As I mentioned in my post a couple of weeks ago, one of this year’s projects on our urban homestead is perfecting our thermal composting method.
We’ve built some nice compost piles, hubs and I. And then there are those that we weren’t paying proper attention to, that we forgot to turn, that didn’t have the right proportions of woody and green materials, that never got quite hot enough. Yet as I learned in Elaine Ingham’s Soil Food Web course this summer, the right timing, the right temperatures, the right moisture are not tangential factors if you want to make good compost; they’re essential. And of course you want to make good compost if you’re going to do it. If you make bad compost — say, you let your compost go anaerobic — all you’re doing is creating an ideal habitat for the kinds of micro-organisms that make your plants sick. Properly made thermal compost really goes through all the right stages, making it a good habitat for the right kinds of soil life — the critters that, in turn, help your plants to grow.
So we’re going to do it right this time.
“Right” in the composting context means “right for the needs of your particular soil and what you want to grow.”
And so we need to learn to make two different kinds of compost, depending on our soil needs: fungal compost that encourages the growth of fungi in the soil, and bacterial compost that invites friendly bacteria. Some plants prefer more fungal-dominated soils, others prefer to have their roots surrounded by a bacterial-dominated environment. If you’re growing annual vegetables, or grass for grazing animals, you’ll want a more bacterial soil and therefore more bacterial-dominated compost. If you’re growing shrubs, vines, bushes, and trees — or plants like strawberries, whose natural ecosystem is a forest — you’ll want more fungi. Green = bacterial; woody = fungal. (You know how a pile of wood chips that’s been sitting for a while starts to develop those fine white strands of fungi? That’s a good rule of thumb: fungi love woody stuff.)
Therefore, to make a fungal compost, you simply put in more “woody” materials than “green” materials. Even though we’re using our compost for vegetables, many soil problems are due to not enough fungi in the soil. So the compost we built today is optimized for fungi.
Here’s my simple cheat sheet for the ratios for both kinds of compost. Feel free to print it, tape it to your composting bin, or save it to your handheld device if that’s what you’ll have in your back pocket when building compost!
A word on materials: when building a compost pile, you want to be able to make use of as many freely available, local materials as possible — the kinds of materials that might be labeled “waste” and thrown away, if you didn’t have your Golden Compost Goggles on. But you do, right? What a great opportunity to get to know your locale and start noticing streams of free resources! Keep your eyes peeled for things like cardboard boxes by the curb, piles of leaves that neighbors are throwing away, coffee grounds that your friendly Starbucks barista is going to just scoop for you for free. To give you some ideas, here’s what we built our latest pile with, with sources and costs:
- woodchips (free: call your local arborist or city tree service — and you might just wake up to this sight on the right)
- shredded cardboard (free: find anywhere)
- dried leaves (free: from our yard)
- straw (free since we already had it around for mulching)
- shredded paper (free: from my office)
- green grass clippings (free: from our yard, neighbor’s yard, and a vacant lot nearby)
- kitchen scraps (free: from our kitchen)
- coffee grounds (free: go to any Starbucks and just ask!)
High nitrogen materials:
- horse manure ($ 10 for a trunkful from a local horse owner)
- chicken manure (this time we paid $8 for a bag, but when we had chickens it was free)
- alfalfa (about $18 per bale at the feed and seed store)
Here it is! All of this got piled into our Geobin compost bin according to the ratios of fungal compost above. I used masking tape to make little marks on the outside of the bin to guide us in keeping the right percentages — although it’s not necessary to be scientifically accurate about it. Just guesstimate and relax.
Now the fun begins: watching the compost thermometer closely for the next few days.
Composting dos and don’ts:
- Monitor the temperature closely. Your pile temperature should go to 131 F/55 C for a full 3 days. When it has done so, it’s time to turn the pile. Then let it get hot again, and again turn the pile. Don’t let the temperature get higher than 155-160 F, or your beneficial organisms will be killed.
- Make the pile at least 1 meter tall and 1,5 meters wide.
- Bury your kitchen waste deep, otherwise you’ll have critter problems.
- Aeration of the compost pile is critical! Make sure your composting container has some airflow. You don’t want your pile to go anaerobic!
- Water the pile as you build it, and as you turn it. The moisture content should be such that the compost feels like a dry sponge.
- Don’t let your compost pile get saturated with water. If it’s going to rain, cover it with a tarp, a sheet of cardboard, or something like that.
- If your compost smells bad, it is bad. Do a troubleshoot.
- The color of good compost should be deep, rich brown – not black!
- Use manure from animals raised organically, otherwise it may contain pathogens.
- The compost is ready when it reaches ambient temperature that no longer goes up when you turn the pile.