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The Honolulu Advertiser
Posted on: Saturday, November 7, 2009

HAWAI'I'S GARDENS
Cooking up your own compost easy enough


By Jay Deputy

Most of us homeowners are now getting biweekly green waste pickup. Yard clippings are sent directly to special facilities, where they are processed into usable organic compost that can be put back into your lawn and garden. This puts less pressure on our landfill, used for other types of household waste.

If you are willing to spend a little extra time each month, you can easily make your own compost by saving most of the yard trimmings that you would otherwise leave on the curbside for pickup and using a few other yard care supplies that most of us already have on hand.

The composting process is simply a controlled form of natural decomposition of organic plant matter, carried out by naturally occurring bacteria and fungus. The composting takes place best when the plant matter is confined to a pile or container that is at least as big as a large garbage can.

In order to get started, find a container large enough. An old 50-gallon garbage can with a loose-fitting lid will work great.

Put a few holes in the bottom for drainage and then put in a plastic garbage bag liner. The bag will help you mix all the raw materials when you are ready to start the composting process.

Grass clippings can go directly into the compost can as you mow. Most hedge trimmings containing small woody branches can also be added without further preparation. Coffee grounds and crushed egg shells are also beneficial. Other woody clippings may need to be chopped up before being added to the mix. These can be temporarily stored in the regular curbside green waste can and chopped up later.

Palm fronds and any leafy plant material are OK. A small wood chipper or a good mulching lawn mower with a collection bag can be used. Avoid large, woody branches and clippings from plants that have a milky white sap such as plumeria and oleander.

When you have collected enough material to fill the composting container, pull the bag out of the can and mix everything well. A compost pile needs the right mix of materials to decompose quickly.

Try to have one part green leafy material to two parts chopped woody material.

Mix the parts well as you begin to fill the compost can (do not use the garbage bag this time). Build layers of about 1 foot and sprinkle in a few ounces of ammonium sulfate fertilizer or other lawn fertilizer and a small amount of topsoil or finished compost. Moisten the layers as you continue to build the pile. Water is necessary to start the decomposition. The pile should stay moist but not soaking wet. Too much water will turn the mix sour and give it a swampy odor. When the can is full, cover with the lid and store in a semi-sunny area.

Within a few days, the middle of the pile will begin to get hot. This is a sign that the bacteria and fungal organisms are doing their work. The temperature ideally should stay between 120 and 150 degrees during the active composting. It is not necessary to turn the pile as long as it stays hot, because heat is lost during turning. If the pile stays too wet and becomes stinky, then immediately open up and turn the pile well. If enough water is added in the beginning, it will not need more. Drainage holes in the bottom of the can will prevent excess water from accumulating.

The pile will begin to cool after six to eight weeks. At that point, it is OK to open up and turn the pile. Add water if it feels too dry, cover and continue composting. When the process is complete, the pile will finally cool down and take on the appearance of rich, loose soil. At this point the compost can be moved to another container — large plastic lawn bags work well — and aged for several more weeks before it is finished.

The finished compost should be kept dry during storage. Mix it into garden or potting soil to add valuable mineral nutrients, keep the soil loose and help retain soil moisture.