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Getting wood chip compost to heat up  RSS feed

 
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I'm attempting to get heat from wood chip compost.  I did a modest amount of homework first but my pile isn't really cooking.  Please let me know if I'm doing anything clearly wrong.

First off, I should have temperature and moisture sensors buried in the pile for data analysis.  As it was I was lucky to get the pile built before the snow prevented me from accessing the location.

The bin is inside a large greenhouse.  It's sheet metal roofing in a 8' diameter circle and the bin is 8' tall.  I was able to fill it about 6' high with mostly fresh wood chips from the city.  At the bottom of the pile I coiled a perforated drain pipe with an inlet from the room to let air in under the pile.  At the top I capped the bin so it is moderately air tight.  I also have a 4" duct exiting the top and connected to a radon fan (relatively strong fan).  

The wood chips were mainly fall clean up branches.  There was a decent proportion of pine and minimal cedar/arborvitae.  Lots of the branches were pinkie diameter and had green bark on them.  The chips were generally the size of a pinkie finger chopped into thirds (sorry for that visual).  Of the 6 trailer loads we collected, 4.5 of them were fresh, 1.5 of them were springtime chips that were partially broken down.  Sometimes the pile we collected from was starting to warm up from being chipped recently.

The chips were a bit damp.  If you buried a paper towel in the pile it would become damp but probably not wringable.  As we added the 10 cubic yards of chips to the bin I added about 120 gallons of water.  I have no idea if that was the right amount.

4 days after building the pile, steam started rising from it and spots were heating up.  I finished the cap on the bin about that time.  Since then it's been a week and the pile hasn't gotten any warmer.  In fact, it seems to be cooling down based on the temperature of the side of the bin.  Today I opened up the door and looked inside.  Everything is damp and it's warm inside but not hot.  Probably in the 70s.  The greenhouse is around freezing inside in the morning and warms up tremendously on sunny days.  I want the compost to start providing heat before it freezes itself.

I have the radon fan drawing air through the pile for an hour a day.  It pushes a fair bit of air out of the bin but most is from leaks.  A small to modest amount of air is entering the drain tile under the pile so some air is drawing through the pile.  The hot/steamy exhaust travels through a grow bed and likely condenses out a modest amount of water.  This is water I'll need to replace into the pile so it doesn't dry out.

My main variables are how often and how long the fan operates and how much more water I add to the pile.  Today I changed the fan to stay on for 3 hours a day.

Hopefully I explained my situation, does anyone have any ideas?
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Jean Pain did tons of work using wood chips to heat his home.

I have collected many links about using wood chips for heat.

https://www.pinterest.com/mart85yahoocom/jean-pain/


But when I did my experiments I found that keeping the moisture and air ratio right helped alot, as well Jean pain spent much time compacting the wood chips.


The links I provided above will show you new ways of getting them to have the proper ratios.

Cheers.
 
Mart Hale
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This one especially good ->

https://youtu.be/cvMi6hgfcnw
 
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Mike, it looks damp enough, and I think you are probably getting enough air.  My guess would be not enough green.
 
Mike Jay
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Thanks Mart!  I don't have a pinterest account so the direct link is nice. I'll watch that tonight.  I read Gaelan's book as part of my research but I should check it out again and make sure I'm not missing anything.  

My pile is like Jean Pain only a bit smaller and inside and doesn't have water lines in it.  The hope was for the hot block of material to radiate enough heat to help the greenhouse out.
 
Mike Jay
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Thanks Trace!  I know for "proper" composting you need a lot of green to go with the brown.  For Jean Pain style it's mainly wood chips.  I believe Jean used summer trimmings which included leaves and bark which would have been some "green".  Mine has plenty of bark and some pine needles.  I didn't want to add too much other material (hay, manure, leaves, grass) since they can block the air flow and Gaelan recommended against it.  

