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!