Could the recycled yarns substitute for the virgin cotton yarns: a comparative LCA

Abstract

PurposeCotton yarns spun from natural fibers are widely used in the apparel industry. Most of waste cotton goods are now disposed by incineration or landfill, which brings resource and environmental challenges to the society. Using the waste cotton to spin yarns is an alternative way to forward a more sustainable future. In this research, two scenarios for the environmental impacts of yarns spun from corresponding fibers are investigated, including recycled cotton fibers and virgin cotton fibers.Methods
The life cycle assessment (LCA) has been conducted according to the collected data from on-site investigation of typical production factories. The life cycle for the recycled cotton yarn production is divided into five stages, i.e., raw material acquisition, transportation, breaking, mixing, and spinning. The life cycle of virgin cotton yarn production is been divided into four stages, i.e., raw material acquisition, transportation, mixing, and spinning. The functional unit is 1000 kg produced yarns which are used for weaving into the fabrics. Notable impacts on climate change, fossil depletion, water depletion, and human toxicity were observed.ResultsThe life cycle impact assessment (LCIA) results show that environmental impacts of recycled cotton yarns are far less than those of virgin cotton yarns, except for climate change and water depletion. The reason is that the land occupation and irrigation water have great impact on environmental impacts of cotton cultivation. In spinning, the electricity is the key factor whose environmental impacts account for the most in the virgin cotton yarn scenario, while the electricity and water consumptions are the key factors for the recycled cotton yarn scenario in the life cycle of yarn production. The sensitivity analysis indicates that improving energy efficiency can significantly reduce environmental burdens for both the two scenarios. The uncertainty distribution of water depletion, human toxicity, fossil depletion, and climate change of the two scenarios were determined with a 90% confidence interval.Conclusions
The LCIA results reveal recycled cotton yarn is a viable alternative to relieve resource and environmental pressure. About 0.5 ha of agricultural land can be saved, 6600 kg CO2 eq can be reduced, and 2783 m3 irrigation water can be saved by using 1000 kg of the recycled cotton yarns. It can be concluded that the recycled cotton fibers can be served as a substitute for virgin cotton fibers to reduce agricultural land and avoid environmental impacts generated from the cotton planting.

Full text

LIFE CYCLE SUSTAINABILITY ASSESSMENT
Could the recycled yarns substitute for the virgin cotton yarns:
acomparativeLCA
Yun Liu
1,2
&Haihong Huang
1,2
&Libin Zhu
1,2
&Cheng Zhang
3
&Feiyue Ren
1,2
&Zhifeng Liu
1,2
Received: 18 January 2020 /Accepted: 17 August 2020
#Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract
Purpose Cotton yarns spun from natural fibers are widely used in the apparel industry. Most of waste cotton goods are now
disposed by incineration or landfill, which brings resource and environmental challenges to the society. Using the waste cotton to
spin yarns is an alternative way to forward a more sustainable future. In this research, two scenarios for the environmental impacts
of yarns spun from corresponding fibers are investigated, including recycled cotton fibers and virgin cotton fibers.
Methods The life cycle assessment (LCA) has been conducted according to the collected data from on-site investigation of
typical production factories. The life cycle for the recycled cotton yarn production is divided into five stages, i.e., raw material
acquisition, transportation, breaking, mixing, and spinning. The life cycle of virgin cotton yarn production is been divided into
four stages, i.e., raw material acquisition, transportation, mixing, and spinning. The functional unit is 1000 kg produced yarns
which are used for weaving into the fabrics. Notable impacts on climate change, fossil depletion, water depletion, and human
toxicity were observed.
Results The life cycle impact assessment (LCIA) results show that environmental impacts of recycled cotton yarns are far less
than those of virgin cotton yarns, except for climate change and water depletion. The reason is that the land occupation and
irrigation water have great impact on environmental impacts of cotton cultivation. In spinning, the electricity is the key factor
whose environmental impacts account for the most in the virgin cotton yarn scenario, while the electricity and water consump-
tions are the key factors for the recycled cotton yarn scenario in the lifecycle of yarn production. The sensitivity analysisindicates
that improving energy efficiency can significantly reduce environmental burdens for both the two scenarios. The uncertainty
distribution of water depletion, human toxicity, fossil depletion, and climate change of the two scenarios were determined with a
90% confidence interval.
Conclusions The LCIA results reveal recycled cotton yarn is a viable alternative to relieve resource and environmental pressure.
About 0.5 ha of agricultural land can be saved, 6600 kg CO
2
eq can be reduced, and 2783 m
3
irrigation water can be saved by
using 1000 kg of the recycled cotton yarns. It can be concluded that the recycled cotton fibers can be served as a substitute for
virgin cotton fibers to reduce agricultural land and avoid environmental impacts generated from the cotton planting.
Keywords Life cycle assessment .Environmental impact .Virgin cotton yarns .Recycled cotton yarns .Spinning
1 Introduction
Cotton is one of the most important crops in the world and it
plays a vital role in national economic growth. Cotton fibers, a
type of natural fibers, are widely used in apparel industry. In
2015, 5.6 × 10
9
kg cotton fibers were produced and more than
3.5 × 10
6
ha agricultural land were used for cotton planting in
China (National Bureau of Statistics 2017). The large-scale
consumption of cotton in China has become a non-
negligible challenge to agricultural land occupation.
Moreover, a large number of cotton fibers are consumed in
the apparel industry each year, which results in considerable
Responsible editor: Zuoren Nie
*Haihong Huang
huanghaihong@hfut.edu.cn
1
School of Mechanical Engineering, Hefei University of Technology,
193 Tunxi Road, Hefei 230009, People’sRepublicofChina
2
Key Laboratory of Green Design and Manufacturing of Mechanical
Industry, Hefei University of Technology, 193 Tunxi Road,
Hefei 230009, People’sRepublicofChina
3
School of Mechanical Engineering, Nantong University, 9 Seyuan
Road, Nantong 226019, People’s Republic of China
The International Journal of Life Cycle Assessment
https://doi.org/10.1007/s11367-020-01815-8

