Leather
Abundance
Interestingly, there is no good figure for the amount of leather produced annually. While many sources tout the statistic that one cow hide can produce 15-25 NFL footballs, no online source seems to have a good estimate of just how much leather is produced, or what percentage of clothing fiber is leather.
History
Leather, or rudimentary leather, has been worn just about as long as humans have existed. Perhaps longer. Every culture, from ancient Egypt to the Native Americans, to the Asian populations, was proficient in leather making [1]. However, we have come a long way from chewing the hides of our prey to make them supple and wearable, treating our modern leather with all sorts of chemicals depending on the desired finished look and properties of the ultimate product.
Manufacturing
Leather can be made in many different ways. In more third world countries, the leather making process is not mechanized (see picture of Moroccan tannery). However, in most of the modern world, the process is almost entirely mechanized.
Interestingly, there is no good figure for the amount of leather produced annually. While many sources tout the statistic that one cow hide can produce 15-25 NFL footballs, no online source seems to have a good estimate of just how much leather is produced, or what percentage of clothing fiber is leather.
History
Leather, or rudimentary leather, has been worn just about as long as humans have existed. Perhaps longer. Every culture, from ancient Egypt to the Native Americans, to the Asian populations, was proficient in leather making [1]. However, we have come a long way from chewing the hides of our prey to make them supple and wearable, treating our modern leather with all sorts of chemicals depending on the desired finished look and properties of the ultimate product.
Manufacturing
Leather can be made in many different ways. In more third world countries, the leather making process is not mechanized (see picture of Moroccan tannery). However, in most of the modern world, the process is almost entirely mechanized.
1) The hide is cut in half for ease of handling.
2) Hides are then moved to a massive rotating cylinder, where hair is removed during a chemical process in which an alkali solution breaks down the hair structure at the root [2].
3) Sulphide is then added to the above solution, causing the collagen in the skin to swell and become more open (depending on the manufacturer, this may have been added with the alkali solution).
4) The skins are then treated with enzymes to get rid of any more unwanted material, as well as make the skin more porous.
5) Then, the skins are bathed in acid to preserve them, and prime them for absorbing salts
6) The subsequent tanning happens in massive wooden drums, with prongs to stop the hides from getting tangled [3]. Complex chromium ion salts turn the skin a shade of blue as a result of the chromium binding to collagen fibers in the skin.
7) The hides are now considered leather, and are much more supple and durable.
8) The leather, grain side up, is split into layers. Another machine slices the leather on the flesh side to an even thickness, and cut offs are recycled into suede.
9) The uniformly thick layers of leather are then placed back into wooden drums for a second tanning, but this time, the chemicals stabilize the still reactive chromium and make the leather even softer by using vegetable extracts, tree bark, water, dye, and chemicals to make it water resistant. Often, the leather is dyed at this stage.
10) To dry the nearly finished product, starch and water solutions are brushed onto tanned hides that allow them to stick onto glass to dry flat as they are rolled into drying rooms.
11) After four hours in the dryer, the leather is sprayed with dye to enhance the color.
12) To polish the leather, an abrasive glass glazing jack is run rapidly over the leather.
13) Finally, heated rolls are run over the leather to smooth out any wrinkles, and the leather is now ready to be made into its ultimate product.
Environmental Impacts
There is great controversy surrounding the production of leather. On the one hand, leather is much more durable than many fabrics on the market, making it more environmentally friendly if leather pieces are kept and maintained for many, many years. This is a scenario in which one leather product would take the place of several synthetic products that, unlike leather, are not biodegradable. On the other hand, we must bear in mind that leather is ultimately a wonderful resource if it is being taken responsibly. Unfortunately, the simple fact is that the meat and dairy industries are so out of proportion that no matter how their hides are treated, the sheer number of cows living on the earth is causing irreparable damage to both the ozone and habitats destroyed to make room for them.
