Quick, Efficient Composting
Our correspondent in Santa Fe, New Mexico writes in to tell us of an encouraging sight he sees. One of the city’s schools is flanked by a number of raised garden beds where the students grow vegetables in the spring and summer. Nearby are a half-dozen compost tumblers into which he’s seen students loading the remains of those gardens as well as leaves and kitchen scraps. This extends the students’ lessons that start with simple seeds. Not only are they learning about plants and other aspects of biology, they’re learning about recycling waste, building healthy soil, and the science behind decomposition. Imagine the possibilities.
The main thing this sight brings to our New Mexican friend (he admits) is jealousy. He only has one compost tumbler and he wishes, like the students, he had more.
The benefits of compost tumblers make them perfect for most home gardeners. They keep their contents neat and contained. Not all of us think that a compost heap is a beautiful thing (right, dear?) but even those who see a pile of decomposing leaves and grass clippings as an eyesore can’t slight the sight of an efficient compost tumbler. The best thing about them? They make accomplishing the act of composting much easier. Why spend time with a garden fork turning over a heavy and unruly heap every few months when a few cranks and turns mixes your compost and provides the aeration it needs to work effectively?
And that’s the other great advantage. Compost tumblers, when used correctly, can speed up the process, doing what might take years in a moderately efficient heap a matter of months in a tumbler. Again, this happens only when the right conditions are applied. Though that’s not difficult, its the reason you may have heard your neighbor complain that he didn’t end up with finished compost in nearly the time he thought he would. But again, with a little attention to detail, you can turn a tumbler full of scraps into a wonderful soil amendment in a season or less. Here’s how.
Most important is providing the right ratio of green to brown ingredients. This means balancing nitrogen and carbon ratios in a way that’s sutiable to conditions inside your tumbler. Most compost tumblers recommend that you load your barrel with roughly 75 percent grass clippings or green equivalent and 25 percent other ingredients such as kitchen scrapes. This varies from the traditional brown-green mix in open piles or heaps. Why? Because the mostly closed tumbler system affords less chance for evaporation. The other important thing is to take advantage of your tumbler’s rotating feature. Moisture levels are important. If what’s in your barrel seems to dry, as it might be after loading in a pile of leaves on a sunny autumn day, add some moisture, then tumble to spread it around.
Compost should be turned every several days. Turning compost every five or so days mixes more oxygen into the decomposing materials allowing the process to continue at its most accelerated rate. It also exposes more surface of the composting materials to the microorganisms that accomplish the process (see The Biology of Composting). Too much turning can also inhibit the process by short-circuiting the decomposition process and not allowing heat to build. Checking the contents of your tumbler every few days will give you a feel for how things are going, how many days the materials need to reach maximum heat, and just when that heat starts to decline. That’s the time to turn.
Other small tricks: don’t continually add materials to your tumbler. Once it’s reached near full capacity — you want to leave some space so that there’s plenty of air and room for the materials to mix when turned — wait until what’s inside is finished before emptying and reloading. The temptation to add more materials increases as the contents inside decomposes and is reduced. Don’t do it. And make sure, as you go along, that any venting your tumbler has is kept clear. Fresh air is critical to the process.
When starting a new load add a shovelful of finished compost to introduce the microorganisms that will do the work of decomposition. Even better, use one of the compost starter products that concentrate such microorganisms. Such products can speed your results and are particularly useful in the (mostly) closed environment of the tumbler. What about holding compost over winter? We frequently start a batch in the fall with leaves, kitchen scraps (potato peelings), and organic goat manure (because grass clippings are hard to come by then) and turn as long as conditions allow. Eventually, frozen weather or snow put an end to this. We’ve never had a problem but imagine very damp contents could expand and damage the container. But again, we’ve never had this problem. In the spring, start turning as soon as you can. Even after over-wintering, in the harsh Montana climate, we’ve been able to turn out ready compost by the Fourth of July.
Like anything else, you’ll get better using a compost tumbler the more you use it. Pay attention to the details and your own special conditions and you’ll reduce the time it takes to produce a finished batch. You can see the value of having two tumblers going so that you can load one as the other finishes. Our friend in New Mexico says he’s already made his wishes known to Santa. Here’s hoping she’s listening.