waste cotton goods are produced. As the largest producer and
exporter of textiles in the world, 3.4 × 10
10
kg of yarns and 8.9
×10
9
meters of fabrics were produced in China in 2014
(National Bureau of Statistics 2019) and there was a little
utilization rate of recycled cotton fibers. About 87% of the
waste cotton fabrics were treated by incineration or landfill
(Chinese Academy of Engineering. 2018). Thus, development
of waste cotton fibers has great significance for improving
environmental performance, and the way that how to treat
waste cotton goods becomes an environmental challenge to
the society. In the context of economic issues and environ-
mental protection, it is necessary to seek a substitute for the
cotton fibers in the apparel industry to mitigate environmental
burdens. The recycled cotton fibers have attracted much atten-
tion because of their economic value and environmental
performance.
Many researchers focused on the application of waste cot-
ton products and addition economic value. The textile waste
primarily can be recycled in the form of reuse and conversion
into low-value or value-added products. Some innovative
products are developed from recycled fibers, like insulation
materials for acoustics, recycled polyester fabrics for uni-
forms, and heavy-duty canvas material (Ahmad et al. 2016).
Wanassi et al. (2016) have reported that waste yarns can pro-
duce a new low-cost yarn that has similar physical and me-
chanical properties comparing with 100% cotton yarn.
According to the research of Pegoretti et al. (2014), the
recycled cotton fibers were applied to acoustic automotive
components in the Brazilian automotive sector. Wang et al.
(2017) confirmed that the high-value cellulose nanocrystals
obtained from waste cotton cloth exhibited a high crystallinity
index. The cotton waste was also utilized to make building
materials, which helps in solid waste management and gener-
ates additional revenue (Rajput et al. 2012). Therefore,
the recycled cotton can be applied to various products because
of certain addition economic value.
The environmental performance of recycled cotton fibers
has also attracted much attention. Sandin and Peters (2018)
provide strong support for claims that textile reuse and
recycling reduce environmental impact compared with incin-
eration and landfilling, which based on a summary of forty-
one studies. Since there is no textile recycling plant in
Sweden, Zamani et al. (2014) have explored that the potential
environmental benefits of various textile recycling techniques
and it can save 1.0 × 10
4
kg CO
2
eq and 169 GJ of primary
energy through the integration of these recycling technologies.
A comparative life cycle assessment of recycled cotton has
been made by Esteve-Turrillas and De (2017); the results
show that high-quality textiles have advantages over environ-
mental impacts and electricity consumption when the recycled
cotton is applied to their production. The environmental im-
pacts associated with cotton cultivation and fibers dyeing are
avoided when recycled cotton fibers are obtained from cutting
textile wastes (Esteve-Turrillas and De 2017). The recycled
cotton fibers refrain from generating high amounts of waste-
water in dyeing plants (Roos and Peters 2015). As the
recycled cotton yarn is dyed before recycling, there is savings
in water, energy, dyes and auxiliaries, and effluent treatment
cost (Niinimäki and Hassi 2011). The recycled cotton fiber
was extracted from the denim cut waste by mechanical means
and blended with virgin cotton to produce recycled cotton
yarns using different blend ratios (Radhakrishnan and
Kumar 2018). This method of recycling denim cut waste is
adopted by some clothing companies, such as H&M, Adidas,
M&S. Thus, in terms of environmental impacts, the recycled
cotton certainly deserves more research attention for being
used as a feedstock in the apparel industry.
Due to the diversity of cotton textile products, it is difficult
to evaluate the environmental performance of per textile prod-
ucts (Liu et al. 2020). The environmental impacts of these
products can be evaluated by considering that of the compo-
sition of the products. These products are made up of the
fabrics and the fabrics are woven of yarns, and the yarns are
spun from the fibers. Moreover, the mechanical properties of
recycled cotton yarns are weaker than virgin cotton yarns
since the second use of the recycled cotton fibers. The
recycled cotton fibers are uniformly mixed with virgin fibers
in a certain proportion and spin to yarns (shown in Fig. 1).
Yarns are spun from different proportions of different fibers
that have different energy and resource consumptions.
Therefore, it is necessary to assess the environmental impacts
of yarns considering the recycled and virgin cotton fibers.
Summarized above, although the application of recycled
textile products has been investigated, the environmental per-
formance of virgin and recycled yarns, which can be woven
into varieties of textile products, has not been well studied so
far. Therefore, the paper focuses on evaluating the environ-
mental impacts of yarns spun from recycled cotton fibers and
virgin cotton fibers by using LCA methodologies. The LCA
for these yarns has great significance on evaluating the envi-
ronmental impacts of recycled yarn products and identifying
the opportunities to reduce their environmental impacts from
the beginning of product design. It can provide the quantita-
tive value to support the popularization of recycled cotton and
help to reduce the overall environmental impact in the apparel
industry.
2Methods
The study uses the “cradle-to-gate”approach to analyze envi-
ronmental impacts of the virgin cotton yarns and the recycled
cotton yarns. The life cycle for the recycled cotton yarn pro-
duction has been divided into five stages, i.e., raw material
acquisition, transportation, breaking, mixing, and spinning.
The life cycle of virgin cotton yarn production has been
Int J Life Cycle Assess