Taking the manufacturing process into account, leather becomes an even dirtier fabric. It is estimated that for every one ton of hide, 20-80 cubic meters of wastewater with chromium levels of 100-400 mg/L, sulfide levels of 200-800 mg/L, and high levels of fat and solid wastes are produced [4]. In addition, solid wastes can represent up to 70% of the wet weight of the original hides, causing huge strain on water filtration systems in place [4].
In places where water filtration is lax or nonexistent, such as tanneries on the Ganges river in India in 2003, 22 tons of untreated chromium-laden solid waste were dumped into the river every day [5]. This has made large parts of the river unusable, and has wrought havoc on the aquatic ecosystem as well as ecosystems around it.
What You Can Do
Try not to buy leather products unless there is no long-lasting, sustainable alternative. Eat less meat, especially beef. The leather industry is driven by the beef and dairy industry, and by modifying what we eat we will be able to see a much healthier planet. Less habitat will be destroyed to make grasslands for cows, and greenhouse gas emissions would noticeably decrease.
2) Hides are then moved to a massive rotating cylinder, where hair is removed during a chemical process in which an alkali solution breaks down the hair structure at the root [2].
3) Sulphide is then added to the above solution, causing the collagen in the skin to swell and become more open (depending on the manufacturer, this may have been added with the alkali solution).
4) The skins are then treated with enzymes to get rid of any more unwanted material, as well as make the skin more porous.
5) Then, the skins are bathed in acid to preserve them, and prime them for absorbing salts
6) The subsequent tanning happens in massive wooden drums, with prongs to stop the hides from getting tangled [3]. Complex chromium ion salts turn the skin a shade of blue as a result of the chromium binding to collagen fibers in the skin.
7) The hides are now considered leather, and are much more supple and durable.
8) The leather, grain side up, is split into layers. Another machine slices the leather on the flesh side to an even thickness, and cut offs are recycled into suede.
9) The uniformly thick layers of leather are then placed back into wooden drums for a second tanning, but this time, the chemicals stabilize the still reactive chromium and make the leather even softer by using vegetable extracts, tree bark, water, dye, and chemicals to make it water resistant. Often, the leather is dyed at this stage.
10) To dry the nearly finished product, starch and water solutions are brushed onto tanned hides that allow them to stick onto glass to dry flat as they are rolled into drying rooms.
11) After four hours in the dryer, the leather is sprayed with dye to enhance the color.
12) To polish the leather, an abrasive glass glazing jack is run rapidly over the leather.
13) Finally, heated rolls are run over the leather to smooth out any wrinkles, and the leather is now ready to be made into its ultimate product.
Environmental Impacts
There is great controversy surrounding the production of leather. On the one hand, leather is much more durable than many fabrics on the market, making it more environmentally friendly if leather pieces are kept and maintained for many, many years. This is a scenario in which one leather product would take the place of several synthetic products that, unlike leather, are not biodegradable. On the other hand, we must bear in mind that leather is ultimately a wonderful resource if it is being taken responsibly. Unfortunately, the simple fact is that the meat and dairy industries are so out of proportion that no matter how their hides are treated, the sheer number of cows living on the earth is causing irreparable damage to both the ozone and habitats destroyed to make room for them.
Taking the manufacturing process into account, leather becomes an even dirtier fabric. It is estimated that for every one ton of hide, 20-80 cubic meters of wastewater with chromium levels of 100-400 mg/L, sulfide levels of 200-800 mg/L, and high levels of fat and solid wastes are produced [4]. In addition, solid wastes can represent up to 70% of the wet weight of the original hides, causing huge strain on water filtration systems in place [4].
In places where water filtration is lax or nonexistent, such as tanneries on the Ganges river in India in 2003, 22 tons of untreated chromium-laden solid waste were dumped into the river every day [5]. This has made large parts of the river unusable, and has wrought havoc on the aquatic ecosystem as well as ecosystems around it.
What You Can Do
Try not to buy leather products unless there is no long-lasting, sustainable alternative. Eat less meat, especially beef. The leather industry is driven by the beef and dairy industry, and by modifying what we eat we will be able to see a much healthier planet. Less habitat will be destroyed to make grasslands for cows, and greenhouse gas emissions would noticeably decrease.