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industrial crops and products 27 (2008) 1–10
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/indcrop
The environmental impacts of the production of hemp and
flax textile yarn
Hayo M.G. van der Werf∗, Lea Turunen
INRA, Agrocampus Rennes, UMR 1069, Sols, Agronomie, Spatialisation, 65 rue de Saint Brieuc CS 84215, 35042 Rennes Cedex, France
article info
Article history:
Received 5 January 2007
Received in revised form
26 April 2007
Accepted 20 May 2007
Keywords:
Environmental impact
Fibre processing
Flax
Hemp
Yarn production
abstract
This study aimed to quantify major environmental impacts associated with the production
of hemp yarn using Life Cycle Analysis (LCA). A reference scenario of traditional hemp warm
water retting was compared to: (1) bio-retting, i.e. hemp green scutching followed by water
retting, (2) babyhemp, based on stand retting of pre-mature hemp, (3) dew retting of flax.
Overall, neither of the alternative scenarios was unambiguously better than the reference.
The impacts of the hemp reference scenario and the flax scenario were similar, except
for pesticide use (higher for flax) and water use during processing (higher for hemp). Bio-
retting had higher impacts than the reference scenario for climate change and energy use,
due to higher energy input in fibre processing. Babyhemp had higher impacts than the
reference scenario for eutrophication, land occupation and pesticide use. A reduction of the
environmental impacts of hemp yarn should give priority to reduction of energy use in the
fibre processing and yarn production stages and to reduction of eutrophication in the crop
production phase.
© 2007 Elsevier B.V. All rights reserved.
1. Introduction
Ever since Eve ate the apple, clothing and textiles in general
have been indispensable parts of our human existence. These
days, textile manufacture and retail are a big business, as the
lifetime of a product is determined not so much by its weara-
bility than by ever changing fashion trends.
Cotton and synthetic fibres meet most of the world’s textile
demand (WWF, 1999). Both are associated with major envi-
ronmental problems: synthetic fibres deplete fossil energy
resources, while contemporary cotton cultivation is charac-
terised by high water requirements and use of substantial
amounts of fertilisers and pesticides (WWF, 1999). There is an
increasing recognition that a shift towards non-cotton natural
fibres could contribute greatly to the sustainability of the tex-
tile industry. In the European context, alternative fibre crops
such as hemp and flax are interesting, because they grow well
∗Corresponding author.
E-mail address: Hayo.vanderWerf@rennes.inra.fr (H.M.G. van der Werf).
Europe wide, while cotton thrives only on the most southern
edge of the continent. Furthermore, fibre crop cultivation is
compatible with the recent European Union (EU) agricultural
policy promoting a switch from food to non-food crops.
In November 2002, a comprehensive EU-funded 3-year
study called HEMP-SYS was started (Amaducci, 2003). This
project has the aim of promoting the development of a
competitive, innovative and sustainable hemp fibre textile
industry in the EU, by developing an improved, ecologically
sustainable production chain, for high quality hemp fibre tex-
tiles, coupled to an integrated quality system for stems, raw
and processed fibres, yarns and fabrics based on eco-labelling
criteria. Within the framework of the project, the present study
aims to quantify major impacts associated with the produc-
tion of hemp yarn for textile using Life Cycle Analysis (LCA),
to generate propositions for modifications of the production
chain, leading to reduced environmental impacts.
0926-6690/$ – see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.indcrop.2007.05.003
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2industrial crops and products 27 (2008) 1–10
No studies using LCA to assess the environmental impacts
of the production of hemp yarn or of yarn from other bast
fibre crops (e.g. flax, jute) were found in the scientific litera-
ture. Detailed results concerning the environmental impacts
of hemp field production in comparison to those of a range of
other crops were published (van der Werf, 2004).
2. Materials and methods
2.1. Evaluation methodology
Environmental impacts associated with the production of yarn
from hemp and flax were evaluated using Life Cycle Assess-
ment (LCA), as detailed in Turunen and van der Werf (2006).
LCA is a method to assess impacts associated with a product,
by quantifying and evaluating the resources consumed and
the emissions to the environment at all stages of the prod-
uct’s life cycle—from the extraction of resources, through the
production of materials, product parts and the product itself,
and the use of the product, to its reuse, recycling or final dis-
posal (Guin´
ee et al., 2002). In the Inventory Analysis phase,
inputs from the environment (resources used) and outputs to
the environment (emissions) associated with the product are
listed. In the Impact Assessment phase, inputs and outputs
are interpreted in terms of environmental impacts (Guin´
ee et
al., 2002).