divided into four stages, i.e., raw material acquisition, trans-
portation, mixing, and spinning.
2.1 Goal of study
The goal of the study focuses onevaluating and comparing the
environmental impacts of the yarns spun from virgin cotton
fibers and the yarns spun from recycled cotton fibers. The
improvement opportunities from the manufacturer’sperspec-
tive are identified to support the popularization of recycled
cotton fibers. Fashion designers can then take environmental
performance into consideration when determining the material
design schemes during their works.
2.2 Functional unit
The functional unit (FU) of the product provides a quantified
reference for all relevant inputs and outputs in the LCA anal-
ysis. In this study, the FU is 1000 kg produced yarns which are
used for weaving into the fabrics. It provides the counting base
of all the process flows as the two systems consider yarn
production with the same use.
The mechanical properties of recycled cotton fibers are
weaker than virgin cotton fibers since the second use of the
recycled cotton fibers. Generally, the recycled cotton fibers
are uniformly mixed with virgin fibers in a certain proportion
and spun to yarns. In the context of small proportion of
recycled fibers which are mixed with virgin fibers for the
functional unit, the environmental impacts of fabrics can be
calculated by summing the environmental impacts of yarns
spun from different fibers.
2.3 System boundaries
Those system boundaries are established by the general pro-
cess of material inputs and pollution emissions to the environ-
ment. Note that the dyeing process is not included in recycled
cotton yarn scenarios because the colors of recycled cotton
fibersaredeterminedbythewastecottonproducts.
Moreover, in the related factories, the recycled cotton fibers
are uniformly mixed with other type fibers in a certain propor-
tion and spun to yarns. Since in this paper the dyeing process
is not included in the life cycle stages of recycled cotton yarns,
the process is not considered in virgin cotton yarn scenario
accordingly. Fig. 2describes the system boundaries of the two
scenarios.
The production flow of the virgin cotton yarn scenario
includes two main stages:
&The virgin cotton fibers are uniformly mixed. Considering
the environmental performance of cotton products, the
BCI (Better Cotton Initiative) cotton and organic cotton
may be adopted for decreasing the environmental impacts.
&The mixed fibers are finally spun into cotton yarns
through 10 processes in the spinning phase, including
picking, carding, combing, drawing, roving, spinning,
winding, packaging, dust elimination, and air condition.
The production flow of the recycled cotton yarn scenario
contains three main stages:
&The recycled cotton fabrics or yarns are broken through
five processes, i.e., washing, breaking, separating, open-
ing, and packaging.
&Recycled cotton fibers are uniformly mixed.
&The mixed recycled fibers are finally spun into recycled
cotton yarns through 10 processes that same as virgin
cotton yarn production.
2.4 Life cycle inventory
The LCA for yarns spun from virgin cotton fibers and
recycled cotton fibers are performed to evaluate environmen-
tal impacts on these yarns. The life cycle inventory (LCI) data
for the two scenarios are shown in Table 1.Alltheinputsand
outputs of the two scenarios are revealed in LCI table. The
inventory data are collected by on-site investigation of typical
production factories.
Fig. 1 The process of the fabrics
production that using virgin fibers
and recycled fibers
Int J Life Cycle Assess

2.4.1 Cotton cultivation
In the cotton cultivation stage, the survey on 10 farmers is
performed to collect the annual yield of cotton fibers, as well
as the consumption of fertilizers and pesticides. The result
shows that generally, 8–10 kg of the urea, 35–40 kg of com-
pound fertilizer, 0.8–1 kg of the pesticides, and 1.8–2.0 L of
fuel oil are required for gaining 100 kg of cotton fibers. The
compound fertilizer includes pure nitrogen, phosphorus pent-
oxide, and potassium oxide. The pesticides are used and
sprayed 4 times in the growth life of cotton.
Because of the residual effect after fertilizers and pesticides
used, the ammonia (NH
3
), nitrous oxide (N
2
O), and heavy
metal emissions are considered. According to the research of
Nemecek et al. (2014) and Khoshnevisan et al. (2018), the
model for calculating ammonia emissions and nitrous oxide
after the application of mineral fertilizers is incorporated in the
following equation:
NH3¼17=14ðÞ∑
M
m¼1
EFampNmin þEF bm1−pðÞNmin
ðÞ
ð1Þ
where NH
3
is ammonia emission after mineral fertilizer
application (kg NH
3
), mis the fertilizer type, Mis the
number of fertilizer types, EF
am
is an emission factor
onsoilswithpH<=7(kgNH
3
-N/kg N), EF
bm
is an
emission factor on soils with pH > 7 (kg NH
3
-N/kg N),
pis fraction of soils with pH < = 7 (%/100), and N
min
is a mineral fertilizer application (kg N).
Fig. 2 System boundaries: avirgin cotton yarn scenario, brecycled cotton yarn scenario
Int J Life Cycle Assess

