Composting Systems

There are a tremendous number of options for containing your compost. Some people choose to go binless, simply building a compost pile in a convenient spot on the ground. Others build bins from materials such as recycled pallets, or two-by-fours and plywood. And, of course, there are many commercial bins on the market.

The question arises, "Which system is best?" Each system has advantages and disadvantages that you should consider when making your choice. However, there aren't many significant differences in actual composting performance between the various traditional bin systems (two exceptions might be worm bins and drum/turning units). More important to the success of your efforts is taking care to provide the proper environmental conditions for composting. Choosing a type of bin is much more a matter of asking questions such as, "How much kitchen and yard material do I have for composting?" and "What system best fits my preferences for neatness, attractiveness, and convenience?" If you're agonizing over choosing a recycled-plastic, dome-shaped detrital digester model for $259 versus building your own setup from $199 of lumber and hardware, you may wish to slow down before laying out all that cash, and make sure that what you end up with will really meet your needs. There are some very attractive and well-engineered commercial bins out there, as well as plans for excellent do-it-yourself models. But why not find out about all the options? Many people, for instance, are very fond of low-cost, attractive units built out of wooden pallets that are free for the asking from local businesses.

One very strong recommendation that I do have is to AVOID THE USE OF TREATED LUMBER when building a bin system. 'Pressure-treated wood' (also known as CCA), which commonly has a green tint, contains arsenic, a highly toxic element (it also contains toxic levels of copper and chromium). There is evidence to suggest that arsenic will leach into your compost if you use CCA lumber in the bin. Unfortunately, many extension services and local governments actually recommend using this stuff for building compost bins. If you are contemplating using CCA wood, please take the time to read the information in the 'Letters' section of Organic Gardening Magazine, April 1994 and July/August 1992, before beginning.

Possible Composting Systems:

One Bin Systems:

A one bin system is the simplest way to make a compost pile, and is a great way to get started. If you plan to make a lot of compost, one bin may not be enough capacity, but adding another can be a simple matter. The basic idea of a one bin system is to make an enclosure for your bin that is at least three feet (or about one meter) across, although you may also choose to use no bin at all if you don't need to keep everything tidy. Possible construction materials include free wooden pallets from local businesses, lumber, cinder blocks, or even steel posts and wire fencing. Once you've made your bin (or decided not to), you might build a pile all at once if you have the ingredients, but it's more likely you'll build the pile over time as you generate compostable materials.

If you build the pile over time, the stuff on the bottom will decompose first, since it will have been there the longest. When there is finished compost at the bottom of the bin, and you want to use it, simply remove the unfinished compost from on top, take out what you need, and throw the unfinished compost back on top. If your pile is not a high-temperature pile, you may want to let redworms (a kind of earthworm) help make the compost. They'll make the process go more quickly, and can create a very high quality finished product.

Two Bin and Three Bin Systems:

These systems consist of two or three adjacent bins, and may be made out of the same materials as a one bin system. The advantage of having more than one bin is that one can have a bin for the pile being built (as ingredients are accumulated over a period of time) and another one (or more) for a pile already built that is in a more advanced stage of decomposition. If you have the space for such a system, and are generating or gathering enough materials to keep the bins in use, this can be very convenient. When you start using a system like this, build your pile in one of the bins. When this bin becomes full, 'turn the pile' by transfering it to the adjacent bin (a garden fork or similar tool will help). This will aerate the pile and hasten decomposition. An alternative that I have found to be very successful is to let redworms do the turning 'in place' (this way I save myself labor and just leave the pile in its original bin). Whatever you choose to do, you can now begin to build a new pile in an empty bin while the first pile continues to decompose.

I find that a two bin system works well for me, but other people generate more compost or like to have a bin for storing finished compost, and therefore choose a three bin system. In a three bin system, you might start by building a pile in the leftmost bin. The original pile is turned into the middle bin when it's time to begin building another pile, aerating it to accelerate the composting process. Another pile is then built in the leftmost bin. When that pile is completed, the old pile (which is now in the middle) is turned a final time into the rightmost bin for finishing, and the just-built pile is turned into the middle bin, making the leftmost bin available for yet another pile. Finished compost will eventually be removed from the rightmost bin. Get the idea?