2.2. Goal and scope of the study
The study aims to quantify major impacts associated with
three scenarios for the production of hemp textile yarn,
in order to establish reference data for environmental per-
formance, and identify problem areas and potential for
improvement. We evaluated a flax yarn production scenario
for bench-marking, as the flax textile industry uses technolo-
gies similar or identical to those used for hemp, while being
economically much more important than the hemp textile
industry.
Impacts are expressed per 100kg of yarn of a metric count
number (Nm) of 26 (a g of 26 Nm yarn is 26 m long). The present
study compares four scenarios for the production of bleached
textile yarn: hemp water retting (HW), hemp bio-retting (HB),
babyhemp (BH) and flax dew retting (FD). Each of these sce-
narios consists of three production stages: crop production,
production of long fibre, and yarn production. For each of
these stages the analysis includes the use of major inputs
(machines, energy carriers, chemicals, water), buildings are
not included in the analysis.
2.3. Yarn production scenarios
For HW and HB crop production is according to a generic
Central-European scenario, mainly based on data from Hun-
gary (Iv´
anyi, personal communication, 2004), with harvest at
the end of the flowering stage of the crop. For BH crop produc-
tion is in Italy, according to Amaducci (2005), and for FD crop
production is based on data from France, Belgium and The
Netherlands. None of the crop scenarios involves irrigation.
Inputs used in crop production are presented in Table 1.
Table 1 – Inputs used (in kg/ha) for field production of
Central European hemp, Baby hemp and flax
Hemp central
Europe
Baby
hemp
Flax
N (ammonium nitrate) 68 28 40
P2O5(triple superphosphate) 30 12 30
K2O (potassium chloride) 114 46 60
CaO 333 135 333
Seed for sowing 55 100 115
Pesticide (active ingredient) 0 4.0 2.6
Diesel 55 54 57
Agricultural machinery 17.3 15.0 15.5
For HW production of long fibre is based on traditional
warm water retting according to current production practices
in Hungary (Homonyik, personal communication, 2004). The
crop is mown and bound in sheaves, which dry on the field.
Dry sheaves are retted in open concrete retting pools, using a
28 ◦C mix of warm thermal water and cold well water. After ret-
ting sheaves are air-dried, dried sheaves are stored outdoors,
causing a 10% loss due to spoiling. Stems are scutched using
a hemp scutching machine to obtain separation into scutched
long fibre, scutched short fibre and shives.
HB corresponds to an experimental process developed
by Gruppo Fibranova in Italy within the HEMP-SYS project
(Tofani, personal communication, 2004). The crop is mown,
cut into 1 m sections, laid into a parallel swath to dry on the
field and baled using a round bale press; bales are stored
indoors. Stem sections are green scutched (i.e. before ret-
ting), using a flax scutching machine to obtain separation
into green scutched long fibre, green scutched short fibre and
shives. Green scutched long fibre is retted in open tanks filled
with warm (35 ◦C) water, inoculated with selected bacteria to
improve retting. The water is heated using wood pellets. After
retting the fibre is rinsed, and dried using natural gas. The
dried fibre is softened using fluted rollers to obtain long fibre
for processing into yarn.
BH crop growth is terminated by herbicide spraying when
the crop is 120–140 cm tall. The crop is left standing in the
field to ret for 30–50 days, harvested (“pulled”) using flax har-
vesters, laid in a parallel swath to dry, turned once and baled
with a round bale press. Bales are stored indoors. Stems are
scutched using a flax scutching machine to obtain separation
into scutched long fibre, scutched short fibre and shives.
FD is harvested (“pulled”) using flax harvesters, laid in a
parallel swath to dry, turned twice and baled with a round bale
press. Bales are stored indoors. Stems are scutched using a flax
scutching machine to obtain separation into seed, scutched
long fibre, scutched short fibre and shives.
The yarn production stage is identical for the four scenarios
and consists of the following processes: hackling to produce
sliver, production of rove, bleaching, wet ring spinning and
winding.
Crop yield levels and amounts produced for intermediate
and final products for the four scenarios are given in Table 2.
These data are based on a range of sources: statistical data,
literature references, industry data and expert opinion, as
detailed in Turunen and van der Werf (2006).