N2O¼44=28ðÞð0:01
Ntot þNcr þ14=17ðÞNH3þ14=16ðÞNO2
ðÞ
þ0:0075 14=62ðÞNO2Þ
ð2Þ
where N
2
OisanemissionofN
2
O(kgN
2
Oha
-1
), N
tot
is total
nitrogen in mineral and organic fertilizer (kg N ha
-1
), N
cr
is nitro-
gen contained in the crop residues (kg N ha
-1
), NH
3
is the loss of
nitrogen in the form of ammonia (kg NH
3
ha
-1
), NO
x
is the loss of
nitrogen in the form of nitrogen oxides (kg NO
2
ha
-1
), and NO
3
is
the loss of nitrogen in the form of nitrate (kg NO
3
ha
-1
).
Mleach;i¼mleach ;iAið3Þ
where M
leach,i
is agricultural-related heavy metal iemission, m-
leach,i
is average amount of heavy metal emission, and A
i
is allo-
cation factor for the share of agricultural inputs in the total inputs
for heavy metal i.
Moreover, since the agricultural machinery can be used for
many times and has very long life, it is excluded in the LCA
analysis. The fuel oil consumed is considered in LCI. About 1.8–
2.0 L of fuel oil is required for gaining 100 kg of cotton fibers.
2.4.2 Fabrics/yarns breaking
In the fabrics/yarns breaking stage, these cotton fabrics/yarns
are washed before being broken. Those cotton fabrics/yarns
Table 1 Life cycle inventories of
yarns spun from virgin cotton
fiber and recycled cotton fiber
Processes Categories Unit Virgin cotton fiber Recycled cotton fiber
Cotton - Virgin cotton kg 1210 0
Input Planting Cotton see ds kg 4 0
Planting Urea kg 121 0
Planting Compound fertilizer kg 484 0
Planting Pesticides kg 12.1 0
Planting Fuel oil L 22.9 0
- Recycled fabrics/yarns kg 0 1450
Breaking Electricity kWh 0 157
Breaking Industrial water m
3
0 13.9
Breaking Cleaning agents kg 0 6
Breaking H
2
SO
4
(98%) kg 0 5.1
Breaking FeSO
4
kg 0 6
Breaking PAC kg 0 1.29
Breaking PAM kg 0 0.08
Breaking NaClO (10%) kg 0 10.5
Breaking Urea kg 0 0.04
Breaking Scale inhibitor kg 0 0.056
Breaking NaHSO
3
kg 0 0.056
Breaking NaOH (98%) kg 0 0.1
Breaking HCl (35%) kg 0 0.33
Mixing Electricity kWh 7 7
Spining Industrial water m
3
8.3 8.3
Spining Electricity kWh 3984 3984
Spining Cartons kg 77 77
Spining PE plastic belt kg 2.43 2.43
Output Planting NH
3
kg 32.03 0
Planting N
2
O kg 26.38 0
Planting Heavy metal (total) g 67.27 0
Breaking Solidified sludge kg 0 23.8
Breaking COD g 0 1675.9
Breaking Ammonium g 0 14.4
Breaking Phosphorus g 0 13.7
Breaking Anilines g 0 7.5
Breaking Suspended substance g 0 289.2
Breaking BOD
5
g 0 289.2
Breaking Chlorine dioxide g 0 1.04
Breaking AOX g 0 1.96
Breaking Chromium(+VI) g 0 0.11
Breaking Nitrogen g 0 63.6
Breaking Sulfide g 0 1.15
Breaking Antimony g 0 0.01
Product Spining Yarns kg 1000 1000
Spining By-product kg 210 210
*
PAC poly aluminum chloride, PAM polyacrylamide, COD chemical oxygen demand, BOD
5
biochemical oxy-
gen demand, AOX absorbable organic halogen
Int J Life Cycle Assess

