Feedback on Night Soil: Composting Human Waste

One reader writes in to answer a question about composting human waste into fertilizer, and a second reader offers recommendations for venting an outhouse.

| September/October 1973

Night Soil - Privy - Fotolia

Composting human waste — aka "Night Soil" — can be easily done in a way that also controls any problems with flies or odor. 


In MOTHER EARTH NEWS Edith Little asked for information about using yeast in a privy to decompose and deodorize feces or "night soil." I don't know of any yeast that will serve this purpose, but I do know that composting human waste can be done very nicely. There will be little objectionable odor ... much less than from the average privy where waste is allowed to pile up and putrefy, creating unhealthy conditions. Flies will also be eliminated and the resulting fertilizer will be of very high quality: an odorless, crumbly black gold for the garden.

In order to compost effectively and efficiently, night soil must be mixed with material that is high in cellulose or carbon. I find that sawdust, wood chips, pine needles or old leaves—in a ratio of four or five parts sawdust or whatever to one part excrement by volume—seem to work best. Straw or hay isn't satisfactory, for it tends to pack down and is difficult to turn over later on.

The sawdust should be dumped down the hole of the privy after each use to completely cover your latest "gift to the earth". Use more if necessary, to insure that flies cannot get down into the night soil to lay their eggs. The mixture should be kept damp but not sopping wet.

After a period of time, as the pile builds up in volume, it will begin to heat. At this point the material should be turned over with a long-handled pitchfork every two or three days, depending on how much the privy is used. This will keep the pile cookin' by supplying air to the aerobic bacteria responsible for the composting process ... and will also insure that any stray fly larvae on the surface of the mass get dug into the hot center and destroyed.

The heat is caused by the work of beneficial microorganisms which break down the night soil-sawdust mixture. If conditions are right, the temperature will be high enough (at least 150° F for about 24 hours) to render the compost completely free of any disease-causing bacteria. As an added safeguard, I would not use the fertilizer on plants that will be eaten raw until the dressing has aged for at least one year.

It would be advantageous if the privy were designed to allow easy access to the composting chamber for turning and removal of the contents. The facility could be as simple as a tarp strung over a three-foot-deep pit in the ground ... all that's needed is something to keep the pile from getting too wet.

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