Audubon: Audubon at Home

Composting can transform your food scraps and fall leaves into an all-natural fertilizer that will make
your garden grow like mad—and your neighbors
green with envy.

Composting changed my life. Seriously. Back in the last century, I was just tapping my way out of a cocoon of environmental ignorance, recycling a few things and potting up a few paltry pansies on my balcony. Working as an advertising copywriter, I was making oodles of money but feeling increasingly unfulfilled selling hamburgers and beer.

One day I happened upon a demonstration garden run by City Farmer, a nonprofit group in Vancouver, British Columbia, that promotes organic food gardening and backyard composting. The little plot of land, bursting with color and wild with scent, drew me like a fruit fly to an overripe peach. I started volunteering immediately. My first job? Separating worms from their castings. It turns out that getting a little dirt under my well-manicured nails was just the thing I needed.

There, in the "worm corner," I sifted crumbly black compost through my fingers. After months of decomposition, old vegetable peels and autumn leaves had been reborn as black gold. Soon it would coax squash and peppers, peas and primroses, from the ground.

I was witnessing a renewal, and experiencing one, as well. It wasn't long before I traded in my three-piece suit and heels for coveralls and clogs. The metamorphosis was complete: I took a 50 percent pay cut and became City Farmer's Compost Hotline operator.

For the past 13 years I've been fielding 4,000 calls annually. Each year our group spreads the compost gospel to an equal number of garden visitors, too. And why not? Composting is an awe-inspiring cycle: It takes food scraps and yard clippings—otherwise destined for a landfill and indefinite preservation—and returns them to the earth as a first-rate fertilizer. And most of the work is done by millions of creatures so small you can't even see them toiling away.

A healthy compost pile is teeming with life. It holds an entire food web, starting with thousands of different species of bacteria that break down organic matter, creating heat. They're soon helped out by other decomposers, like protozoa and fungi, and then larger organisms begin to arrive. Nematodes, millipedes, mites, earthworms, and other invertebrates eat the bacteria and also one another, and their waste products further enrich the compost.

If you've provided the right balance of carbon, nitrogen, water, and oxygen for these organisms to thrive, the finished product will consist mainly of humus—a dark, spongy substance with a good physical structure that resists erosion and allows water and air to move readily through it. Soil with a lot of compost not only drains well, which helps prevent plant roots from drowning during heavy rains, it also holds water in times of drought. A good flow of oxygen will stimulate the growth of more beneficial organisms.

Compost is able to store and gradually release nutrients like nitrogen, phosphorus, and potassium for plants to use as they need them. (By contrast, chemical fertilizers may simply wash away or provide a short burst of more nutrients than plants actually require at the time.) The microbes and fungi in compost release nutrients locked in your garden's soil, too. The strong, healthy plants that result are able to resist pests and disease, rendering costly and polluting herbicides and fungicides unnecessary.

COMPOST, IN AN EGGSHELL Here's the step-by-step. 1: Layer three to four inches of woody, brushy material in a rodent-resistant bin. 2: Alternate two- to four-inch layers of green, nitrogen-rich material, like vegetable peels and grass, and brown, carbon-rich material, like fall leaves and newspaper. 3: Whenever you add a layer of food scraps, sprinkle it with soil and cap it with a brown layer to prevent odors. 4: Mix the bin's contents at least once every two weeks. 5: If the compost is very dry, add enough water to make it about as moist as a wrung-out dishcloth. 6: Continue to add and mix layers until the bin is almost full. 7: After two or three months the compost will resemble dark, crumbly soil. It's ready to use!

Over the years city Farmer has run thousands of composting workshops at the garden, so we've boiled our technique down to a basic recipe. It all starts with a bin. Open piles (here in the city we call them "rat hotels") are simply oozing with the potential to create un-neighborly confrontations, so it is generally best to use a container.

Select a bin that is easy to work in; it should have a wide mouth, a locking lid, and a trapdoor at the bottom for shoveling out finished compost. A single bin is fine, or you can set up two or three to have compost at varying stages of decay. Plastic bins are the least rodent-resistant; wood and wire bins are much more so. Make sure wood bins are lined on the sides, the bottom, and the underside of the lid with 16- or 20-gauge wire mesh. Quarter-inch mesh will keep mice out; half-inch will keep rats out. If you're going to use plastic bins, it's also a good idea to set them on a sheet of mesh to keep rodents from burrowing up from underneath.