are washed by the washing devices XGP-400, drying with
sunshine, and no ironing. The max capacity of washing device
is 400 kg and output power is 11 kW. The liquor-to-fabrics
ratio in washing process is 15:1.
The washing process is the main contributor to the water
consumption in this stage, which results in an equal volume of
wastewater. The wastewater is treated by the wastewater treat-
ment system, 36.3% of which is used as recycled water, and
the remaining is discharged to the municipal sewage treatment
plant after satisfying the required quality standards for dis-
charge (GB4287-2012. 2013) in China.
2.4.3 Mixing
In the mixing stage, two or more kinds of colored fibers were
fully mixed. The yarns offer a great variety of colors, and the
effect of mixing colors is formed by mixing different colored
fibers. The mixed ratio of colored fibers in melange yarn
products is between 0.5 and 100%. Since the color of recycled
cotton fibers is not considered when it is used secondly, the
color of virgin cotton fibers is also not considered in this
research.
Furthermore, considering the environmental performance
of cotton products, the BCI cotton, organic cotton, and com-
mon cotton may be adopted for decreasing the environmental
impacts. Moreover, the recovery mode and fiber types have
strong effect on the performance of recycled cotton yarns.
Thus, the cotton fibers are expected to be uniformly mixed
for improving the performance of the yarns.
2.4.4 Spinning
In the spinning stage, the yarns are generated by spinning the
fibers after the mixing stage. This stage has the largest energy
consumption compared with other phases. Notably, since the
two fibers have no effect on the processes and equipment
used, the energy and water consumption are the same in this
phase for the two fibers. Water is only consumed by air con-
ditioner which used to adjust humidity and temperature for
ensuring normal operation of the machines. The dust elimina-
tion devices are adopted for absorbing the dust generated from
the picking, carding, and combing, and the dust produced by
these processes can be absorbed by the dedusting devices, so
that the PM2.5 or PM10 in the workshop is same as outdoor.
Auxiliary processes are essential to guarantee its regular pro-
duction including lighting, handing, dust elimination, air com-
pressor, office, and other processes. In addition, during the
production of per function unit melange yarns, 0.21 t by-
products were produced according to the annual yield of yarns
in 2017. The environmental impacts of the by-products are
allocated to yarns according to the price of yarns and by-
products (Liu et al. 2020).
2.5 Data sources
The primary data of the two scenarios are taken from on-site
investigation of typical production factories. The factories
were located in Zhejiang province in China and the annual
production of cotton yarns was 2.1 × 10
7
kg in 2017. The
upstream data (i.e., the raw materials acquisition, transport,
and energy generation) are acquired from GABI database.
The coal-electricity is used for producing the yarns.
However, the industrialization production of recycled cotton
yarns has not been formed yet. This technique needs further
decreasing loss rate of the cotton fibers. In this research, the
recycled fibers are obtained by breaking 50% of waste fabrics
and 50% of waste yarns. The mass loss rate of the cotton fibers
is nearly 20% after the process of fabrics breaking. The waste
fabrics are obtained from the enterprise engaged in the recov-
ery of waste clothes and the waste yarns are leftover materials
of the yarn production in the related factories.
2.6 Assumptions
To facilitate the implementation of the LCA, some assump-
tions are made in this study and listed as follows:
&Human labor, packaging materials, device maintenance,
and administration overheads were excluded.
&The engineering construction and machines are not in-
cluded in the LCA system boundary, since the energy
and material data about factory buildings and machines
are difficult to obtain.
&The distance between the cotton cultivation origin in
Xinjiang province and the factory in Zhejiang province
is assumed to be 4650 km by truck (Google map). It
should be noted that the transportation distance is consid-
ered a constant in this research, since the environmental
impacts generated from the transportation (less 1% of total
environmental impacts) are small and the contributions of
cotton transportation to all impact categories are not sen-
sitive to the transportation distance in the whole life cycle
(Zhang et al. 2015).
&The average distance between the factory of yarn manu-
facturers and the enterprises located in the local or nearby
cities engaged in recovery of waste clothes is assumed to
be 100 km by truck.
2.7 Impact assessment
ReCiPe is an assessment method that allows performing the
study at an impact (mid-point) or damage (end-point) category
level (Goedkoop et al. 2013). The ReCiPe mid-point (H)
method was used for life cycle impact assessment (LCIA) of
two scenarios. The impact categories (15 categories) were
Int J Life Cycle Assess

considered based on LCI results, including climate change,
terrestrial acidification, freshwater eutrophication, marine eu-
trophication, ozone depletion, water depletion, metal deple-
tion, fossil depletion, freshwater ecotoxicity, marine
ecotoxicity, terrestrial ecotoxicity, human ecotoxicity, ioniz-
ing radiation, particulate matter formation, and photochemical
oxidant formation.
3 Result
3.1 LCIA results
The environmental impacts of all processes about the two
scenarios are calculated. The LCIA results of two scenarios
in all selected categories are presented in Table 2.
The impacts of two scenarios were mainly attributed to
climate change, fossil depletion, water depletion, and human
toxicity, whereas the remaining categories minimally contrib-
uted to the overall environmental burdens. Fig. 3presents the
relative contribution of each different life cycle stage to the
main impact category for the production of the yarn. The
potential impacts generated from the transportation phase
and the mixing phase were noted to be insignificant. The spin-
ning stage is the dominant contributor towards most of impact
categories, excepting water depletion. Contributions to the
categories are primarily attributable to the fiber acquisition
stage, which is the cotton cultivation for the virgin cotton
scenario, and the fibers recycling for the recycled cotton
scenario.
3.1.1 Carbon emissions
In fact, land use has effect on the ecosystem. Liu et al. (2010)
have developed a model for calculating the carbon emission
caused by land occupation. For the calculation of land occu-
pation impact, the model withChinese characterization factors
was developed for quantifying the damages to environment by
land use in terms of the change in net primary productivity of
ecosystem. Considering the land type is the semidesert, the
characterization factor of land occupation is 597 g C/m
2
a.
According to the land occupation of per FU cotton, the carbon
emissions caused by land occupation are 3462.6 kg C, and it
transforms 1.14 × 10
4
kg CO
2
based on its molecular weight.
It is noteworthy that the cultivation land can be stored in
soil with the form of soil organic carbon (SOC) because of the
decomposition of humus. The SOC stock changes reflect the
differences between long-term input of litter (above and below
ground) from trees and decomposition of dissolved organic
carbon (Jandl et al. 2006; Miegroet and Olsson 2011).
According to research of Khoshnevisan et al. (2018)and
IPCC guidelines (Tanabe and Wagner 2003), the rough esti-
mation showed that the average C sequestration rate was about
2×10
3
kg C/ha year. Considering the per FU cotton cultiva-
tion, about 0.58 ha of land was needed to satisfy manufac-
turers’feedstock demands. Thus, about 1160 kg C are stock-
ing in the soil and the transformed CO
2
is 3811 kg.
Above all, considering the carbon emissions caused by land
occupation and the carbon storing in soil, the carbon emissions
associated with soil is 6.6 × 10
3
kg CO
2
eq. The carbon emis-
sions associated with yarn manufacturing are 4560 kg CO
2
.
Therefore, the carbon emissions associated with virgin cotton
yarns are 1.1 × 10
4
kg CO
2
eq, when the carbon emissions
caused by land occupation and the carbon storing in soil are
take into account. However, the environmental impacts of
recycled cotton yarns are not affected by agricultural land due
to the use of recycled cotton as raw material, which only emit-
ted4380kgCO
2
eq in its production.
3.1.2 Water use
Considering the irrigation water during cultivation, the water
footprint is introduced for calculating the consumed water of
cotton cultivation. Green water footprint (WF
green
), blue water
footprint (WF
blue
), and grey water footprint (WF
grey
)ofglobal
crop production in a spatially explicit way for the period 1996–
2005 were quantified by Mekonnen and Hoekstra (2011).
Those data are sharing the water footprint website with the form
of database (waterfootprint.org). It shows that WF
green
,WF
blue
,
and WF
grey
of 1000 kg cotton fibers are 1400 m
3
,250m
3
,and
650 m
3
at the national level, respectively. Accordingly, the
water required for per FU melange yarns in cotton cultivation
is 2783 m
3
based on the research of Hoekstra. Considering the
water consumed in production, the water consumption of virgin
cotton fibers is 3514m
3
. According to the calculation of the
LCA, the category of water depletion associated with recycled
cotton yarn manufacturing stages is 583 m
3
. It can be seen that,
for the category of water depletion, the recycled cotton scenario
is superior to the virgin cotton scenario because of the irrigation
water consumption.
3.1.3 Land occupation
The agricultural land occupation is an important factor for
evaluating the category of land use. According to the agri-
cultural land of cotton and annual harvest yield of Xinjiang
province of China in 2017, about per hectare average output
of cotton is 2079.3 kg (National Bureau of Statistics. 2017).
It means that 0.58 ha agricultural land is needed to grow
cotton.
3.2 Main contributors
To evaluate the key processes of the life cycle for the produc-
tion of the yarn in detail, the key processes of the aforemen-
tioned key impact categories of the two scenarios are
Int J Life Cycle Assess