But...  Jean Pain style reportedly gives you heat for 18 months and I only need it for 5 months.  So if I could add green in some manner that avoids blocking air, it could be the best of both worlds.  Maybe next year I could build the pile with spots or plugs of greener material surrounded with wood chips so the air can still flow through the chips.  Oh well, I have 10 months to figure that out
 
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Jean Pain was a forester and wanted to find a use for precommercial thinnings to make forestry really beneficial instead of only at harvest. His work enabled him to do that, but today we know a 50/50 percent mix of brown (wood) to green (grass) cooks the best. I think while you used "green" it was still on the nitrogen side of things and not protein which is why it is not cooking.

On the dairy farm, we did everything in our power to stop composting as it ruined the feed for the cows, but in the middle of the winter we could barely keep our hand in the pile of 100% grass or 100% corn. It was still great feed, but a nice warm meals for the cows.

With a mixture of grass, manure and snow, just mixing it inadvertently I have got visible flames from my sheep manure piles.


I have got straight piles of wood chips to cook, but it took tons and tons of it to do (think tractor trailer truck here)
 
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If you wanted to know in short order if it's a nitrogen issue, perhaps try adding some. Pee in it, or dump coffee grounds, or add some other nitrogenous amendment you have that has a proportionately high surface area.

If that fixes it, you'll know that the nitrogen in the largely ramial wood chips isn't enough, or isn't available to the extent necessary to generate the temperatures you want.

I would take equal parts sawdust and spent coffee grounds in a 5L pail and add urine, topping with water to make the mixture mobile within the chips. The higher surface area might kickstart the hot compost process, breaking down more material with locked up nitrogen, feeding the thermophylic bacteria and generating heat.

-CK
 
Mike Jay
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Travis Johnson wrote:With a mixture of grass, manure and snow, just mixing it inadvertently I have got visible flames from my sheep manure piles.


Visible flames I can do without  I've been trying to avoid manure so that I keep ammonia from building up in the greenhouse.  I know some compost heater folks have made biofilters to filter out the ammonia but I don't want to have to bother with that if I can avoid it.

Chris Kott wrote:If you wanted to know in short order if it's a nitrogen issue, perhaps try adding some. Pee in it, or dump coffee grounds, or add some other nitrogenous amendment you have that has a proportionately high surface area.


I forgot to mention that I did bury about 8 gallons of coffee grounds in the top of the pile before putting the cap on.  I just dug a hole and dumped it in to have a hot spot in the top center of the pile.  I don't know if it did anything but it does make the greenhouse smell like coffee.  I get 5-10 gallons of coffee grounds a week from my coffee shop.  I could mix that into 20 gallons (or more?) of water and dump it on the pile.  Think that would be worth a shot?
 
Mart Hale
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Mike Jay wrote:Thanks Mart!  I don't have a pinterest account so the direct link is nice. I'll watch that tonight.  I read Gaelan's book as part of my research but I should check it out again and make sure I'm not missing anything.  

My pile is like Jean Pain only a bit smaller and inside and doesn't have water lines in it.  The hope was for the hot block of material to radiate enough heat to help the greenhouse out.



Ya you really don't need a Pintrest account to use the links just double click on my link then click on the various links from there....

Glad to help.


Mart
 
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Coffee water will work great for adding nitrogen and even some fungi (will help both the wood break down and the bacteria thrive and move about), and it won't clog up air channels which will help the pile heat up.
As the chips begin to heat and break down, you might find you need to add air from the bottom up (pipe and air hose will do that pretty easily).

Redhawk
 
Travis Johnson
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You need hay...nothing else.
 
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Coffee water will work great for adding nitrogen and even some fungi (will help both the wood break down and the bacteria thrive and move about), and it won't clog up air channels which will help the pile heat up.



Mike, I second this. I get coffee grounds from work maybe a kilo a day, let them sit in the garage in a bucket for a week until it's full (might need to be indoors in your temps), and then dump them on the chips. I think it's a matter of kick-starting the microbes, since they aren't very active in the cold. I think you got set back by not having it in place for a few weeks before the cold (but I know you were busy with the greenhouse). I do think it will work, but the C/N ratio favors fungal decomposition and they are slow growers.

