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EDIPTEX - Environmental assessment of textiles

Annex 9: Data for spinning

• Energy consumption
  • Company data for spinning processes
• List of references for spinning

This paper covers ring spinning and OE spinning of cotton or synthetic fibres or blends thereof in the cotton system. The references in this annex's list of references form the basis of this paper.

Yarns are divided according to two functions: yarns for knitwear and woven yarns. Manufacture of spun knitwear yarns and weaving yarns from the same fibre type is very similar within the individual spinning systems. Roughly speaking, the only difference in manufacture is the number of twists (ply) applied towards the end of the manufacturing process. Knitwear yarns have the lowest number of twists. This means that a production line set up for knitwear yarns is relatively easy to convert to production of weaving yarns. This is not done in practice due to production speed considerations.

There are relatively few important environmental aspects to consider for a spinning mill in an lifecycle assessment context. These include:

• Energy consumption for the spinning line and for air conditioning (air humidity and temperature)
• Fibre waste during spinning processes
• Any use of spindle oils for the spinning processes
• Cotton dust - may cause the lung disease Byssinosis

Energy consumption

Calculations for electricity consumption have been made on the basis of Hammond et al., 1980 and are shown in table 9.1 below.

Table 9.1 Electricity consumption (all energy data for processes in kWh per kg spun yarn)

*(1): The reason these figures are different is that it does not take the same amount of time to produce one kg of the different types of yarn.

Company data for spinning processes

The figures in the above table differ somewhat from the company data (De Danske Bomuldsspinderier - Danish cotton spinning mills):

Energy consumption is calculated according to the following formulas based on experience:

• Ring yarn 100 per cent synthetic (in MJ/kg): E = 3.6 * (0.6 + 0.05 * (75-tex)), tex-interval 13 - 60, i.e. E = (5 - 13MJ/kg)
• Combed ring yarn 65/35 Polyester/cotton: E = 3.6 * (0.75 + 0.05 * (80-tex)), tex-interval 13 - 60, i.e. E = (6 - 15MJ/kg)
• Combed 100 per cent cotton, ring yarn: E = 3.6 * (0.8 + 0.05 * (80-tex)), tex-interval 13 - 60, i.e. E = (6 - 15MJ/kg)

For all yarn types, the conditioning system uses:

• Energy: natural gas 0.017 Nm³/kg i.e. with 38.9 MJ/m³ approx. 0.6 MJ/kg
• Water: 2.2 litres/kg

As can be seen, the company figures are very similar to those from the literature.

From manufacture of carded cotton, there is about 15 per cent waste and about 9 per cent waste from carded synthetic. For combed cotton, there is about 30 per cent waste (15 per cent from combing alone, figures from Roberts (1980)). Particularly during manufacture of combed cotton and synthetic, it is possible to use the fibre waste for lower quality yarn. However, we have decided to assume that the fibre waste is not recirculated, as not enough information is available to estimate the proportion of recyclable waste.

No spindle oils are used to spin cotton. Spindle oils may be used at the spinning mill to spin synthetic, but it is more common to apply spindle oil to the synthetic fibres during fibre production.

There is currently no data for dust at cotton spinning mills.

List of references for spinning

Hammond N., et al., 1980. Energy consumption in yarn manufacturing processes. Paper presented at the 12th Shirley International Seminar 16-18 September 1980. Shirley Institute Publication S40.

Roberts, DR. J.G., 1980. Energy audits. Paper presented at the 12th Shirley International Seminar 16-18 September 1980. Shirley Institute Publication S40.

Personal talks, 1999, with Anders Hedegaard, De Danske Bomuldsspinderier A/S.

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Version 1.0 July 2007, © Danish Environmental Protection Agency