- The Washington Times - Tuesday, November 7, 2006

In a cool October day, steam rises from a bin as Northwest resident John Wheeler dumps in a pitchfork laden with compost.

The District of Columbia Master Gardener is turning his compost pile by moving it from one bin to another. The steam is from the heat created by bacteria that are breaking down the components of the compost into humus, a dark, earthy organic material he will use on his flower, vegetable and spice gardens.

“My idea of composting is to use whatever you have,” Mr. Wheeler says.

After turning the compost, Mr. Wheeler adds a 10-pound bag of coffee grounds from a Starbucks up the road and a ceramic pot full of kitchen waste, mainly fruit and vegetable peels. The coffee grounds provide nitrogen in a pile that already has leaves, which are full of carbon, he says.

Nitrogen and carbon are essential to a fresh-smelling, quick-acting compost pile. Anything organic, however, whether it is a pile of leaves or leftover grass clippings, will end up as compost.

“There’s an expression called ‘compost happens.’ Whether or not you want it to happen, it happens,” Mr. Wheeler says.

Cold composting is a matter of throwing the material to be composted into a pile and leaving it alone, but the process can take a year, Mr. Wheeler says. Alternatively, a hot compost pile is turned regularly and can finish in six weeks, he says.

Composting occurs when billions of microorganisms, mainly bacteria, fungi and protozoa, digest yard and kitchen waste into humus, joined by earthworms and insects when the pile cools.

Compost can be left in a pile or placed in bins that are prefabricated or home-built out of pallets or 2-by-4s and plywood. The bins keep away yard critters and hide the decomposing process from view.

“The nice thing about [bins] is that they’re attractive, so it doesn’t look like you have a messy pile out there,” says Charles Nardozzi, horticulturalist for the National Gardening Association in South Burlington, Vt.

The bins vary in structure and can be solid, open in front or stackable so the compost can be moved section by section from one stack to another. Motor-operated drums are another option to stir up the compost.

“The point of turning a pile is you expose all parts of it to air to make it go faster. If you don’t turn it, air doesn’t get to the middle of the pile,” says John Bouwkamp, associate professor of plant science at the University of Maryland at College Park. He holds a doctorate in horticulture.

Turning a compost pile one to two times a week is recommended to speed up the decomposition process, says Steve Dubik, horticulture consultant for the Montgomery County Extension Office in Derwood and professor of landscape technology at Montgomery College in Germantown. So does chipping up or grinding the materials going into the pile to create smaller surfaces that can decompose faster, he says.

The compost pile should have a mixture of green and brown materials, according to metropolitan-area horticulturalists and gardeners.

Green materials, such as grass clippings, weeds and fruit and vegetable scraps, have chlorophyll in them and are high in nitrogen. The browns are dry and dead plant materials that consist of carbon, such as autumn leaves, wood chips and shredded office paper.

The green and brown materials can be layered and watered every couple of inches because moisture is needed to help heat the pile, Mr. Nardozzi says.

Microorganisms use the carbon layer as their source of energy and the nitrogen layer as their protein, says Mr. Bouwkamp, vice president of the Mid-Atlantic Composting Association, an association of composters and researchers from the District, Maryland, Virginia, West Virginia and Delaware.

“You need energy, protein, water and air. That’s what you need to stay alive. That’s what the compost pile needs to stay alive,” Mr. Bouwkamp says.

The right combination of green and brown materials allows the compost pile to heat up to 140 degrees, a temperature high enough to kill the pathogens, diseases, insects and weed seeds that might be in the pile, Mr. Nardozzi says.

“The carbon is like the fuel for the pile. That’s the thing the microorganisms eat. The green material is the thing that gets things going and jump-starts the microorganisms,” he says. “Nitrogen ignites the pile, and carbon is the fuel that keeps it going.”

A nitrogen-carbon ratio that is out of balance can cause odor problems, Mr. Wheeler says. A compost pile too rich in nitrogen, such as from a pile of grass clippings, produces ammonia, and a pile too rich in carbon becomes anaerobic and smells like sulfur dioxide or rotten eggs, he says.

“Either one of these can be prevented by turning the compost pile regularly, preventing the compost pile from getting too wet and maintaining the proper carbon-nitrogen ratio,” Mr. Wheeler says.

Mr. Wheeler also recommends avoiding using cooked vegetables and anything with fats or oils to prevent attracting rodents and other pests to the pile. He suggests keeping the compost pile to a cubic yard, a size large enough to produce enough heat to cause compost to act quickly, but not too large to prevent oxygen from getting to it.

Once finished, the compost should be a dark brown color, moist but not wet, and have a nice earthy smell, Mr. Nardozzi says.

This humus can be used to make “compost tea” by putting it in a fine mesh bag, burlap sack or cheesecloth, soaking it in water, then pouring the mixture onto plants.

“That’s a nice way to add compost to plants quickly to give them a little jump-start or boot,” Mr. Nardozzi says.

Humus also is used to improve soil quality and to add and provide slow release of nutrients, such as nitrogen, potassium and phosphorus. Humus loosens up, aerates and makes heavy clay soil more permeable to water and improves the ability of sandy soil to hold water.

“Everything the plant needs is in that compost because it once was a living plant,” says Tyler Diehl, head of gardens at Ladew Topiary Gardens in Monkton, Md. “You can consider compost as an organic fertilizer.”

Composting also reduces the amount of materials that wind up in a landfill, Mr. Bouwkamp says.

“It’s being nice to the world when you make your own compost,” he says.

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