support to contain the pile.  Also, I am hoping that the extra insulation will be an added benefit.  Still sourcing hose to wrap the drums with to regulate their temperature, and I have another friend looking into pumps.  After than I will need to rig up the drum lids with some barb fittings and hoses to pull off the methane gas.  And then finally, the big unknown is the methane storage.  Several options in the hopper- Jean used tire inner tubes, but not sure how OSHA would view that.  Kids play in my backyard…  Safety is a BIG concern.

Should have a post up later this week showing the completed pile, and will likely fill the drums either Friday or next week. Also, this thing needs a better name than the “Jean Pain Compost Methane Batch Digester Proof of Concept”.

I’ve always liked alliteration…

Enter the “Methane Midden

-Rob

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