described in Fig. 3. For both scenarios, the electricity
was most significant contributor to the impact on the
main categories. The top three contributors to climate
change were fiber acquisition, electricity, and tap water.
The environmental impacts generated from the waste
discharge are smaller than other processes because
wastewater treatment system is established for reducing
water consumption.
For the virgin cotton yarn scenario, the environmental im-
pact is concentrated in the cotton cultivation and fibers spin-
ning stages. The category of climate change is dominated by
the land occupation. The other categories of environmental
impacts in this stage are dominated by fertilizers and urea
consumption in the cotton cultivation stage. It should be men-
tioned that 79.1% of contribution to the category of water
depletion is attributable to the cotton cultivation, which shows
Fig. 3 Compositions of the key
processes to main categories: A—
virgin cotton yarn scenario, B—
recycled cotton yarn scenario
Table 2 The LCIA results of the
virgin cotton yarn production and
recycled cotton yarn production.
Values are presented per FU
Impact category Unit Virgin cotton Recycled cotton
Climate change kg CO
2
eq 11000 4380
Terrestrial acidification kg SO
2
eq 5.84 5.62
Freshwater eutrophication 10
-3
kg P eq 2.8 19.8
Ozone depletion 10
-8
CFC-11 eq 2.47 4.35
Fossil depletion kg oil eq 1240 1100
Freshwater ecotoxicity kg 1,4-DB eq 0.29 0.45
Human toxicity kg 1,4-DB eq 68.8 69.2
Ionizing radiation kg U235 eq 25.2 75.7
Marine ecotoxicity kg 1,4-DB eq 0.127 0.247
Marine eutrophication kg N eq 2.06 2.04
Metal depletion kg Fe eq 139 44.2
Particulate matter formation kg PM10 eq 1.93 1.82
Photochemical oxidant formation kg NMVOC 5.55 5.42
Terrestrial ecotoxicity kg 1,4-DB eq 0.0358 2.29
Water depletion m
3
3514 583
Land occupation ha 0.58 0
Int J Life Cycle Assess

