The current price for bulls testicles is about USD2,000 per tonne. In North America they're crumbed and fried and sold as Rocky Mountain Oysters, Prairie Oysters or Sweetbreads. In China they're sold as "testosterone enhancers".

The only waste product not sold in an abattoir is the bloody, salty waste water used for skin packaging.

Apart from meat there are markets for intestinal guts (or sausage linings...once the faeces is removed), endocrine glands, hooves, horns, skins, fat, kidneys, faeces, wool, grease, blood, tongues, hearts, livers, brains and gallstones.

Gelatin which is found in bones, cartilage and tendons has been used for microscope culture plates and in cosmetics, paper money, pharmaceuticals, cakes, jellies, lollies, glues, vaccinations, photography and cinematography. It is an ancient process and is made from boiled animal tissue.

So how was gelatin used in photography? Up until the 1870s photography had relied upon wet development plates. Photographic paper was soaked in silver nitrate and saltwater baths. It was then placed wet into the camera. The exposed paper gave a dark silver image which had to be immediately washed to fix the image and remove the remaining silver chloride. It was a time consuming fiddly process. Photographers had to carry portable darkrooms and chemicals with them whenever they took photos. Then in 1871, English doctor Richard Maddox suggested a simple solution, the use of dry plates coated with an emulsion of gelatin and silver salts. The gelatin emulsion preserved the pictures. This meant the plates could be taken back to a darkroom much later, moistened and the pictures developed.

Gelatin is just a tiny part of the abattoir waste industry story. Bone China, as the name suggests, uses bone. Those fine cups on your grandmother's sideboard are made of bone ash, kaolin and China stone (a type of granite).

Then there's bull's testicles. If you're a US truck driver, you may well like them crumbed and fried and eaten as Rocky Mountain Oysters, Prairie Oysters or Sweetbreads. If you're a Chinese medicine customer they'll be ground and pulverised and sold to you as as a testosterone enhancer. The edible sort cost about USD2,000 per tonne whereas the pharmaceutical grade will cost about USD4,000 per tonne.

But the list doesn't end there. Apart from meat there are markets for intestinal guts. These are known in the trade as "runners"...or sausage linings. The faeces is squeezed out of the guts. They are then chilled and exported to China where they are thoroughly cleaned and then re-sold. The biggest market is Germany.

And so it goes on. There are scientists for instance using endocrine glands for research. Then there are markets for hooves, horns, skins, fat, faeces, kidneys, wool, blood, tongues, wool grease, hearts, liver, brains and gallstones. And for each of these products there are layers of complex and unexpected uses. Skins for instance are not only used for Ugg boots, rugs and coats. The wool is often shorn or chemically removed and used for carpets, underlay or coats. Athletes runners and luxury shoes frequently have bare sheepskin liners.

Finally there are gallstones. While every animal has a heart, kidneys and brain, gallstones are comparatively rare and valued as an antipyretic in Chinese medicine. These are frequently the illicit province of abattoir shift supervisors who slip them into an esky and sell them for about USD35 each to Chinese herbal medicine suppliers.