Closed bin compost collecting water at the bottom

Question

I have a closed-bin compost bin (because of location/equipment, I don't have anything open and I can't tolerate the smell). My compost is almost entirely greens, now black and rotting (I didn't put enough browns).

Even though I'm starting to add browns, what confuses me is the water quantity. I put fresh greens (eg. orange peels) every day or two, and every time I look, I can see the bottom portion of the bin has liquid in it. I can see the liquid in it.

I'm trying to compensate temporary by adding more browns (shredded newspaper, dried-out weeds), but is there a deeper problem here? Is this normal to see water collecting at the bottom of my closed bin?

(It's a ~13 gallon dark blue plastic garbage can that I leave outside. I can move it into the garage if indoors is better for composting.)

Answer 1

Green plant material contains a lot of water that is released as it decomposes. The liquid in the bottom of your container is called "leachate". You can try drilling or cutting some holes in the bottom of your container to let the leachate drain out.

You need to add browns. Greens have more water and the nitrogen makes them compost faster. If you don't have enough browns you can try letting some of your greens sit out in the sun for a couple of days so they brown out before adding them to your bin.

Composting also needs air. If the compost bin doesn't get enough air the composting becomes anaerobic and starts to smell. If you insist on using a closed bin you should turn it to aerate.

Answer 2

It is ironic that closing up your compost because you don't want the smell is precisely what is causing the smell. You can compost in just a heap - a little pile of stuff in the far corner of your yard. If you want to confine things a mesh walled container with no floor lets air in and liquid can drain away. If you are worried about varmints, a mesh or slatted lid can keep them out.

At a minimum, make a bunch of holes in your garbage can - in the bottom to let the liquid out and in the sides to let air in. Aerobic composting smells musty and earthy. Perhaps not entirely pleasant (it's not like chocolate, coffee, baking bread, fresh roses) but not disgusting. Our bodies reserve disgusting for anaerobic decomp - sliminess, sourness, acrid smells. So if your compost smells wrong, get more air to it.

The other thing with composting is to ask yourself why you are doing it. Are you trying to make fertilizer for a garden, or to reduce the amount of garbage you send to the landfill/incinerator? Which is the primary motivation? If the latter, don't get too worked up about greens/browns, balancing things, adding stuff just for the sake of the composter etc. In our mesh bins (scaled down versions of the bins from the Victory Garden book) we put peelings and the like from the kitchen, carrot greens and other parts of plants we don't eat, weeds we have just pulled, and fireplace ashes when we happen to have emptied the fireplace, all without a plan: just as stuff becomes available, it goes in. We have never (20+ years) measured its temperature or chemistry in any way, unless you count smelling it. The only turning we do is that described in the book - you take compost from bin 3 whenever you need it, and when bin 3 is empty or bin 2 is full, you turn 2 into 3. Meanwhile when 2 is empty or 1 is full, you turn 1 into 2. 1 is where you add new stuff. Sometimes we toss a little dirt (or bin 2 or 3 contents) over the top of 1 if it's smelly.

This super hands off approach works great for us. We get compost for rhubarb, the veg garden, and the flower beds. We throw out almost no garbage. And we don't fuss about our compost. If you can adopt something similar, I think you will prefer it to a single closed bin that needs babysitting and looking after.

Answer 3

Here is where some of the water is coming from

C6 H12 O6 (organic matter) + 6O2 ---> 6H2O + 6CO2 + energy

Browns would slow the breakdown process, giving evaporation a fighting chance at reducing water accumulation.

Here is where the smell is coming from

C6 H12 O6 ---> 3CH4 + 3CO2

Without oxygen, you get methane (CH4), which stinks. Browns would slow the breakdown process, therefore requiring less oxygen per hour. Browns would also increase "fluff", absorb moisture, and let the pile breathe more.

How often to turn the pile?

According to their experiment, microbes can strip out the oxygen in compost within 15 minutes, there must be a constant flow of air through the compost, and far more than provided by passive aeration by convection.

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It's been well established that most of the oxygen added to a pile during turning is used up by the microbial populations within hours, or even minutes of turning. Therefore, unless additional oxygen is being provided under pressure (ie. via "forced aeration") or a pile is turned hourly, the purpose of turning is NOT to add oxygen but rather to restore pile porosity which allows oxygen and carbon dioxide to naturally move into and out of a pile through a process called "passive aeration".

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