that the irrigation water, compound fertilizer, and pesticides
are the dominant contributors to the category.
For the recycled cotton yarn scenario, 40.3% of contribu-
tion to the category of water depletion is attributable to the
recycled cotton fiber acquisition, which demonstrated that the
washing process is the dominant contributor to water deple-
tion. Meanwhile, environmental impacts generated from the
washing of fabrics are mitigated effectively by the use of
recycled water.
3.3 Sensitivity analysis
Sensitivity analysis is a way to predict the relationships be-
tween input and output variables in a system (Ye et al. 2017).
Since the production data for yarns may be have uncertainties,
sensitivity analysis was conducted to examine the effects of
changed several production data. In this analysis, 5% of fer-
tilizer consumption is reduced in cotton cultivation stage for
the virgin cotton yarn scenario, 5% of water consumption is
decreased in the washing process for the recycled cotton yarn
scenario, and 5% of total electricity consumption for both
scenarios is decreased. Each parameter was changed indepen-
dently from all others so that the magnitude of its effect on the
base scenarios could be assessed. It should be noted that the
transportation distance is considered a constant in this re-
search, since the environmental impacts generated from the
transportation (less 1% of total environmental impacts) are
small and the contributions of cotton transportation to all im-
pact categories are not sensitive to transportation distance in
the whole life cycle (Zhang et al. 2015).
Fig. 4demonstrates the results of a 5% variation to prom-
inent processes on the aforementioned impact categories.
Obviously, the decreasing of electricity consumption mainly
affects the contribution of the presented stages in the life cycle
of yarns on the aforementioned categories, especially on cli-
mate change and fossil depletion. It indicates that improving
energy efficiency can significantly reduce environmental bur-
dens. Additionally, the decrease in electricity consumption
has a significant influence on human toxicity because of the
combustion of fossil fuels, and water consumption in the
washing process has little effect on human toxicity due to
the use of recycled water. Furthermore, irrigation water and
fertilizer consumption in cotton cultivation stage have a great-
er impact on water depletion.
3.4 Uncertainty analysis
The varying life cycle boundaries, technology levels in differ-
ent countries and regions, lead to the different parameters and
calculation results (Jiao et al. 2019). The LCIA results are
questionable and non-satisfactory for the interpretation phase
without uncertainty analysis in LCA (Bicer and Dincer 2018).
Therefore,aMonteCarlosimulationmethodisusedto
explore the influences of parameter uncertainty distribution
on the aforementioned impact categories.
According to the LCA results, electricity occupies absolute
share in the spinning stage on each category for both scenar-
ios. Fertilizer consumption (includes urea and compound fer-
tilizer) accounts for a critical proportion of water depletion and
climate change in the cotton acquisition stage. The consump-
tion of water for washing is sensitive to the category of water
depletion. The electricity, fertilizer, and water are considered
uncertain parameters due to the change of these parameters
that have strong effects on environmental impacts of two
scenarios.
Determining the distribution of parameters is crucial when
very limited sample data of an uncertain parameter are pro-
vided; the triangular distribution is used (Liu et al. 2012).
Therefore, considering the sample data are finite, it assumed
that these parameters follow the triangular distribution, as
shown in Table 3.
The results show the probability density distribution histo-
grams of water depletion, human toxicity, fossil depletion, and
climate change for both scenarios with a 90% confidence in-
terval (Fig. 5).
Thus, for water depletion, the range of virgin cotton yarns
is from 3489 to 3551 m
3
and the range of recycled cotton
yarns is from 554 to 606 m
3
. For human toxicity, the range
of virgin cotton yarns is from 63.7 to 70.5 kg 1,4-DB eq, and
the range of recycled cotton yarns is from 64.4 to 71.0 kg 1,4-
DB eq. For fossil depletion, the range of virgin cotton yarns is
from 1131 to 1252 kg oil eq and the range of recycled cotton
yarns is from 1033 to 1149 kg oil eq. For climate change, the
range of virgin cotton yarns is from 10643 to 11456 kg CO
2
eq
and the range ofrecycled cotton yarns is from 4078 to 4544 kg
CO
2
eq.
4Discussions
In this paper, the LCA for recycled cotton yarns and virgin
cotton yarns are established to investigate their environmental
impacts. It can provide quantitative value to support the pop-
ularization of recycled cotton and help to reduce the overall
environmental impact in the apparel industry. Fig. 3exhibits
that electricity consumption is the key process in the life cycle
of both the two scenarios. The results show thatenvironmental
impacts of recycled cotton yarns are far less than those of
virgin cotton yarns, except for climate change and water de-
pletion. The reason is that the land occupation and irrigation
water have great impact on environmental impacts of cotton
cultivation. It can be observed that recycled cotton yarn is a
viable alternative to relieve resource and environmental
pressure.
Thus, it can be considered that the recycled fibers can be
effectively avoiding environmental impacts generated from
Int J Life Cycle Assess