Rotating or Tumbling Systems:

The cost of these systems can be quite high, and they are somewhat small, but these factors are balanced out by the speed at which drum/tumbler systems can generate finished compost. Under ideal circumstances, compost may be finished in three weeks in a rotating drum composter! Fill the container partly full with a mix of greens and moistened browns, and then give the unit a turn every day or so to aerate the ingredients and remix them. It's important not to pack the container full, because the ingredients won't tumble and mix if packed in tightly.

While one batch is composting, you can accumulate the materials for the next batch. When the first compost is finished, you can dump in the materials you've saved to make more. It's possible to maintain relatively high temperatures in drum/tumbler systems even if they are small, both because the container acts as insulation and because the constant turning keeps the microbes aerated and active.

Sheet or Trench Composting:

This may be the ideal system for people that have garden space who don't want to fuss with bins and piles. Simply bury your kitchen wastes in a trench 8" deep dug in the garden, leave the buried materials to rot for a few months, and then plant above them. By the time you plant, the materials will have rotted into stuff in which plant roots will thrive. If you have copious amounts of materials to get rid of all at once, such as autumn leaves, you might want to spread them around the garden and rototill them into the soil (this is best done in the late autumn, or at least 2 months in advance of planting in the area).

Commercially Available Bin Systems:

Commercially available bins are typically somewhat expensive compared to do-it-yourself bins, but they do keep your compost neatly enclosed and can provide an 'instant solution' to the question of how to set up a composting system. In performance, many of the plastic bins may help to insulate the compost somewhat, allowing decomposition to occur later into the cold season. However, I don't feel that there are major advantages in the actual composting performance of commercial bins -- they function more or less the same as a one bin system (described above). A few brands seem to claim that they are able to harvest some kind of special cosmic energy or the power of the pyramids in assisting decomposition. Nonsense. They certainly can function just fine as compost bins, but there is no magic involved.

Many of the companies selling plastic bins manufacture them from recycled plastic. If you plan to get a pre-built plastic bin, keep your eyes open for ones made from reclaimed plastic -- support recycling and businesses that sell recycled products!

Clean Air Gardening - http://cleanairgardening.com - Compost bins, manual reel mowers and other environmentally friendly lawn and garden tools. Free US ground shipping!

Worm Bin Composting:

Maintaining an enclosed bin specifically for 'vermicomposting' is an excellent way to take care of food wastes. In fact, such a system can even be kept indoors. With the exception of holes for drainage and ventilation, worm bins for indoor use are typically completely enclosed, with a lid of some sort to cover the top. Outdoors, worms can be turned loose in a pile in your compost bin, or contained in a worm bin built specifically for vermicomposting.

Some municipalities, fearful of rodent pests and the diseases they may carry, discourage or even prohibit the composting of food wastes in open piles, recommending enclosed worm bins instead. A sturdy outdoor worm bin is protected from pests, and produces compost quickly during the warm season (or year-round in mild climates).

One of the challenges of beginning a vermicompost system is finding a source of worms. A typical earthworm from the garden won't do. Vermicomposting requires a species that is adapted to living in decomposing organic materials rather than in the soil. Two species are Eisenia foetida and Lumbricus rubellus. Also known as the redworm, manure worm, or red wiggler, Eisenia foetida is often available at bait shops (ask for red wigglers), but can be mail ordered less expensively from worm farms listed in the classified ads of Organic Gardening Magazine. Governments and organizations that promote vermicomposting may maintain 'worm banks' as a low-cost source of worms for the general public. Seattle Tilth, in cooperation with Puget Consumers Co-op, has a worm bank at a composting demonstration site in back of a PCC grocery store.

The general idea is to provide a cool, moist bedding (some kind of 'brown' compost ingredient such as shredded leaves or paperboard) for the worms to live in, and then bury kitchen wastes in the bedding. As bacteria and fungi begin to decompose the materials, the worms graze on the bacteria and fungi, and also break up the ingredients with their movement through the bedding. Eventually, the worms have ingested the ingredients and bedding, turning it all into worm castings (feces) that are an excellent finished compost.

Composting with worms is very easy to do, but there are a few basics of vermicomposting that are helpful to understand. I plan to provide a how-to guide some day. Meanwhile, you may wish to read the vermicomposting guide available on the World Wide Web from CITY FARMER, an organization in British Columbia.

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