I would't worry about ammonia from urine in that pile, unless you are a dipsomaniac on lasix. I have entire deer skeletons buried in my piles. I get them from a taxidermist by the trailer. There isn't even enough smell to bring in the opossums or dogs or coyotes. I got that from Joel Salatin, btw, I'm no genius. Not paying for calcium again my friends!!!
 
Mike Jay
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Thanks for the Mother Earth News link Mart, I hadn't seen that one before.  Here are a couple quotes that are very interesting:

M. Pain claims that a cubic yard of brush can, under ideal conditions, absorb and retain about 140 gallons of water if the pile is progressively stacked and soaked over the course of three days.  


That would suggest that I should put a whole lot more water on the pile.

Jean prefers a cutter that produces slivers rather than chips . . . since water penetrates the surface of a long thin fragment more easily than it does blocky chunks. Though the shavings may be as much as an inch long, the ideal thickness is about 1/16 of an inch.


I can't do much about this but I'm glad my city's chips are somewhat smaller than just chunks of wood.

Travis Johnson wrote:You need hay...nothing else.

 That's great to know.  I am in forest country and hay is expensive though.  I think round bales are $45 and for loading the bin I'd probably need small squares.  Wood chips are free for the hauling on the other hand.  But if I run across a source of spoiled hay (or straw?) I'll keep this in mind.

Bryant RedHawk wrote:Coffee water will work great for adding nitrogen and even some fungi (will help both the wood break down and the bacteria thrive and move about), and it won't clog up air channels which will help the pile heat up.
As the chips begin to heat and break down, you might find you need to add air from the bottom up (pipe and air hose will do that pretty easily).

 Thanks Bryant, that's great to know.  The older chips that are mixed in did have some mycellium started in them.  I'll dump all the coffee grounds in there with lots of water.  I do have air inlets underneath and a fan to draw so I "should" be all set there.

Tj Jefferson wrote:I would't worry about ammonia from urine in that pile

For clarification, I'm not worried about ammonia from a bit of my urine.  I'd be worried if I used, say, 40% horse bedding/manure and 60% wood chips.  Or some other mix that had many hundreds of pounds of manure/urine in it.

Thanks for all the replies everyone!  I'll watch the Gaelan Brown webinar again tonight for a refresher.  I think I need to add more water and I'll add coffee grounds to the water because it can only help.  I'm getting about 8 gallons of grounds a week and I know where I'll be putting it all winter.  Now I wish I had the well working in the greenhouse.....
 
Mike Jay
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Just rewatched the webinar and it sounds like I also need a lot more air.  On their commercial rigs they aerate full time or at least half the time.  That's on bigger piles but their fans are probably also working better than mine.  I think I'll ramp up the air more after Thanksgiving.  I could replumb it so that the fan is pushing air into the bin under the compost and then out into the grow bed.  Downside would be that air leaks in the bin would let compost gasses out into the room (if there are any).
 
Mike Jay
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Ok team, I'm back with an update.  

My first test was to pump coffee grounds and water onto the pile.  Lesson learned was that coffee grounds don't like to be pumped.  After swearing a bit I gave up on that and moved on to adjustment #2:

I suspected that I wasn't getting much air sucked through the pile from the top so I redirected the fan to blow air under the pile and up through the chips.  Up side is the air is definitely going though the wood chips.  Downside is that air leaks at the top of the chamber may/will let air escape instead of going though the planting bed.

Also, based on the webinar, I turned the fan on for 12 hours a day.  I did this for about a week and saw no improvement.  I think the pile has been cooling off and now it's not very warm at all.

During all this time, the outdoor temps ranged from 20-35F as a high and 15-20 as a low.  The interior temps ranged from low 30s in the morning to the low 40s by the afternoon.  Coincidentally this has been the cloudiest November I can remember.  I think we've had two mostly sunny days and two slightly sunny days in the last 4 weeks.

