Cotton Production

“Cotton production

The production of cotton is generally efficient, with less than 10 percent of the picked weight lost in the subsequent processes of converting the raw cotton bolls (seed cases) into pure fibre.

Harvesting

One hundred million rural households around the world are involved in cotton production, the majority of which happens within the  developing world where cotton continues to be picked by hand. In Europe, Australia and the United States, on the other hand, it is mechanically harvested by one of two types of harvesting machine, depending on the cotton variety grown. A cotton picker removes the cotton from the boll without damaging the plant, while a cotton stripper machine strips the entire boll from the plant. Strippers are used in climatic regions that are too windy to grow the ‘picker’ varieties of cotton.

In some cases a chemical defoliant is first used to remove the leave; alternatively natural defoliation would occur after a temperature freeze.

After harvesting the land is tilled. The conventional method is to cut down the reaming stalks and turn the soil ready for the next round of seed planting. The alternative method, known as the ‘conservation method’, leaves the stalks and the plant residue standing on the surface of the soil, and the new seeds are planted through the ‘litter’ that remains.

After harvesting a machine known as a module builder compresses the cotton into large modular blocks that are covered and temporarily stored in the fields. These are collected by specially designed trucks and transported to the gin.

Ginning

Ginning is the generic term used for the complete process of turning the cotton bolls into fibre, and the building in which these processes occur is referred to as the gin. The name was originally used as an abbreviation of the word ‘engine’, and is now part of cotton vocabulary. At this stage, and until the ginning process has been completed, the cotton is referred to as seed cotton.

Once the cotton blocks have been delivered to the gin they are broken apart and fed into the ginning macvhine, which efficiently separates the cotton fibres from the seedpods, removing leaves, burs, dirt, stems and the fuzzy down known as linters. Usable cotton fibres will make up about 35 per cent of the re-ginned cotton weight. The balkance of the pre-ginned weight is mede up from 55 per cent removed seeds and 10 per cent waste. The seeds are refined and made into cottonseed oil for human consumption. The linters are used in the manufacture of paper, as well as within the plastics industry.

The ginning machine also cleans the cotton, which is now referred to as lint instead of seed cotton.”…

“Processing and spinning

Once processed to remove traces of wax, protein and seeds, cotton fibre consists of nearly pure cellulose, which is a natural polymer. The arrangement of the cellulose is such that it gives cotton fibres a high degree of strength, absorbency and durability. Each fibre is made up of between 20 to 30 layers of cellulose coiled in a neat series of natural springs. The fibres of the open boll dry into flat, twisted, ribbon-like shapes that become kinked and interlock together. It is this interlocked form that is ideal for spinning into fine yarn.

Spinning is a generic term for all the processes the fibres will pass through to become yarn, ready for eventual weaving or knitting.

Once at the spinning mill, which may also be referred to as the ‘spinners’, the bales are opened and further cleaned to remove any residue vegetable matter and short lint. A machine called a picker beats, loosens and mixes the fibres, which are then passed through toothed rollers of varying sizes to remove the residue vegetable matter. The fibres finally come off the machine in batts, large bundles of multiple strands of fibres, which are then ready to be carded. The short lint is sold on for other processes and end uses.

The carding machine lines up the fibres evenly to make them easier to spin. This is done by passing the batts through different-sized rollers tat produce what is termed slivers(pronounced sly-vers), or untwisted ropes of fibres. Several slivers are then combined to equalize the thicker and thinner parts of the slivers, thus making a more consistent size. These are now too thick, so are separated into rovings, long narrow bundles of fibre with twist to hold them together.

In addition to carding, fibres can also go through an optional combing process to make them smoother.”…

“Ecological and ethical considerations

The increasing demand for cotton at competitive prices has resulted in what may be considered mass-exploitation of poor cotton farmers and the land upon which cotton is cultivated. However, there are laternatives that allow the consumer to choose a product from an ethically and environmentally sound source.

Approximately 30 per cent of the cotton harvested and knitted for T-shirt production is shipped to a second country for manufacturing, impacting on cotton’s carbon footprint.

Some cotton cultivation is known to make use of a variety of pesticides and insecticides. These are especially prevalent in the developing world and some sources attribute deaths within the cotton industry to their use. Cotton Incorporated is a company with offices worldwide that offers extensive information regarding all aspects of cotton, from farming and ‘green issues’ to design and manufacturing. It also has a extensive list of fabric resources.

The American and Australian cotton industries have invested in biotechnology to try to combat the excessive use of insecticides associated with standard commercial cotton production. However, this has resulted in much of the cotton grown today being GM cotton.

There are two types of GM, or transgenic, cotton in use, Bollgard is obtained from a naturally occurring soil bacterium, Bacillus thuringiensis, referred to as Bt cotton. This naturally occurring soil organism is used as a spray, which reduces the use in insecticides by up to 85 per cent compared to conventionally grown cotton. It gives the plant an in- built tolerance to its main pest, the Heliothis caterpillar, and in North America the boll weevil. The alternative product is Roundup Ready, which is obtained from the soil bacterium Agrobacterium tumefaciens. This herbicide-tolerant cotton reduces the amount of soil cultivation and herbicides needed to control weeds. It also promotes healthier soil through less disruption a reduction in herbicide residues.

Organic cotton

GM cotton shares with organic cotton the same issue of chemical usage in the growing cycle, however the similarities stop there as organic cotton has a completely different ethos.

Slowly but steadily ther are now a growing number of farmers moving towards a mor organic, ecologically sound and socially sustainable method of production. Orgainc agricultural methods rely upon crop rotation and the use of natural enemies, such as ladybirds to suppress harmful insects, rather than the use of agrochemicals, artificial fertilizers and other toxic-persistent chemicals. Organic cotton does not use genetically modified organisms but seeks to build a biologically diverse agricultural system, replenishing and maintain the soil’s fertility.

Organic cotton is far more expensive to produce; however it does not pollute and there is no over-production. Unfortunately, currently it only represents a small percentage of global cotton production.

Organic cotton is grown in around 20 countries, with Turkey the primary producer. The United States, India, Peru, Uganda, Egypt, Senegal, Tanzania, China and Israel also produce organic cotton”.

“Water

Cotton is a thirsty crop, a fact that is fast presenting problems to countries whose economic growth overly relies upon the cotton industry but whose geographical position suffers from water shortages. Uzbekistan and Kazakhstan, both once part of the former Soviet Union, have in parts been turned into a desert through the excessive cultivation of cotton, which in turn has also led to the shrinking of the Aral Sea.

Developments are now being made in the cultivation of new plant varieties that include drought-resistant, flame-resistant and wrinkle-free genetically modified cotton”.

Segments from the book, “Fabric for Fashion” by Clive Hallett and Amanda Johnston, 2010. - posted by Alice