Compost Bins - October 27, 2004
Jeff Schalau, County Director, Agent, Agriculture & Natural Resources
Arizona Cooperative Extension, Yavapai County
As Iíve said before, you are not a real gardener unless you make compost. Aside from reducing the amount of waste entering the regional landfill, you will have a useful product that benefits your garden. There is a lot to know about successful composting and plenty of information is available in books and on the Internet. While the concepts behind making compost are constant, some adjustments in methods and compost bin construction will help you make better compost in the arid southwest.
Many compost bin designs were developed for areas having higher rainfall, moderate temperatures, and/or higher levels of humidity. Under these conditions, the compost must have a greater exposure to air to prevent it from becoming too wet and going anaerobic (stinky and nasty). These bins often have wire mesh or large air spaces in their sidewalls. These openings on the sidewalls promote aerobic conditions necessary for healthy compost. While these compost bin designs will function in the arid southwest, they will also require greater inputs of water to maintain proper moisture for the compost-producing microorganisms.
While compost does require adequate aeration, we can conserve some water by using solid sidewalls on our compost bins. Larger diameter compost piles can also help conserve water by minimizing the surface area to volume ratio. Iíve found that solid sidewalls of wood, concrete blocks, or sheet metal prevent water loss and provide adequate aeration. Solid sides help slow water loss and retain heat. If additional aeration is needed, then you can add more coarse materials or perforated drainage pipe.
There are several types of manufactured compost bins. The drum type composters are great for small amounts of kitchen and yard waste. These are rotated whenever new materials are added and are easy to manage. Another type of composter is the upright bin, usually made of UV resistant plastic. These are convenient for depositing compostable waste, but are not easy to inspect and make only small quantities of compost. A third class of composters are wooden slat or wire cage bins. These are convenient and hold larger quantities of materials, but lose heat and moisture more readily.
Many medium-scale compost makers like to have multiple compost bins and there are several designs available on the Internet. Bins provide flexibility to have compost at various stages of decomposition or segregation of materials and/or composting methods. I have a very low-tech two bin setup. The sidewalls are made of corrugated sheet metal attached to metal T-posts with a common wall in between the two bins. For accessibility to the bins, another piece of sheet metal acts as a gate which slides out and is held in place by posts driven into the ground. Each bin is about 5 feet long and 5 feet wide and 2 feet deep. If necessary, I could build it taller. In one of the bins, I usually have some finished compost. When that gets used up, I transfer the materials from the other side, turning it in the process, and add fresh materials to the empty bin.
If you are unsure of which system you should use, then try to envision the amount of waste your household generates over the course of a year. The average household with a small yard, low maintenance landscape, and kitchen waste can probably get by with a plastic bin or drum composter. If you have chickens, rabbits, and a large garden or landscape, I recommend at least two bins. With horses and acreage, you will definitely need large bins or possibly even free-standing piles you turn with a tractor. Regardless of methods/bin configuration, you will probably end up with about ľ of the original volume. Remember: you can never have too much compost!
The University of Arizona Cooperative Extension has publications and information on gardening and composting. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at email@example.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.
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