Today I got more coffee grounds and dove in again.  Since more air wasn't doing the trick, I turned it down to 2 hours twice a day.  I opened up the door and checked things out.  The surface of the chip pile was very damp, the ceiling was dripping and the temp was cool inside.  I dug a hole near the door (5' off the ground) and hit pockets of obvious dryness.  I put in 12 gallons of coffee grounds and about a gallon of chicken poop and mixed it up with some of the wood chips with a pitch fork.  I covered it up with wood chips and then poured about 25 gallons of hot water on that spot and the surrounding 3'.  My hopes are to:
  • matriculate some of the coffee grounds down lower in the pile
  • add moisture and heat to that section of the pile
  • melt the frozen chicken poop with the hot water
  • Hopefully kick start a biological reaction in that spot that spreads to the rest of the pile

  • If this does get the reaction started, I'll need to add a lot of water to the rest of the pile.  The only water I have in the greenhouse now is 34 degree stuff in some barrels.  I don't want to add that until there's enough heat to overcome the cold water.
     
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    Chris Kott wrote:

    pee in it

    Yes... just ask my husband. He complains because he's got the better plumbing for peeing in a bottle than I do, so he fills the bottle just less than 1/2 full of water, pees in it until it's full and we pour it on one of our several wood chip piles. As Mike Jay has said, we too are in an area where getting wood chips is cheap or free, but hay is pricey and hard to get. I wish I had a reliable source of coffee grounds, but I do have one restaurant where they save their veggie prep scraps (onion bits, cabbage cores, some fruit skins etc). I find it does a much better job of heating the pile if I dig a hole and drop a bucket full in and then cover it.
     
    Mike Jay
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    I could pee in it too.  Seems like a piddly amount when compared to the gallons of coffee grounds I get every week.  I just started getting a couple buckets of organic cafeteria scraps (organic!!!) a week and I could put them in as well.  Did I mention organic?  

    I do pee on the garden compost pile in the summer because it's at a more convenient elevation.  The current wood chip compost pile is 6' high, under a 8' high ceiling and through a door so I'd need a ladder and some bendy skills...
     
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    Fresh Raminal Woodchip is the way to goo next time C:N ratio is about 40:1, So very little work need to balance it.
     
    Mike Jay
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    Thanks S, what exactly are "raminal" woodchips?  The ones I can get for free come from the city and I believe are chipped up fall shrub and tree prunings (smaller diameter).
     
    Trace Oswald
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    Ramial wood chips are just chips made from branches 2" or so and smaller.  They are the right proportion of green to brown.  If you get your chips from the city, and I do as well, you just get what you get.  I nearly always need to add greens.  I get quite a few leaves and pine needles and things, but the ones I get always of pieces that clearly came from bigger stuff as well.
     
    Mike Jay
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    Thanks Trace!  Then I'm guessing the majority of these chips are ramial.  I don't actually know where the city gets them.  But I'm collecting them at the same time of year that the residents are putting out their leaf bags and piles of prunings at the curb.  So I "think" the city crew is driving around and chipping up those trimmings and piling them in the lot where I grab them.  They might be cutting down larger trees in parks or right-of-ways but I'm thinking they'd be doing that in the late winter instead of fall.  Mainly because they have enough to do with leaf bag collection and pre-winter work.
     
    Mike Jay
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    I opened up the door/hatch and had a look inside today.  It was warm where I put the poop and coffee grounds!!!  I stuck my crappy compost thermometer in the spot and it read 70.  I think it's off at room temperature so it's likely closer to 80.  In a day or two we'll know for sure.

    If that did do the trick, my plan is to haul hot water out there again (6 five gallon buckets or so) and wet down an area next to the hot spot.  That would hopefully warm it up from the current temps in the 30s and encourage the biological activity to spread into that warm/moist area.  

