Next to my trailer I've built a compost bin. At the right you can see what it does. The white straw in the background of the picture at the right is nothing but dry grass clippings raked up after a neighbor mowed a lawn. The brownish stuff in the picture's center is the same dried clipping material after about a week of composting. At the right, the blackish stuff is the same thing after about 3 weeks of composting, but now instead of calling it "dried lawn grass" I call it "high-grade compost"!

Instead of thinking of my compost heap as something like a doghouse or a junk pile, to me it's a neighboring community of right-thinking friends. Here's what I have to say about that community:

• It provides me with the service of changing my left-over vegetable matter (grass clippings, kitchen scraps, rotten tomatoes... ) into something wonderful to add to my garden soil

• I like to think about the chemistry and ecology that keeps the community going

• It's encouraging to see that by understanding how the compost heap works I can give it what it needs, and then it does indeed function exactly as it's supposed to

• When I break open the heap and feel the high temperature inside it, I know that the composting process is going well -- my community is happy

In other words, in this world where so many things don't go right, it's just great living next to a wholesome, hungry, happy, neighbor.

DO YOU REALLY NEED A COMPOST BIN?

If you don't have much stuff to compost, maybe you don't need to build or buy a compost bin. Some folks just toss what little kitchen scraps they have onto their garden soil and eventually the scraps decompose and get worked into the soil. If kitchen scraps have been seasoned with animal products they may attract raccoons or other animals you don't necessarily want in your garden. In that case, you might just collect your vegetable matter until you have a pot full, then go bury it in a shallow hole or trench in your garden. Eventually the matter will become part of the garden soil. You can also compost in a pile lying on the ground without any structure at all. Just feed the pile the right stuff, keep it moist but not wet, and stir it up every week or so to aerate it.

HOW DO YOU  BUILD A COMPOST BIN?

There's nothing magical about the shape or composition of a good compost bin. I'm amazed how people will pay hundreds of dollars for commercially produced ones. My little bins to the left of the pile of hay in the picture were put together in about three hours of work, using boards that were just lying around. The sides are about waist high and the boards were nailed about two inches apart to let air in between them.

I built two bins so that they shared one post and were at right angles to one another. When the bin at the left needs to be aerated, I fork the stuff into the bin at the right, where the "cooking" then continues with new vigor. Most people put their bins side by side, but I didn't have room to do that, plus my way lets more air in when both are filled.

The proof that this is a good system is that it works! When I thrust my hand into the working compost heap it's really hot inside. You can see the big pile of grass clippings next to the bins. Thrusting my hand inside it I find hardly any heat at all because it's not composting -- mainly because it's not moist and I haven't added nitrogen-bearing material to it. More about these matters below...

WHAT CAN BE COMPOSTED?

Mostly people compost vegetables, fruits, leaves and grassblades. Don't add animal products (including bones), wood, plastic, metal, or weeds whose seeds or other reproductive parts such as rhizomes or tubers might survive the composting process. I personally stay away from paper because you never know what chemicals have been added in the form of inks, preservatives, or whatever.

WHAT GOES ON DURING THE COMPOSTING PROCESS?

Mainly, microorganisms break down plant matter into tiny fragments that improve garden soil when added to it. Also, nutrients are made available for your garden plants. There are many kinds of microorganisms that do your composting, and each stage of the composting process requires its own special microorganism community.

When you compost, basically you are managing a series of microorganism communities. This is important to keep in mind because microbes, like humans, are made of a good bit of protein. And protein is made of amino acids, and each molecule of amino acid has at its heart an atom of nitrogen. Therefore, every healthy compost heap must have enough nitrogen for the making of the bodies of the needed  microorganisms. The correct  ratio of nitrogen atoms to carbon atoms (the carbon being in the vegetable matter being composted.) is 25 to 30 atoms of carbon for each one atom of nitrogen.

So, grass clippings, fallen leaves and such provide a lot of carbon but by themselves usually they don't contain enough nitrogen to make really good compost. To convert your grass clippings or leaves to compost, then, you have to add extra nitrogen. Wonderful sources of nitrogen are manure and urine. If you can clean out a livestock stall where the hay has been mingled with manure and saturated with urine, that's great stuff! Mix it in with your grass clippings and you'll get perfect compost. If you don't have such fine stuff, store-bought nitrogen fertilizer bought in a bag will do, though that stuff is made using lots of energy, so you're sort of defeating the idea of doing something earthy. Some people mix bagged dogfood, which has animal parts in it and protein-rich soy meal, into their compost bins to serve as a nitrogen source.

You also need to inoculate your compost with microorganisms. You can buy inoculant at garden shops, or just find some rich soil where organic material has been decaying for a long time, dig up a shovelful, and add it to your heap.

You might enjoy reviewing a page at Mastercomposter.com called "How A Compost Pile Works."

WHAT CAN GO WRONG?

• If you put animals products in your compost heap, raccoons and other critters may dig into it.

• If you let your heap dry out, it will stop composting

GOOD COMPOST is dark brown to almost black. It feels loose and granular, with little or no wood or bark. It should be moist, not soggy or dry. It has a nice earthy-woodsy odor. If your compost has whitish, ashy places in it, it's too dry. If it's blackish and smelling like a sewer, it's too wet. If it has a strong ammonia odor, you're adding too much nitrogen.-

• If your heap gets wet, not just moist, its contents may begin rotting instead of composting, and then you'll have a smelly mess instead of something nice

• If you don't occasionally stir your heap to let air in, particles will stick together and close air channels inside the heap, the microbes won't get the oxygen they need, and composting will screech to a halt

• If your heap has too much nitrogen it may start smelling strongly of ammonia

• If your heap has too little nitrogen, microorganism communities will remain underpopulated and you won't get good composting

Check out composting books at Amazon.com.