Home & Garden

Jolly Green Goddess readers might remember a letter to the Sun from Christine Condon explaining composting at Sonoma Compost Company where the contents of Sonoma Valley yard-waste cans goes for the conversion process.
A great way to start our new gardening year is to resolve to compost and conserve our earth more consciously by re-using our natural resources instead of throwing them away.
As promised, I contacted Sonoma Compost directly, and soil scientist Will Bakx responded kindly and in detail. Bakx’s clear message is below, slightly edited by JGG with his permission. The main question was whether composting kills bad diseases on plants during the composting process. Apparently if proper temperatures are maintained, as he says they are at Sonoma Compost, it does. (www.sonomacompost.com.)
Sonoma Compost makes that happen with scientific methods, which most of us at home probably can’t do, but we can still do our part and use the compost material to grow our own vegetables and help our gardens naturally.
Bakx stated: “Compost heats up naturally when specific minimum requirements are met. The heating is caused by microbial activity. Since composting is a biological process, conditions for life must be present. 
“But first, you need a pile that is at least three feet by three feet by three feet in dimension. At Sonoma Compost the piles at the beginning of the compost process measure 18 feet wide by 7 feet high and anywhere from 150 feet to 650 feet long. This is necessary to have enough bulk for the heat to build up.
“Next you need the right particle size. Usually a mixture that contains material; material up to three inches works. If the particles are too coarse, the heat escapes too easily. Particles that are too fine exclude oxygen. 
“That leads us to the biological requirements. Living organisms need oxygen to proliferate. (Anaerobic composting, without oxygen, is possible and produces methane for energy, but is not as common. Perhaps a way for the near future though.) 
“The microorganisms also need water, 40-60 percent moisture content, and food. One
teaspoon of compost contains millions of fungi and bacteria. They consume a tremendous amount of oxygen. 
“A porous pile will allow new air to penetrate the pile. As the pile heats the hot air rises and this further enhances the fresh air to be drawn into the pile. Without this natural air movement the microorganisms could run out of oxygen in about 20 minutes. The most common limiting factor in composting is the lack of water. 
“When a handful of material is squeezed the compostable materials must feel wet, however no water should run from the hand. When you open the hand a glistening ball should lay in your palm. If no ball forms, the material is too dry.
“Lastly, the right food must be present. We speak of greens (nitrogen) and browns (carbon). Greens are lawn clippings, fresh leaves and weeds, most manures and food discards. Browns are dried leaves and weeds, straw, woody materials. Approximately four parts of browns to one part of greens works well. Sonoma County has a natural blend of yard trimmings that lends itself beautifully to composting.
“The compost needs to be turned since the outside four-to-six inches do not heat up unless the compost is insulated with a mulch. When turning the pile one must make sure that the pile is inverted. What was in the inside goes on the outside, and what was on the outside goes in the inside of the turned pile.
“Several turnings (five) are recommended to make sure everything has been exposed to a temperature over 131°F (55°C). (Special compost thermometers are available to monitor the compost.) At this temperature virtually all diseases and seeds are destroyed.
“At Sonoma Compost we compost at 131°F-150°F for at least five weeks, during which time the piles are turned five times. Further turnings result in a finished compost in 12-14 weeks.
“Once a disease is killed and the weed seeds are destroyed, they do not regenerate. However, care must be taken that fresh material is not introduced to material in the process of composting nor to the finished compost.”