    If that works, lather, rinse, repeat
     
    S Bengi
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    You might not need all the water that you are adding.
    Also the compost turn the scraps into carbon dioxide and water, you will even see it steaming after awhile. So it will start to water itself. I am not physically there so I can't tell if your compost is wet enough or not, but I had to guess I would say it is wet enough
     
    Mike Jay
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    Thanks S...  I should have started this by saying that anyone with experience is welcome to come out and troubleshoot it in person

    I have two reasons behind my worry that it's too dry.  One is that Jean Pain apparently used up to 140 gallons of water per yard of chips.  I used about that much for 10 yards.  When I loaded it, it was lightly damp but not wet.  If I had buried a paper towel in with the chips and took it out a minute later I wouldn't've been able to squeeze any water out of it.

    The second reason is that yesterday when I started digging to make this little spot, I hit several spots that were dusty/bone dry.  It's hard to tell how much of the area was dry vs damp since the chips kept falling in as I tried to dig with the fork.  

    One compounding factor is that this pile isn't outside.  And I'm actively pushing air through it.  That air is coming out the other end of the grow bed at 100% humidity.  And, assuming the air is a bit warmer than the bed, it condensed some water out on its journey.  So I suspect that those actions are drying out the pile more than it would experience outside.

    But this is mostly conjecture.  If I was smart enough to make a video, I could post that and then we'd get it figured out right away
     
    S Bengi
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    I was worried that with it being winter/fall and you adding water it would dampen the process. But if it bone dry, in certain spot (or dusty looking spore/fungi) then watering sounds like a very very good idea. Sounds like improvements is happening with the extra nitrogen, and hopefully it keeps on getting hotter.
     
    Mike Jay
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    Ok, I have an update.  The coffee grounds and chicken poop spot heated up to 110 over the course of a few days and then started cooling off.  When it was around 100 I brought out 6 five gallon buckets of hot water and poured them on the pile around the hot spot to try to get it to spread.  So I think I can say that the area by the door is well hydrated.

    Yesterday the hot spot was down to 80 on the thermometer (likely 90 in real life).  I had more coffee grounds so I dug two more spots (on either side of the door) and mixed in 4 gallons of grounds in each spot, covered them up and poured 4 gallons of hot water on each spot.  Overall I think I've dumped 45 gallons of hot water in this general area by the door (4' by 2')

    To better contain the air/gasses when the fan blows, I raised the top off the bin and slid in a layer of poly plastic.  So now when the fan comes on the poly inflates a bit.  So I know air is coming up through the pile.

    So where does that leave us...  
  • If too little water is the problem, the part of the pile near the hatch should be showing results.
  • If too little N is the problem, the coffee and poop should do the trick.  It did heat up for a couple days and then tapered off to 90 so maybe that's a win?
  • If too little air is the problem, 12 hours a day (introduced under the pile) should have done the trick
  • If too much air is the problem, I've turned it down to 1 hour a day and we'll see if that does it
  • Maybe I'm only getting air around the perimeter and it's not going up through the core of the pile?

  • I'm not sure how to tell if the air is coming up through the middle of the pile.  The surface is wet so I can't toss pieces of tissue in there to see if they are lifted.  I might get an incense stick and see if I can see the smoke getting blown by air.  But smoke rises anyway so it may not be a good measure.  Does the team have any other ideas?
     
    Tj Jefferson
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    Mike,

    This is really interesting. I have been looking at doing a chip-heated greenhouse and you are doing all the hard work! Quick question, what is the temperature of the water you are using on the piles? I am assuming this is brought from the house at groundwater temperature, just want to confirm.

    Just observational- I have about four giant chip piles. Each are about 20-30 yards of material. I've tried to get them as high as possible to increase thermal retention. Each is a different age or type of material.

    The only one that is routinely steaming in the morning is the one that is the most fluffy, woody mix. Ironically it is also the smallest! This speaks to the aeration requirement, this one is still getting oxygen internally I think. The only other permutation that seem likely is that it has been wet here, like 18" of snow and then an inch of rain in the last weekish. The one that is doing the best is higher in elevation and drains to the others. I suspect the cold water is absorbing heat in the other piles.

