Compost Happens!

For my birthday this year I taught a workshop on composting. Well, almost. It was actually my birthday (although no one but me knew it) and I was asked to give a workshop on composting but warned (because it's the summer) no one might show up. As it turned out, a few people did show up and we had an informal and meandering discussion on compost (among other things). I did have a handout which I gave out and that's the material below. Most of it has been taken from other handouts I've gotten. (I've also talked some about composting in my post about Waste, 5/25/09.)

Yard waste and food scraps make up almost a third of our household waste. Composting turns them into rich, earthy organic material that improves the soil and nurtures plants. It also stops organic stuff from going into landfills where it gives off methane, which is a lot more potent as a greenhouse gas than carbon dioxide!

There are many different ways of composting, but the most important thing to know, is that it's not hard. Whatever you do, compost will happen. Organic stuff is just going to decay. There are things you can do to make it faster, and less smelly and messy, but it's going to turn into compost whatever you do.

Of course, you don't want your compost to smell bad. To make certain that it isn't going to be smelly or messy, you want to be sure that what you are composting gets plenty of fresh air, and that you mix things with a lot of nitrogen (often called 'greens' or wet stuff) with things that have a lot of carbon (often called 'browns' or dry stuff—however, some brown stuff, like manure, is actually high in nitrogen). Food scraps are high in nitrogen so it's good to mix them with dry leaves, or saw dust, or wood chips, or paper towels, or cardboard, or shredded newspaper. A good mix isn't too wet or dry, and can get some air, doesn't smell bad, and will eventually create 'humus', which is a moist brown material that looks and smells like good soil.

Two main ways of composting are using compost bins and using worm bins.

Compost bins are big outdoor bins that will take lots of materials. If you only put yard waste in it, you don't need much covering but if you add food scraps you need to make sure animals can't get in it. Because you don't want to attract animals, don't put meat, bones, and oily, fatty stuff (cheese, dairy, etc) in urban composts.

Check your compost now and then. It shouldn't smell, it should be moist (like a wrung out sponge), and it should have plenty of life in it. You may see earthworms and all sorts of bugs in your bin (don't be surprised to see pillbugs, sowbugs, springtails, or millipedes scampering around), but there is lots of microscopic life in there as well that's busy breaking things down. All this vibrant life is good! They do the actual work of creating finished compost.

Your compost is done when there aren't many bits of things and it just looks like a rich earthy dirt. If there are still bits of stuff in it (eggshells, sticks, corncobs, avocado skins, etc), you can sift it with a screen and get very fine humus.

Composts can be 'cold' or 'hot'. A cold compost takes a long time (as much as two years), requires little work (just a layer of 'greens' and a layer of 'browns'), and little or no turning. A hot compost can be done in months, maybe even weeks, depending on how much work you are willing to do (constant turning, cutting scraps up before composting, paying a lot of attention to the carbon:nitrogen ratio and the moisture level, etc.) A hot compost can get very hot—you can get temperatures of up to 150 degrees in the center, hot enough to burn your hand.

Big 'industrial' composts run very hot and can breakdown meat and bones, as well as 'compostable' plasticware and chip bags, that will not compost in your backyard compost bin.

Worm bins (also known as vermicomposting) are small, shallow bins that you can keep in your house. The worms in these bins are usually red wigglers, which are different from earthworms. (Don't dump these worms in the soil when you are done—red wigglers are actually an invasive species.) Make sure that the bin has holes (and cover with screen to keep out flies). Fill with shredded newspaper, moisten and fluff. Add worms. Feed them food scraps (vegetable and fruit scraps—no meat or dairy—and they also don't like onions, garlic, peppers, citrus fruits, avocado or eggplant skins, spicy foods, or anything fermented or moldy). These worms like a temperature between 40 and 80 degrees and their 'bedding' should be kept slightly damp. When everything looks like compost, harvest the 'worm castings', put in fresh newspaper strips and food scraps and start over.

You can put your finished compost on top of the soil around your plants and let the nutrients wash down, or you can mix it with regular soil before you plant. Either way your plants will thrive on the rich soil that the compost will create.

Happy composting!


Quote of the Day: "I hesitate to use 'home vermiculture system' exclusively because the term itself might frighten away some who would feel more comfortable with 'worm bin'. It sounds a lot less intimidating to just build a wooden box with holes in the bottom, add moistened bedding and worms, bury garbage, harvest worms, and set up bedding as necessary." - Mary Appelhof