How Compost Turns Yard Waste Into Black Gold

In nature, there is no such thing as waste. Fallen leaves, twigs, and bits of plant material fall to the ground, where they are broken down by microorganisms, and their nutrients recycled back into the soil to feed another generation of plants. You can mimic this elegant cycle by using your yard waste as mulch, or by turning it into compost. You’ll be keeping a valuable resource out of the landfill, where it can generate the greenhouse gas methane, and the finished compost will save you money and give you healthier plants.

Plants absorb the natural nitrogen in compost more easily than the synthetic nitrogen in fertilizers. Compost also helps soil retain water, saving you money on your water bill. Best of all, you won’t have to spend a cent unless you want to. That’s what I call a real win-win!

Yard Waste gets Compost Happens

To successfully do its job, the “microherd” of fungi and bacteria that digest plant waste needs air, water, a balanced diet, and comfy temps. Getting the right amount of air is easy: Just keep your compost makings loosely packed. The water balance may be harder to maintain. The pile should be moist but not wet—like a rung-out sponge. You may have to add water, or cover things up to keep the rain out. If you don’t always get it right, don’t worry, the microherd will forgive you and get right back to work once you add water or dry materials to balance things out.

Your microherd likes to chow down on a combination of ¾ dry brown stuff and ¼ moist green stuff from your yard waste. The exact amounts aren’t critical, and you don’t have to add a combination every time, as long as the balance comes out about right over the weeks.

“Brown” stuff includes dry leaves, dead weeds and plants, straw, hay, wood chips, sawdust, coffee grounds and filters, torn-up or shredded cardboard, newspaper, or other nonglossy paper, paper towels, napkins, non-wax-coated paper plates, and the like.

“Green” stuff includes fresh plant materials, leaves, fresh grass clippings, and kitchen scraps/leftovers. Avoid meat, fat, or vegetable oils. Traces are OK, but too much won’t break down, is likely to smell, and will attract undesirable scavengers.

Roughly flatten the top of your pile each time you add mixings, so the next additions will have somewhere to sit, and add a bit of water if the stuff is dry. Chop up larger pieces and tuck any moist scraps that might attract insects or critters down a few inches. Alternate thin (no more than an inch or two) layers of “browns” and “greens,” or mix them as you add them. Once the microherd gets going, it generates heat, which means the process is working.

The center of an active pile from all organic yard waste will be hot to the touch, and you should see steam rising on cool mornings. At cooler temps, activity slows, and freezing temperatures will stop the process completely. But you can keep it going through the winter by putting your pile in a sheltered location, insulating the sides, or by covering it with a black tarp.

Where to Keep the compost from yard waste

You can just pile yard waste in an out-of-the way place that’s roughly three feet across (just avoid putting it right up against something you don’t want to rot, such as your house or other wooden structures). You can also contain your compost in a circular pen made from wire fencing, which keeps the walls of the heap open to allow air in and out. Folks with smaller yards and less yard waste to compost can make their own compost bin out of a 55-gallon drum or a large plastic garbage can by drilling ½- to ¾-inch holes every few inches all over it. The microherd should do its job on a pile in roughly six months, but that can vary depending on a wide variety of factors.

It is simplest in the long run to have at least two piles or bins. Once one is full, leave it alone and put fresh stuff in the other. With any luck, the first compost will be done by the time you need the area or container for fresh makings. Your compost is done when few, if any, of the original ingredients are identifiable, and you have mostly crumbly soil that smells faintly woodsy.

Troubleshooting: My compost is smelly. 

Compost should smell faintly woodsy; if it smells bad, something is out of balance. Maybe you added too much green stuff and not enough brown stuff, or there is too much water. Mix in more brown (torn-up newspaper or dry leaves), and cover the top of the pile loosely to keep more rain from getting in while allowing air movement to take excess water away. In the future prepare the yard waste, by letting green stuff dry out a bit before adding it to the heap, and spread it out in a thin layer when you do.

Nothing is happening

You may have too much “brown” stuff in proportion to “green” stuff, and/or too little moisture. Add water if the makings are dry, and cover the pile tightly to keep moisture in. Turning the compost pile helps speed up the process (and it helps dry the pile out, which helps if it’s smelly). It’s not necessary, but if you’re in a hurry, turn it once a week, using a garden fork or pitchfork to pull it apart. Try to keep the least decomposed yard waste in the center, if you can.

Stuff NOT to put in your compost pile:

  • Big sticks or hunks of wood (too slow to break down)
  • Meat, fat, or vegetable oils
  • “Compostable” or biobased plastics (they probably won’t break down in a backyard pile)
  • Cat, dog, or human poop
  • Grass clippings from lawns treated with herbicides (a few chemicals may still be active in the finished compost) or pressure-treated wood
  • Weeds that have gone to seed, or roots from weeds that spread underground

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