    One thing that I believe to be true is that decomposition generally produces water (hydrogen from breaking C-H bonds plus atmospheric oxygen). I don't think I need more moisture than what is produced. So I think I will tarp one of the piles and see if I can prevent thermal loss, and just allow the condensation to return to the pile. This will decrease the available oxygen, but prevent cold water from getting to the interior.

    One of the other piles I am going to turn today. This should help the aeration. I am thinking of drilling holes in PVC pipes and shoving them toward the core of one pile to add oxygen. I suspect there is a thermal loss going on there from air being pumped through your piles, and I'm a little concerned that 12 hours of (effectively) active cooling in the center would be way too much, and even two hours a day might be pushing it. That is why I am aiming for only passive air movement, it should gradually warm as it is drawn in like your nose warming up air before it hits your trachea.

     
    Mike Jay
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    Hi TJ, it's my pleasure to be running this experiment :)

    I think the lofty/shredded aspect of your "good" pile sounds very similar to the wood chip texture that Jean Pain was using.  Per the Mother Earth news article linked above, his pieces sounded like they were the size/shape of toothpicks.

    The water I've been hand hauling out to the greenhouse is domestic hot water.  So about 140 degrees.  Whenever I get a delivery of free organic food scraps, I wash the buckets out and that becomes the water for the compost experiment.

    That's neat that the chips may produce their own water.  As long as I don't blow too much of it away, that would really work out nicely.

    The reason I think I need to force the air through the pile is that it's only 6' high and the bin is capped so air can't rise off the pile and exit.  It's capped so the stink/gasses/humidity will be contained and able to be sent through the grow bed for heat.

    Before I got the cap on the bin the wood chips were heating up and steaming.  This was when the pile was a couple days old (freshly aerated).  The steam was condensing on the greenhouse walls so that's another reason to contain it.
     
    Bryant RedHawk
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    hau Mike, do you have holes in the heap?  I'd use a piece of 3/4" pipe to punch holes in at around a 30 to 40 degree angle that should let more air in, you can also punch hole down in the middle area for air flow.
     
    Mike Jay
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    Hi Bryant, I have a 4" perforated drain tile coiled under the pile that the aeration fan now blows into.  The sides of the bin are roofing tin and the top is poly sheeting.  There's a 4" exhaust line from the top that goes through the planting bed before it exhausts back into the room.

    The access is only through the door/hatch so I could poke additional holes from there.  I'd probably have to hammer a pipe in.  Are you saying to punch the hole with the pipe and then remove the pipe or leave it?  

    Maybe I could find something to make the hole with that isn't round.  Like a 1/2 by 2" bar.  Then once it's stabbed down into the pile, I could put a big lever on it and give it a twist or two to loosen up that channel in the pile.
     
    Bryant RedHawk
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    yes punch the hole and remove the pipe, and since you have drain tile at the bottom, try not to hit it with the pipe.
    A pry bar would work just as well and I like the idea of using it like a pry bar once down in the heap.

    If the coffee grounds got the heap to get hot and since it cooled again, just add more grounds.
     
    Mike Jay
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    Gotcha, thanks!  And yes, the coffee grounds did heat up that spot (2' sphere) but I need the whole 8' cylinder of chips to heat up.  Maybe with punching holes I can figure out a way to push coffee grounds down into the pile.  

    Oh, I know.  Take a 2" pipe.  Weld something to the side of it to make it "not round".  Fill the pipe with coffee grounds.  Cap the end that I'll hit with the sledge hammer.  Drive it down into the pile most of the way.  Twist, rock, pivot to loosen that spot.  Take the cap off and put a smaller pipe or plunger into the 2" pipe.  Pull the 2" pipe out of the pile while pushing on the plunger.  Goal is to leave the coffee grounds in the hole as the pipe is removed.
     
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