One thing I've noticed in my several attempts so far at a hot batch of compost in my Mantis ComposT-Twin is that as the materials in the tumbler reduce in volume, they get wetter and wetter, as indicated by the substantial amounds of the dark water that drips out of the tumbler into the catch buckets that I have below mine. I suppose I could add some shredded newspaper, dried grass clippings, or something like that to absorb the extra water. But it seems to me that if I add paper or grass clippings, that I'm basically starting the load back at the beginning in terms of having materials in there that are back at the beginning of the composting process.

What I'm trying in this batch is to add only water or lawn fertilizer, if necessary, to keep the batch hot. And I'm only turning my tumbler if the center temperature is below 100 degrees F or above 150 degrees F.

Jim

I wouldn't, after a heat cycle I put the material into a curing bin for finishing and start a new batch.

"How can you be sure your compost is finished?"

There are respiration tests that can be done but for a home composter it probably is not worth the cost. Try the bag test and a seed germination test.

You are not likely to tie up nitrogen based on the description of your procedure/materials. Nitrogen deficiency usually happens with high carbon materials being incorporated (mixed) into the soil.

This is an old thread but it has some good information.

Here is a thread that talks about using unfinished compost and some of those issues.

Lloyd

1) Ingredients not recognizable any more
2) Dark brown color, almost black
3) Earthy smell only

Compost is not considered done when the hot stage is completed. I sometimes use it at that point, but only because I'm in a rush to start the next batch.

There have been a number of threads on whether compost needs to be 'cured' or not. Those who write papers and books on the subject use 'cure' differently than some people in the Compost forum. They say 'mature', 'cure' or 'stabilize' for the period of mesophilic breakdown. Experts say there are either two, three, or four stages of the composting process. Cornell says a one year period is best for curing; my book "Easy Compost" says at least thirty days.

Without agreement on the basics; some will try to sell you on making compost in 14 or 30 days. My outdoor mesh bins, make a decent compost in three to six months, with a hot stage in the beginning.

I suspect with a bin that large it should have sustained a temperature of 130+ for at least three to four weeks if all the conditions were in the optimal range. If it didn't, then one of the parameters was out and it could very well be the C:N ratio.

Lloyd

When I started my first bin, the internet searches I came up with said 75/25 leaves to grass. But I don't think that is the right ratio for my leaves. In my newest bin (3'x 3'x 3') I am now trying 50/50. But it is very hard to determine whether I am getting 50/50. Leaves are very finely shredder and grass has not been shredded because it clogs the shredder. So today I tried measuring the leaves vs grass before the leaves were shredded. Maybe that will work.

Unfortunately I have not yet purchased a compost thermometer. I am using a tomato stake with a metal core and plastic on the outside to determine if the pile is still hot. There were to many brands of thermometers and I just gave up trying to figure out what was a good brand to buy. Any suggestions.

There can also be issues with using very finely shredded leaves in that it may inhibit air infiltration into the pile. Some coarseness is good to increase the porosity of the pile.

As far as heat goes, for the first few years I just used a steel bar as my temperature probe. I left it in the pile and just pulled it out to take the temperature. If I could brand cattle with it it was too hot. If it was too hot to touch at all, probably over 150F, if I could grasp it for a few seconds I guessed around 130-150 depending on how long I could hold it. When I could easily hold the bar it was under 110. Of course this wasn't exact but it was fun to show people. I now use a 20 inch Reotemp to monitor the temperatures.

Lloyd

1 pound of dry, finely shredded leaves to 1.5 pounds fresh grass clippings.

'Dry' in this case means as they fall off the tree, and for the next few weeks, without any additional water such as rainfall.

You could substitute Starbucks used coffee grounds for grass (they give you the expresso grounds which have more water than the other grounds you can find in the dumpster).

I used a digital bathroom scale to weight trash cans of shredded leaves and shredded grass. The coffee grounds I weighted in a Rubbermaid container. The following year I had an good idea of what the ingredients weighted, and just went by eye, or went by trash can volume.

On the issue of adding versus not adding material, I have no steadfast rule. I try to mix up a large enough pile to retain heat on the first day. A four foot diameter pile two feet high is a nice size for piles containing mainly leaves as the 'brown'. Since I was informed one could not have ten small compost piles (there was not actually any limit on the number of piles in the regulations), I switched to a rectangular size for my two piles. Four or five feet by eight or nine feet long, two feet high.

If material is added after the pile is first constructed, it is usually fresh-cut grass, which breaks down quicker than most ingredients. If fruit/veggie wastes, or fish parts become available, they are added to the core (hot center part), IF THE CORE TEMP. IS 130F OR HIGHER.

The most overlooked factor often seems to be particle size of the ingredients. Smaller is better, at least until you get down to fine sawdust size, which may cut off air if the pile is too large. Browns consisting of sawdust, shredded leaves and large wood chips would not compost at the same rate.

I've used pine wood chips that are sold in square bales as horse bedding, because I found broken bags in the dumpster. :-] I'm too cheap to pay for browns.