Compost not hot

I started with a compost tumbler last November.  I've been adding stuff all winter, and it has yet to get warm.  Most of what I add is kitchen scraps: vegetables, egg shells, and coffee grounds.  I fill up about a gallon a week with these scraps, and dump them in the composter.  I have a pile of mulched leaves and grass from the mowing last summer that I keep next to the composter.  Every time I dump in the kitchen scraps I add a handful or two of the leaf/dead grass material.  I first filled the left side of the two-bin composter, then started to fill the other side and let the first side cook.  But very soon I realized there wasn't enough material in the left bin, because it compacted down after a while, so I began adding to it again until it was fuller, then stopped and filled the right side.  Both sides were about full, but the material doesn't seem to be doing anything; there has never been any heat or even warmth in it.  I can't recognize individual items anymore, except eggshells, so I guess it's breaking down some, but how long should it take? Will it eventually compost even without heat? Should I do something different?  I'm not sure how to "end" filling a bin, because we keep making scraps and I have to put them somewhere, so I keep adding them.  But five months later I have no useable compost. . .at least it doesn't smell.

It takes a mass of moist material to generate a hot compost. A gazillion little microbes working away producing heat from their activity. Hot composting is good in that weed seeds and disease and insects are killed. Hot composting is around 140-160*F.

A small mass can't build up heat. But it can compost over time as you are finding. Once a side has been filled, don't keep adding more material. Yes, the volume has shrunk in half but that is just the process. The clock starts all over again each time new material is added. It may be that you actually produce an unusual amount of kitchen waste and could benefit with a compost cage, like 3'x3'x3', or more (and larger) tumblers.

It is recommended that home compost be sifted with a 1/4" hardware cloth screen. The larger, not-composted material can go back into the composter with more material for a second round of composting. PS Even some commercially bagged composts have a lot a un-composted material and benefit from screening.

Thank you, Sanderson! That makes a lot of sense, and assuages my doubts. Perhaps I do have useable compost in one side; I'll sift it and add the big stuff back.  I'm not ready to set up a bigger, unmovable bin so I'll just keep on with "cold" composting for now.  I didn't realize the heat is a function of mass. 

However, I do realize I'll never create enough compost on my own for mixing Mel's Mix! But I should have enough to add to my existing boxes when replanting. Good enough.

OhioGardener wrote:Compost tumblers can and do make good compost at a fairly high temperature without a large volume. I have two Jora JK-270 twin compost tumblers which have a volume of approximately 35 gallons per side -- that is equivalent to an average galvanized garbage can -- and each side easily heats to 140ºF to 160ºF after filling with well balanced C:N material.

You are correct.  I had an 80-gallon tumbler and would fill it to the top with various browns and greens and water and it would take off.  You fill the units in one sitting, correct?  That will allow heat to build up.  Adding material over time doesn't seem to allow for "lift off".

Do you have a compost thermometer? They are very helpful in knowing exactly what is happening in your compost.

 Yes, invaluable for serious composters.

Composting is a life-long learning experience. Robert Rodale got me started with composting in the early 1970's, and I have been doing it every year since. But, I'm still learning what works and what doesn't work with composting.

When I check the condition of a newly filled section of the compost tumbler, I find it hot and in need of turning.

Nice!

OhioGardener wrote:But, the section of the compost tumbler where I add the home kitchen scraps is gradually filled as daily scraps are added. I periodically also add some pine pellets to balance the C:N ratio. During this prolonged period of time it will do some "cold composting", but will not heat up a above maybe 90ºF to 100ºF.  Once the section is totally filled it is left to begin final composting. At this time it will begin heating up to complete the hot composting process. I monitor the temperature every day or two and turn it when necessary. These sections of the tumbler take longer to compost than the ones that are completely filled at once

Probably this is what's happening with mine, since I keep adding.  Trouble is, the bin never really seems "full;" there's always room to add another bucket of scraps, so I think I keep the compost in the cold composting phase.  

I have to look up the proper ratio of green to brown, but I'm not really into doing a bunch of calculations every time I add material.  I tend to add two double handsful of leaves/grass (brown) for every bucket of kitchen scraps (green), and call it a day.  Maybe this is too much brown? Hard to know, but my material never gets smelly and slimy, so that's gotta be a good sign. 

I don't have a "composting" thermometer, but I have a digital temperature probe that works.  One side has a max of 64° and the other registers various temps in the 70's and 80's.  The colder side I am going to sift, and then I'll add the large material into the rest of the current batch, then stop adding to that side.  I'll see if it heats up when there's more mass undisturbed.

Hmmm.....I finally got around to "sifting" the one side of my tumbler that was ready (I thought).  A note in retrospect first: I always felt like the tumbler never really tumbled all the material when I rotated it.  The weight would feel as if much of it stayed in the bottom of the bin, while only some was tossed around.  I wasn't about to put my arms down in there to feel it to see, though. (A little bit of a gross-out factor there for me.)  Well, I think I was right.  I opened the bin today and tried to dump out the compost, but most of it stayed stuck inside.  I used a trowel to pry it loose, and I began to smell that smell as the "compost" fell out.  

Now I have a bin of wet, black, somewhat compost-y and somewhat slimy material that stinks. Not all of it stinks, actually, it seems to be only the stuff that was stuck on the bottom.  It's too wet to sift.  Temp before I dumped it out was in the low 80's, and I never smelled anything bad when I would open the bin to add material.  I never added water, either, except right at the beginning, because it always looked damp.  We have had over 4 inches of rain in the last week or so; perhaps that explains the wetness?

My preliminary diagnosis is too little rotation: I need to make sure the material is actually getting tumbled when I spin the bin.  Any other suggestions?

Should I let the current smelly batch sit out to dry, then sift it or should I put it back with more dry material to continue to cook?  I know the smell is due to anaerobic rotting, but I don't know how to fix it other than add more browns.  Should I be adding more leaves with each scrap batch?

The first picture is how the compost looked before I dumped it out.  The second is after I pried all the smelly stuff out.  Hard to see, but the stuff is WET.

P.S.  Also found many earthworms, flies, and a roach in the mix.

Maybe try adding dry leaves or bedding straw to the wet stuff, mixing as well as you can to give it another round in the tumbler.

Or, spread it out in the flower beds / tree areas.

Oh, that's a good idea!  Maybe I'll just mix it into the clay soil when I dig my next shrub bed.  I can work in the compost and let it sit a few weeks before planting in it.  

I think I have a better handle on the tumbler now.  I have to make sure when tumbling that everything moves.  I was surprised how much "compost" came out of one side of the bin, though; the compartments don't seem very large, but I got more than I expected.

Add water. compost should be  moist enough to hold together as a wad in your hand but not too much as to drip.  A moist sponge.