Extreme Recycling

Who first thought of dung as food? Was it the dung beetle, or the pig? I suppose if insects evolved before mammals, the palm goes to the beetle. As everyone knows, dung beetles work in pairs to make a ball from the nearest dung pile, where they roll it into their burrow, lay their eggs in it, and leave it as a tasty food supply for their progeny. Pigs will eat the excrement of any species, but rabbits practice a special type of coprophagia; they eat their own soft fresh cecal pellets for redigestion, since they lack the four-chambered stomach of bovines, which recycle its contents to the mouth more discreetly.

Of course, ever since the first farmers noticed that the grass grew greener around a pile of animal droppings, dung has been used for fertilizing crops. In England in times of yore, before chemicals took over, farmers were likely to sniff the air appreciatively after anointing their fields, and murmur "seasonable muck-spreading."

In the United States, cost increases for commercial fertilizer have many farmers looking for manure - which was given away in the past - as a substitute. The manure must be sampled for nutrient levels, and if University of Nebraska soil scientist Charles Wortmann has his way, fed into a "manure value calculator," a spreadsheet that calculates the value of manure for a specific field, including the value of nutrients and their availability, and expected increases in crop yields.

In India, I've seen women squatting in the fields making cow dung into flat round patties, which they then mark with a hand-print, for sale as cooking fuel. I also saw little roadside huts filled with dried cowpats, constructed of cow dung and tastefully decorated with rural motifs worked in the same material.

Cow dung mixed with mud has been used for centuries for constructing adobe dwellings, because it binds to wattle better than mud alone. The mixture also has an ancient cosmetic use. The Nuer people are a nomadic cattle-owning tribe that lives in the Southern Sudan. Their skin is so black it is almost midnight blue in color, and the men go about naked except for fabulous head-dresses made by mixing mud and cow dung in their hair. The long-departed British colonial administration took most unfair advantage of this cultural quirk. Finding it impossible to prevent jail-breaks by Nuer imprisoned for cattle-rustling (they would simply remove their prison garb and climb over the fence), the dastardly prison authorities would shave the prisoner's head, leaving him too ashamed to venture out until it had grown back enough to form the base for a traditional hairdo.

Several medicinal uses for dung have been recorded. Baby elephants are born without the gut bacteria needed to properly digest the plants they feed on. They obtain them by eating the feces of their mothers. Hamsters eat their own droppings, possibly to recover excreted vitamins B and K, produced by their gut bacteria. Apes have been observed eating horse droppings for the salt content. According to Ralph Lewin, writing in 2001 in Perspectives in Biology and Medicine: "Consumption of fresh, warm camel feces has been recommended by Bedouins as a remedy for bacterial dysentery; its efficacy (probably attributable to the antibiotic subtilisin from Bacillus subtilis) was confirmed by German soldiers in Africa during World War II."

Consider also some contemporary dung-based industries. In Indonesia, the droppings of the palm civet (Paradoxurus hermaphroditus) are collected in order to separate out the coffee beans in them. The gourmet viverrids select only the best quality coffee berries to eat, and excrete the beans which, when washed and dried, are turned into the world's most expensive coffee, at $200 for a one-pound gift set.

In Sri Lanka, a company called Maximus collects elephant dung from a nearby elephant orphanage and turns it into paper. This is, of course, environmentally friendly, since the animals provide all the necessary chemicals for processing the vegetable pulp they make. The orphanage receives a portion of the profits. An outreach program called "Peace Paper" pays villagers to collect wild elephant dung for the factory, and is credited with changing the local peoples' view of elephants from crop-destroyers to beneficent creatures. The project was the winner of Shell's World Challenge 2006.

We probably haven't seen the last of imaginative uses for dung.

Jack Woodall is director of the Nucleus for the Investigation of Emerging Infectious Diseases in the Institute of Medical Biochemistry at Brazil's Federal University of Rio de Janeiro.