Now that you've got your container, place a two- to four-inch layer of straw or twiggy material on the bottom to allow air to circulate upward. Then alternate two- to four-inch layers of green and brown materials. Your green (nitrogen) materials are primarily food scraps, garden trimmings, and grass. Your brown (carbon) materials should be dry fall leaves, straw, or even stripped-up newspaper. Whenever you add a layer of food scraps, sprinkle it lightly with soil to suppress smells and smother fly eggs. Plus, soil is a natural accelerator and will help kick-start your compost with helpful bacteria. Then cap it all off with a brown layer. Mix everything up every couple of weeks with a pitchfork or a compost aerator you can buy at gardening stores. (A ski pole will work in a pinch.) This introduces oxygen into the bin and gets the microbes munching again.

In two to three months you should have a dark, rich fertilizer, slightly moist and practically odorless. It should clump together if you squeeze it but fall apart when it drops; if anything, the compost should smell a bit sweet and earthy. Notice I say should.

"We call our compost pile 'the fruit bar,' " says Wynema Lovell of the Duval Audubon Society in Jacksonville, Florida. "The rinds of all the fruit we eat—watermelon, cantaloupe, pineapple, and apples, whatever's in season—go into the pile. Now a raccoon has discovered the fruit bar, too!"

The Lovells don't mind their visitor ("We think it's kind of fun!"), but the most common complaint on the compost hotline is from people whose bins have become a social hot spot for animals or flies. Often these callers have forgotten to properly bury their food waste with a layer of soil. Animals can be pretty ingenious when sufficiently motivated, so it pays to outwit them. If you have varmints like raccoons, you might want to secure the lid with a bungee cord. If you live in bear country, sprinkle fruit with lime before burying it well beneath leaves.

To further avoid odors, stick to uncooked fruit and vegetable waste, coffee grounds, tea bags, and eggshells only. That means no cooked food, no meat, no fish or bones, no dairy products, no fats, and no oils. In a backyard bin, I also recommend avoiding grains, including bread products, because they really reek during decomposition. You then run the risk of attracting rodents or offending your neighbors.

Your compost needs to warm up to between 110 and 140 degrees Fahrenheit, hot enough to kill weed seeds and pathogens but not so hot that it will fry the good bacteria. Special compost thermometers can measure the temperature on the inside of your bin. A lower-tech clue is that the compost's surface should appear almost steamy; if you hold your hand above it, you should be able to feel the heat. If your compost isn't hot enough, try adding grass (wait three cuttings if you've applied any sort of chemical fertilizer or herbicide) or, if you live in a rural area, horse manure.

Layering on too much green, however, throws off the balance, slowing down decomposition. There is just no excuse for that, as many compost fanatics will attest. Most communities are so filled with browns that they've inspired a whole new crime category: the leaf thief. Patricia and Ronald Schauer from the Willapa Hills Audubon Society in Longview, Washington, often skulk around town on the prowl for compost fodder. "We collect leaves from the neighborhood in the fall," Ron says, though "only after the neighbors rake and bag them!" They've also been known to walk off from church suppers with leftovers like lettuce to add to their two large bins. Patricia is a retired kindergarten teacher; she and her husband periodically collect coffee grounds from school staff rooms, too. "Caffeinated worms seem to work faster," Ron adds.

If you live in a hot, dry climate, your bin will dry out more quickly, so you'll need to dampen it regularly. The moisture content you're looking for is like that of a wrung-out dishcloth. Since open wire bins or compost cages expose the contents to the elements, they tend to be too dry or too wet. In climates like the Pacific Northwest, where the air is always moist, you'll almost never have to add water. The food scraps and grass clippings provide all the moisture you'll need.

In mild climates you can compost nearly year-round. In frigid regions the compost will freeze up in winter. That's when dedicated composters turn to worm containers indoors.

A "vermicomposting" container is much smaller than a backyard bin and can be kept inside or on a balcony, making it an ideal choice for apartment dwellers, too. You don't invite just any old worm into your house, though—red wigglers are the guest of choice. They can eat their weight in organic matter every day, aerating the pile themselves, and their excretions are rich in nutrients. Worms are also a great way to turn kids on to composting. When shes not out stealing leaves, Patricia Schauer sets up classroom bins where students can compost some of their lunch leftovers.

Composting can involve a lot of trial and error, but when you've achieved the perfect product—dark and moist and rich—it's time to let it unleash its power. Simply lay it over the soil as mulch or dig it into beds or containers. Your onetime vegetable peels and coffee grounds will now propel your garden toward neighborhood fame. "I use my finished compost on the butterfly and tea gardens at my bed-and-breakfast," says Victoria Freeman, also of Duval Audubon. Her guests are routinely intrigued. "When they see the butterflies, beautiful flowers, and all the songbirds at the feeders, they want to know my secret," she says. "I tell them, 'I compost my garbage.' "

This is probably the last answer they're expecting. But once served up an omelet filled with fresh herbs, cherry tomatoes, and green peppers plucked from the organic garden that very morning, her guests are converted, all right. It seems I'm not the only one to make a brilliant career out of composting.