Comparison of methodologies for LCA processes

- Application to the dyeing of cotton

• Vanessa Pasquet • Sandrine Pesnel • Anne Perwuelz • Nemeshwaree Behary

GEMTEX: university research laboratory in the field of textile materials and processes

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• Interreg IV project between Southern Belgium and Nord – Pas-de-Calais region (end in 2012)

• 4 members :

• Main lines :

– Realisation of Life Cycle Assessment (LCA)

– Implement the Best Available Technologies (BAT)

– Help for the REACH legislation

– Recycling of co-products

ACVTEX project

www.acvtex.eu

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Problem of cotton dyeing industry

WaterChemicals (Dyes, surfactants, etc..)

ElectricityThermal energie

Dyed textile

Dyeing process

Emissions inWater, air and soil

Waste

Cotton dyeing involves high water consumption, energy use and also input of a wide range of chemicals.

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Cotton dyes

Cotton fiber can be dyed with 4 different dyes: • Reactive, • Direct, • Vat, • Sulfur

Objectives: • Compare different cotton dyeing processes with LCA processes

• Focus on the modeling of water emissions and water

treatments

Each class of dye involves different process in terms of bath temperature, time of treatment and chemicals used.

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Laboratory tests

0

2

4

6

8

10

12

14

16

18

20

0 5 10 15

K/S

max

dye (%)

Vat

Reactive

Direct

Sulphur dye

Indigo (natural vat)

Methodology to determine the fonctional unit:

We performed tests in lab to ensure the similar properties in terms of

colour strength (given by K/S values) and dyeing durabilities of 5 dyes

processes.

Colour strength values of dyed fabric according to the % of dye

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LCA of processes - Methodology

Software : GaBi (PE International AG) Data sources: lab tests, theoretical values for energies consumption, databases of Gabi and ELCD for generic data and publications for the production of indigo Calculation of the impacts: ReCiPe method (mid point)

Functional unit: “to dye 1 kg cotton fabric with a colour strength given by a K/Smax value of 8 and good rubbing and washing durabilities ”

Electricity production

Chemical production

Water softening

Thermal energy production Dyeing+ rinsesDrying

Finishing

Scouring

Waste water treatment

System boundary

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LCA of processes - results

0102030405060708090

100%

Reactive Direct synthetic vat Indigo Sulphur

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LCA of processes - results

• Dyeing with natural indigo dye -> highest environmental impact Due to the high impact of the agro-sourced dye production.

0102030405060708090

100%

Reactive Direct synthetic vat Indigo Sulphur

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LCA of processes - results

• Dyeing processes with the synthetic reactive and direct dyes are more beneficial than vat or sulfur dyes Due to the lower dyeing temperature, shorter dyeing time, less auxiliary products and less number of rinses required.

0

10

20

30

40

50

60

70

80%

Reactive Direct synthetic vat Sulphur

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Sensitivity analysis - colour

The results can not be extrapolated to another colour intensity. Dyeing processes associated with dark, pale and normal shades, for the reactive dye only were compared. -> Bleaching step with clear tones before dyeing

020406080

100120140

CC [kg CO2-Equiv.]

FD [kg oil eq]

FE [kg P eq]

HT [kg 1,4-DB eq]

IR [kg U235 eq]

ME [kg N-Equiv.]

MD [kg Fe eq]

WD [m3]

Clear tone Bleaching + clear tone Midtone Dark tone

Pale shades is 19 % less than that of normal or dark shades. The additional bleaching step leads to an increase in impact categories Caused mainly by the production of the oxidizing agent used.

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Electricity production

Chemical production

Water softening

Thermal energy production Dyeing+ rinsesDrying

Finishing

Scouring

Waste water treatment

System boundary

Sensitivity analysis – Water treatment

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Sensitivity analysis – Water treatment

Scenarios Emissions into water Modelization of the wastewater

treatment

No emission No emission No wastewater treatment

COD output COD (measured) output No wastewater treatment

Molecules output

List of molecules into effluent in output

No wastewater treatment

Municipal station

No emission Presence of a municipal wastewater

treatment

Textile station No emission Presence of textile specific wastewater

treatment

Textile station + COD rate

No emission Presence of textile specific wastewater treatment with COD abatement rate

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Sensitivity analysis – Water treatment

Scenarios Emissions into water Modelization of the wastewater

treatment

No emission No emission No wastewater treatment

COD output COD (measured) output No wastewater treatment

Molecules output

List of molecules into effluent in output

No wastewater treatment

Municipal station

No emission Presence of a municipal wastewater

treatment

Textile station No emission Presence of textile specific wastewater

treatment

Textile station + COD rate

No emission Presence of textile specific wastewater treatment with COD abatement rate

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Sensitivity analysis – Water treatment

Scenarios Emissions into water Modelization of the wastewater

treatment

No emission No emission No wastewater treatment

COD output COD (measured) output No wastewater treatment

Molecules output

List of molecules into effluent in output

No wastewater treatment

Municipal station

No emission Presence of a municipal wastewater

treatment

Textile station No emission Presence of textile specific wastewater

treatment

Textile station + COD rate

No emission Presence of textile specific wastewater treatment with COD abatement rate

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Sensitivity analysis – Water treatment

0

0,001

0,002

0,003

0,004

0,005

[kg

N -

eq

]

ReCiPe Midpoint (H) - Marine eutrophication

0,00E+00

5,00E-07

1,00E-06

1,50E-06

2,00E-06

2,50E-06

3,00E-06

[kg

P eq

]

ReCiPe Midpoint (H) - Freshwater eutrophication

0

0,001

0,002

0,003

0,004

0,005

0,006

0,007

0,008

0,009

[kg

N -

eq

]

TRACI, Eutrophication

0

0,0005

0,001

0,0015

0,002

0,0025

0,003

0,0035

0,004

[kg

Ph

osp

ha

te-E

qu

iv.]

CML2001 - Nov. 09, Eutrophication Potential (EP)

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Sensitivity analysis – Water treatment

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Sensitivity analysis – Water treatment

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Sensitivity analysis – Water treatment

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• Quality aspects of dyeing processes have to be taken into account in the functional unit .

• Modeling of effluents and wastewater treatment has a considerable influence on the impacts.

• Some dyes are toxic for humans, their cytotoxicity should be evaluated and include in the comparison.

• Lifetime of a dyeing according to durability tests should be taken into account in a LCA of product.

Discussion of the method

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Conclusions

• Natural dye production step is polluting > Necessity for Eco-design culture and extraction of these dyes • Reactive and direct dyes are quite interesting from an environmental point of view comparing to vat and sulphur dyes. • Study different machines with different liquor ratios, energy consumption could also be realized to compare cotton dyeing processes.