Compost baking

Miniture compost test piles

This week I made a mini-compost pile in the kitchen. Why?
The aim is to create a compost test pile, to check that my ingredients will work well for a larger pile, so I can use my time, effort and materials wisely.

I wanted to see if the temperature would rise enough to know that the high-nitrogen material is effective in raising the temperature of the planned large pile to kill any potential weed seeds and pathogens that might be present.

Making a mini compost pile is fun, particularly on a rainy or not quite snowy enough February day! Just measure your ingredients in cups rather than in buckets. It reminds me of cake making by volume (ever made a 3-3-1 cake?)

Here is a recipe suitable for kitchen compost: 6-3-1.

If you fancy trying your own recipe, just be meticulous with the cleaning. Compost baking tools are only for compost, probably goes without saying.

6 cups browns, which can be a variety of materials. I used 1 cup each of:

  • Leaves
  • Hedge clippings
  • Wood chips
  • Cardboard
  • Seed heads and stalks
  • Straw mulch

3 cups of greens:

  • Compost (it can be confusing to talk about greens, as it’s not just about colour, but more a classification of the carbon:nitrogen ratio in the ingredients. This one came from just green weeds).
  • Veg and fruit peelings

1 cup of high nitrogen material:

  • Chicken manure (organic- routinely used antibiotics would kill our lovely microbes)

Water:

The best would be rain water.
I was using municipal water, so checked what my supplier was using for treatment. If it’s chlorine, it can just stand for at least 24h before use, ideally in a wide-mouthed container, and it will “gas off”.

My supplier uses chloramine, which is more stable in water. The recommendation is to use humic acid to neutralise it before using it in compost making. That’s what I had to do. I soaked some of my mature compost, which contained humic acid, in the water.

With this water, I soaked the “ingredients” (each group separately, so they don’t start reacting too early) for about 20 hours.

Then I mixed it up all together, checked the moisture levels were right, and stirred it around with a big wooden spoon.

And here is the assembled mini compost “cake”:

Mini compost test pile

I want there to be sufficient air flow, hence I left an air gap. I also covered the construction with a plastic bag, similarly to a tarp covering the pile outdoors to keep the rain off. In the kitchen, it was more to keep the moisture in.

And then I was hoping that temperature in the middle would get up to 37-49 Celcius (100-120 Fahrenheit) in 48 hours. It doesn’t need to be quite as hot as a “proper” sized compost pile due to it’s small size. But it is enough of an indicator whether my nitrogen supply was strong enough.
This one was “underbaked”:

Mini pile: 20 Celcius

The pile managed to get up to temperature a very little: 10-12 degree above ambient temperatures within the first 24h, and stayed there for 5 days, still counting.
What does it tell me for a large pile?? I am not 100% sure. I understand I need more of the high nitrogen materials to get the pile up to temperature in this cold weather. But how much? Only experimentation over time might help me develop a formula and/or intuition.

I also think the compost should count as a “brown” ingredient, even though it came from 100% fresh green weeds.

A look under the microscope revealed lovely nematodes, at least 2 species – 14 in a single drop, and plenty of amoeba. Though only 2-3 morphologically different ones, so could do with more variety. Wonder how this will develop over time.
With approx. 543000 amoeba/g; and 2800 nematodes/g nutrient cycling is happening. But fungi still nowhere to be seen to be statistically countable, though some are there. Let’s wait and see how they develop. It’s early days for them.

I’ll try batch 2 with more chicken manure, but will also try another high nitrogen material.

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