As long as the animal kingdom exists, we'll have a steady supply of digestive byproducts, whether you call it dung, manure, sewage, feces, or poop. We may as well use it for something! Oh sure, you know about fertilizer, but there are plenty of other ways we reuse "biological waste."

1. Paper

Poop is composed largely of indigestible fiber, which helps to keep an animal's system clean and running smoothly—as anyone who's dealt with constipation has learned. These fibers are now being made into fine stationery. In Thailand, elephant patties are collected, cleaned, spun, dyed, and dried to make paper that is sold mainly to raise funds for elephant preservation projects and sanctuaries and to support zoos. China followed suit and is producing Panda Poo Paper.

2. Cure

When the German army occupied northern Africa during World War II, many soldiers suffered terribly from dysentery, but residents of the area seemed to take it in stride. The Germans found that as soon as the first symptoms of dysentery were noticed, the locals followed a camel and collected its poop as soon as it dropped. Then they ate it. It cured the dysentery, but only if it was fresh. The secret was the beneficial bacteria (Bacillus subtilis) in the camel dung, which aided digestion and crowded out disease bacteria. You can imagine the horror of the fastidious Germans when they discovered what the cure was. Still, it was better than dying. The German medical corps found a way to isolate the bacteria for the ailing soldiers. Keep reading, the story gets better. Image by Flickr user VÃ­t Hassan.

3. Camouflage

Camel "apples" became a good luck charm for the German military. The Allies discovered their habit of intentionally running tanks over piles of the droppings for good luck. So the Allies developed and planted land mines that looked like camel dung! When the Germans caught on to the trick, they began to avoid fresh piles of camel manure. In turn, the Allies caught on and began to make mines that looked like camel dung that had already been run over by a tank and therefore seemed safe enough to a Nazi driver. Genius.

4. Coffee

The most expensive coffee in the world comes from poop. The Asian Palm Civet is a small animal that loves to eat coffee cherries, if it is lucky enough to live on the Indonesian islands where coffee is grown. The cherries only partially digest and are excreted fairly intact. The poop is gathered and washed, and the coffee beans are sold as Kopi Luwak, which can cost hundreds of dollars per pound. The partial digestion process is supposed to add a wonderful flavor to the coffee. Kopi Luwak is also produced in the Philippines and in East Timor. Image by Wie146.

5. Gunpowder

Guano is the polite word for sea bird droppings, and also refers to bat and seal waste. The term came into use in South America to refer to mineral deposits mined from islands off the Peruvian coast. Guano is full of nitrogen, particularly potassium nitrate used for gunpowder, and phosphorus used for fertilizer. Lack of predators allowed birds to poop on these islands for thousands of years, and the lack of rainfall preserved the guano, leaving dried deposits up to 150 feet deep! The War of the Pacific was fought partially over guano mining rights. Chile, Bolivia and Peru all wanted to exploit the minerals of the Atacama Desert on the west coast of South America, which included saltpeter for explosives and guano for fertilizer and gunpowder.

6. Clean Water

A side effect of tin and silver mining in Bolivia is the acid water laden with dissolved metal that leaches from the mines. The toxic runoff pollutes water as it drains away, killing algae and fish. What to do? One method of cleaning the water is to introduce bacteria that process sulfates in the water, essentially binding the dissolved metals into iron sulfide, zinc sulfide, etc. so that the metals drop to the bottom of the water. This bacteria is introduced by adding llama dung to water treatment lagoons and wetlands, a method developed in Britain using cow and horse manure. Image by Flickr user Jessie Reeder.

7. Energy

Humans have fueled their fires with animal dung since fire was invented, but now this energy source is beginning to be harvested on a large scale. It just makes sense, as huge industrial feedlots produce tons of the stuff. Solid manure can be burned, and liquid manure produces biogas, which is about 60% methane, or natural gas. Projects are underway to tap sources of chicken manure for electrical energy, cow manure to heat homes, and pig manure to fuel up cars. Image by Flickr user NIOSH.