Waste not want not: compost for the environmentally challenged.
Hello, all you Greenies out there, it's time for another episode of Make-it-Green Girls Quick and Dirty Tips for an Earth Friendly Life.
Today I'm finally going to answer the question a lot of you listeners have been asking me about a favorite subject of environmentalists: composting. If you've ever wished you never had to buy potting soil again, never had to fertilize your garden, and could reduce the amount of trash your family produces, composting may be just the ticket.
Ok, the first thing you need when you start composting is a place to put it all.
Heaps on the ground work great for starters in the composing world. Heaps are practically free, since all you do is pile the composting materials in a sort of midden heap, cover it, and walk away. Turning the pile every few days helps keep the bacteria who are running the show from suffocating and dying off. Covering the pile with an old carpet or tarp will help keep down the flies and rodents that are attracted to rotting garbage. However, compost is more than just rotting garbage -- it's soil in the making!
Plastic tubs are great for both aerated and fermenting-type composts. The aerated kind need to have lots of holes in the tub's lid so the bacteria and bugs doing the digestion have plenty of air to breathe. You also need to mix up these composts to keep the inside of the mixture from getting air starved and slowing down the decomposition process. Some bins sold specifically for composting are mounted on a tumbler so you can spin the whole thing around.
Sealed plastic bins can also be used to make anaerobic, or fermenting composts that take advantage of bacteria that live without oxygen. These are a little more difficult to manage, so I'll go into that a bit later, but they're especially useful for people who live in apartments without access to outdoor space. They produce a strong liquor of digested compost "tea" that makes a great plant food.
Finally, worm houses are a mix of both heap and tub. In the heaps, you often get beneficial macro-organisms that will move in and lend a hand. However, you can also get unwelcome critters like mice or racoons, and there's no way to get the worms and beetles to stay. As an alternative, you can set up your own vermiculture, or worm farm. You can buy worms online, through the mail, or from local gardening stores and add them to composts not only to eat up the goodies you leave for them, but they leave behind their nutrient rich droppings, called worm castings, which plants love.
Check out the resources at the end of the transcript for more information about where to get compost containers. It can pretty much be any size, as long as you keep the proportions right. Don't forget you have to turn them, so the bigger it is, the more mixing you'll have to do.
OK, now that you have a container, it's time to add your compost mix. There are two categories of materials that are mixed together to create a balance of chemicals in the compost. You must have carbon and nitrogen compounds, oxygen (for the aerated kind) and bacteria to act on these three things.
Most of the time the bacteria are already in your food, waiting for a chance to break it down. Oxygen is in the air already, so as long as the system is aerated (meaning you fluff it every once in a while) things should go great if you balance out the last two things: carbon and nitrogen.
Fibrous, dry, carbonaceous stuff provides the primary carbon source for the compost, keeps it from getting soggy and drowning the bugs and microbes, and provides structure on which molds, fungi, and other beneficial organisms can grow.
Great material for the carbonaceous bits are things like newspaper, cardboard, junk mail sans plastic windows, paper towels, sawdust, and even the crud you clean out of your vaccuum, provided your carpets are not synthetic. If you put too much of this stuff in, your compost will sit there and do nothing, since the microorganisms acting on your compost cannot survive without water.
Wet, nitrogenous, greenish stuff provides a lot of the nitrates needed for the bacteria to act, as well as the moisture medium for them to swim about it. The nitrogenous bits are all those food scraps you can't put down the drain like fruit and veggie peels, roots, and stems; leaf litter and lawn cuttings; coffee grounds and tea leaves; pet and human hair*; and manure from herbivorous animals.
Most of this stuff is pretty wet, and will only get juicier as the bacteria begin to break it down. Make sure you are balancing the dry carbonaceous material with the wetter nitrogenous material. Compost that is too wet will begin to drown the aerobes and begin fermenting, not to mention become very stinky. While fermentation is a useful composting process, it is better to have a separate air-tight container for anaerobic compost.
Putting together composts is a matter of balance. Getting the right proportions of dry and wet material, adjusting the carbon to nitrogen ratios, and making sure the pH and temperature are within optimal ranges. Alternate layers of wet and dry, carbon and nitrogen to build your compost pile, and make sure to add sufficient junk mail with the leftovers.
If it rains a lot where you live, the compost needs to be under the awning or a tarp to keep the rain out -- worm farms extra much (they'll drown). If your compost does get soaked, just add extra dry materials like cardboard and mix it up a few times so it will not become to soggy.
Covering the compost with a layer of dry material will insulate the pile, which speeds composting, and also helps to prevent flies, vermin, and that whole smell problem. Be careful that your compost does not overheat from the energy released by the microorganisms, however; otherwise the whole community will die and your compost pile will stop composting.
On the other hand, if you live where it freezes, you do need to keep the compost from getting too cold. Compost is self-heating, but you do need to keep it insulated in winter.
Most kitchen scraps and vegetable matter tend to be acidic, and high acidity is another killer of good compost. You can adjust the acidity with wood ash from wood-burning fires, stoves, and grills, or you can buy limestone or other alikali materials to add to overly-acidic compost.
Eggshells, seafood shells, and bones are also very good alkali materials to add to a compost pile, but they work best when they are dried and then crushed. If you do not crush them, they will take a very, very long time decomposing.
What Can't I Compost?
There's a short list of things you might think make great compost, but need to handled in a particular way or just thrown in the trash.
Manure from carnivores like cats and dogs contain harmful bacteria and parasites that must be dealt with very carefully, by very experienced composters. Only a "hot compost" will kill parasitic worms that can otherwise harm you and your family. Closed and open systems can reach temperatures high enough to sterilize cat and dog feces, but this must be monitored before you use it on your garden or let your kids anywhere near it. It's generally a good idea to let cat and dog feces to compost for about a year before handling it and using it in your garden.
Fats and oils and meat and fish can be composted, by not in "open" type compost systems. If you have a closed rotating bin, a countertop fermenter, or worm farm, you can compost these things in small amounts. However, go listen to Episode 22, The Carnivore's Dilemma. It will help you cut down on the meat consumption and savor every bite.
Plastic will degrade slower than dictators give up power. Trying to compost plastics is more of an experiment to prove to yourself how slowly it goes, but if you want to try and see, make sure to cut it up into really small bits.
Metals and glass will never bio-degrade. Take them to the recycler instead.
*A note on hair: The reason it goes with the food scraps it that hair is mostly made of proteins linked together. Proteins are high in nitrogen, and thus belong with the nitrogenous "wet" compost bits.
UC Davis student run composting program
Scott, Nicky. Composting: An Easy Household Guide
Hints and products for city composting