Although to be honest, the bins are only 90% done. I still need to pick up a bit more lumber- 5/4 x 4 to finish off the side slats, and probably two more pieces of 5/4×6 to rip down into my sliding panels for the fronts of the bins. My friend Thadd came by this weekend to help me finish the project, and he agreed that they may be a bit overbuilt: “Those aren’t compost bins, those are compost bunkers.” While I disagree that they can double as a tornado shelter, they’re pretty stout.
Since I had a pressing need for the bins, they’re already in use. The bale of straw sitting to the left of the composter (bunker?) was purchased for Halloween. After just a few rainstorms, it’s started decomposing beautifully. I took a chunk of the bale and spread it around the bottom of the bin. The straw will take a good while to break down- it’s primarily carbon- so it’ll help provide space for air flow under the kitchen scraps. On top of this, I’ve started dumping our kitchen waste. Once the mud dries out a bit, I need to start transferring in material from the old compost heap. That will get added in layers- partially broken down kitchen and yard waste, finished compost, and a little bit of soured straw for air flow. I’ll also mix in my “compost inoculant,” cheap dog food. Alfalfa meal is a great source of nitrogen to kick start the decomposition process, but it’s expensive to buy it from the garden center. It’s a lot cheaper, however, to buy it when it’s the primary ingredient in dog food.
So what can go into the compost pile? Standard practice says that virtually anything can go in except meat and meat byproducts (bone, connective tissue, animal fat), dairy, and anything excessively fatty, like oils or nut butters. Small quantities of vegetable oils or nut butters are ok, but too much will gum up the pile and make it hard for the compost critters (microbes) to do their job. There are some hardcore composters who successfully handle meat and dairy, but I’m reluctant to go there. My bins are on the property line, so if something goes awry and starts smelling funky or attracting vermin, my neighbors will suffer.
Yard waste is also a great source of compost material. I’ve got a backyard full of leaves that I need to mulch with the mower, and they’ll get added to the mix. You could add them whole, but they tend to mat together and form a layer that takes forever to break down. Weeds are an obvious addition, but you need to be aware that if your pile doesn’t get hot enough, you won’t kill the weed seeds. Grass clippings are a great source of nitrogen, but ideally they should be spread out next to the pile to dry out for a few days, then added. Otherwise, you’ll end up with a slimy, smelly, anaerobic mess.
As for branches and clippings from pruning, they should be chipped up before adding to the pile. Otherwise they’ll take a long time to break down. I’m stockpiling all my brush and clippings, since we’ll need stuff that will burn quickly for the oven. Which- that’s the next project!