the cotton planting. Moreover, the pesticides and fertilizers are
required in cotton cultivation, which is far to be considered
sustainable practice and has deleterious effects on environ-
ment preservation.
From the perspective of manufacturers, compared with en-
vironmental impacts of virgin cotton yarns, the emitted CO
2
eq of the recycled cotton yarns can be decreased by 60.18%.
The consumed Oil eq of the life cycle of the recycled cotton
yarns can be decreased by 11.3%. The consumed water of the
recycled cotton yarns can be saved by 79.1%. There was a
slight increase (0.58%) for human toxicity (shown in Fig. 6). It
reveals that the recycled cotton fibers should be served as a
substitute for virgin cotton fibers.
According to the annual production of reference factory in
2019, recycled cotton fibers account for 3% of annual fibers
and the proportion will be further increased along with the
development of recycled process. There is no degradation in
the recycled cotton products’performance after adding
recycled cotton fibers.
In China, the cotton cultivation area was 3.2 million ha and
the per hectare average output of cotton is 1698.6 kg in 2017.
However, the per hectare output of cotton is 2079.3 kg in
Xinjiang province since its unique geographical location and
climate (National Bureau of Statistics. 2017). It means that the
utilization of 1000 kg recycled cotton yarns can save about
0.5 ha of agricultural land and reduce 6600 kg CO
2
eq. Thus,
agricultural land can be saved by using recycled cotton fibers.
Some feasible improvement opportunities for reducing en-
vironmental impacts of the recycled fibers are put forward.
The energy-saving measures should be adopted for improving
the environmental performance in the production, such as the
relevant know-how about energy efficiency technologies and
practices should be disseminated to textile plants (Hasanbeigi
and Price 2012). A spinning quality control model based on
hierarchical multi-process is used to accurately control yarn
quality, improve the fracture strength, and reduce
nonconforming ratio of yarns (Shao and Ma 2018). Some
measures are adopted for reducing fibers waste percentage,
such as reasonably setting the top card rack density and inser-
tion depth and eliminating embedded fiber in top comb and
cylinder (Xiao et al. 2016).
The government should also strengthen environmental pro-
tection education and raise the awareness of environmental
protection as future works which to enable enterprises to re-
ceive recycled fibers. Most of the old clothes have not been
reprocessed or harmlessly treated yet. It is reported that about
2.6 × 10
10
kg of old clothes is discarded every year. The reuse
rate of old clothes is less than 1%, and the remaining old
clothes are used for incineration and landfill (China
association of circular economy. 2016). For this reason, the
enterprises should further develop related products about
recycled cotton fibers so that it will bring huge potential eco-
nomic benefits.
However, the recovery mode and fiber types have strong
effect on the cost of recycled cotton yarns. Considering the
scattered distribution of recycled cotton fabrics, the diversity
of cotton fabrics, and the complexity of fibers separation, the
cost of recycled cotton yarns may be higher than that of virgin
cotton yarns, and an important trend in future work is how to
reduce the costs of recycling cotton yarns.
The morphology and physical properties of cotton fibers
are crucial to evaluate the mechanical properties of yarns
(Memon et al. 2015). Compared with the dyed fibers, the
dyestuffs and auxiliaries are not necessary to achieve good
Fig. 4 Sensitivity analysis results
Table 3 Uncertain parameters of
distributions Input parameters Type Distribution parameters Mean value Standard deviation Unit
Fertilizer Triangular 483.4, 605.0, 665.3 584.5 38.1 kg/t
Electricity-virgin Triangular 3543.4, 3991.0, 4223.1 3919.8 141.9 kWh/t
Washing water Triangular 20.0, 22.2, 24.4 22.2 0.9 m
3
/t
Electricity-recycled Triangular 3756.8, 4148.0, 4427.7 4111.3 138.2 kWh/t
Land occupation Triangular 5626,5800 5974 5800 56 m
2
/t
Int J Life Cycle Assess

colorfastness of the virgin cotton fibers and recycled cotton
fibers. Moreover, the mechanical properties of recycled cotton
yarns are weaker than virgin cotton yarns because of the sec-
ond use of the recycled cotton fibers. Generally, the recycled
cotton fibers are fully mixed with other type fibers spun to
yarns in a certain proportion and woven into fabrics. The
virgin cotton fibers are always mixed with other type fibers
spun into yarns when the color scheme of yarns is taken into
consideration.
Since the downstream data of recycled cotton fibers are
difficult to collect, we tried our best to collect extensive data
to quantify the cradle-to-gate life cycle impacts of yarns.
There are still some limitations in this study and listed as
follows:
&The cotton cultivation stage is simplified since it is com-
plex and long-time.
&One factory production data is collected from the annual
production data of melange yarn manufacturer in Zhejiang
province in China, and the uncertainties caused by geo-
graphical differences are existing and need to be further
investigated.
&There are many recycling methods for the recycled cotton
fibers which have different environmental impacts.
Fig. 5 Probability density of water depletion, human toxicity, fossil depletion, and climate change
Int J Life Cycle Assess

&The differences in production technologies between China
and Europe may bring uncertainties such as fertilizers and
pesticides based on European situations.
&The noise generated in the production plants is ignored
and this deserves to be further studied.
5 Conclusions
In this work, a cradle-to-gate LCA of virgin cotton yarns and
recycled cotton yarns has performed using on-site investiga-
tion data. The LCIA results reveal that environmental impacts
of recycled cotton yarns are far less than those of virgin cotton
yarns. Notable impacts on climate change, fossil depletion,
water depletion, and human toxicity have been observed. In
cotton cultivation, the land occupation and irrigation water
have great impact on environmental impacts of cotton culti-
vation. In spinning, the electricity is the key process for the
environmental impacts in the virgin cotton yarn scenario; ac-
cordingly, the electricity and water consumption are the key
processes in the recycled cotton yarn scenario. About 0.5 ha of
agricultural land can be saved, 6600 kg CO
2
eq can be re-
duced, and 2783 m
3
irrigation water can be saved by using
1000 kg of the recycled cotton yarns.
Sensitivity analysis indicates that reducing energy con-
sumption and improving water efficiency are significant to
reduce the overall environmental burdens. Uncertainty analy-
sis determines the probability density distribution of water
depletion, human toxicity, fossil depletion, and climate
change for both scenarios with a 90% confidence interval.
That reveals recycled cotton yarn is a viable alternative to
relieve resource and environmental pressure.
Furthermore, the pesticides and fertilizer are required in the
cotton cultivation, which is far to be considered sustainable
practice and has deleterious effects on environment preserva-
tion. Recycled cotton fibers can serve as a substitute for virgin
cotton fibers to avoid environmental impacts generated from
the cotton planting and reduce agricultural land occupation.
More methods on recycling cotton fibers should be further
developed to achieve the reuse of waste resources.
Funding information This research was financially supported by the
National Natural Science Foundation of China (Grant no. 51722502).
Compliance with ethical standards
All the listed authors have confirmed the final version of the manuscript
and approved it for submission.
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