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industrial crops and products 27 (2008) 1–10 3
Table2–Yields per ha of the intermediate and final products for the four scenarios
Products Hemp FD (flax dew retting)
HW (water retting) HB (bio-retting) BH (babyhemp)
Green stem 8000 8000 6000
Retted stem 6480 3250 5400
Green scutched long fibre 1000
Green scutched short fibre 1000
Grain yield (9% humidity) 0 0 0 600
Green scutched long fibre after retting 658
Scutched long fibre 583 293 972
Scutched short fibre 1490 748 594
Shives 2592 3600 1300 2970
Yarn 236 213 119 512
Yields are in kg/ha of dry material at 14% humidity.
2.4. Inventory assessment
Our partners in the HEMP-SYS project provided data on
resource use and emissions for many of the major processes
making up the three production stages considered in this
study. Data for energy carriers and for transport are from the
BUWAL 250 database (BUWAL, 1996). For electricity the Euro-
pean UCPTE energy mix data from the BUWAL database are
used. Values for resource use and emissions of other processes
are based on literature references and several LCA databases.
Details are in Turunen and van der Werf (2006).
A number of processes studied yield more than one prod-
uct, e.g. scutching produces long fibre, short fibre and shives.
In such a case the impacts resulting from the process have
to be allocated (i.e. partitioned among) the products. We
allocated impacts according to the economic value of the
products, which presents a measure of the incentive for pro-
duction. Economic allocation is not without problems, as the
prices of natural fibres fluctuate, but was chosen over mass-
based allocation, because long (and short) fibres represent only
a small fraction of the stem mass, but they are the major rea-
son for hemp cultivation.
2.5. Impact analysis
In the Impact Assessment phase, it is first determined
which impact categories will be considered. In this study we
consider: eutrophication, climate change, acidification, non-
renewable energy use and land occupation, this set of impact
categories is appropriate for the evaluation of agricultural
products. Next, the indicator result for each impact cate-
gory is determined by multiplying the aggregated resources
used and the aggregated emissions of each individual sub-
stance with a characterisation factor for each impact category
to which it may potentially contribute. Characterisation fac-
tors are substance-specific, quantitative representations of
the additional environmental pressure per unit emission of
a substance. The characterisation factors used in this study
are given below for each impact category.
Eutrophication covers all potential impacts of high levels
of macronutrients in the environment, in particular of N and
P. As recommended by Guin ´
ee et al. (2002), eutrophication
potential (EP) was calculated using the generic EP factors in
kg PO4-equivalents, NH3: 0.35, NO3: 0.1, NO2: 0.13, NOx: 0.13,
PO4:1.
Climate change is defined here as the impact of emissions
on the heat radiation absorption of the atmosphere. As rec-
ommended by Guin´
ee et al. (2002), Global Warming Potential
for a 100 year time horizon (GWP100) was calculated according
to the GWP100 factors by IPCC in kg CO2-equivalents, CO2:1,
N2O: 310, CH4: 21.
Acidifying pollutants have a wide variety of impacts on soil,
groundwater, surface waters, biological organisms, ecosys-
tems and materials (buildings). As recommended by Guin´
ee
et al. (2002), acidification potential (AP) was calculated using
the average European AP factors in kg SO2-equivalents, NH3:
1.6, NO2: 0.5, NOx: 0.5, SO2: 1.2.
Non-renewable energy use refers to the depletion of ener-
getic resources. Energy use was calculated using the Lower
Heating Values proposed in the SimaPro 1.1 method (PR´
e
Consultants, 1997), crude oil: 42.6 MJ/kg, natural gas: 35 MJ/m3,
uranium: 451,000 MJ/kg, coal: 18 MJ/kg, lignite: 8 MJ/kg, gas
from oil production 40.9 MJ/m3.
Land occupation refers to the loss of land as a resource, in
the sense of being temporarily unavailable for other purposes
due to the growing of crops. This is a quantitative assessment,
which does not distinguish quality of land use.
In addition to these impact categories, the amount of pesti-
cide active substance used as well as water used in processing
is assessed. Thus water used by the crop (transpiration loss)
during the crop production and water used for pesticide appli-
cation is not included in the assessment.
3. Results
3.1. Eutrophication
Eutrophication per 100 kg of yarn was lowest for FD (2.6kg
PO4-eq.), followed by HB and HW (3.0), and highest for BH
(4.9) (Table 3). The contribution of the crop production stage
to eutrophication ranged 75–93%, depending on the scenario
(Fig. 1). Emissions from the soil (N and P) made up about 90% of
this. The remainder resulted, e.g. from the diesel combustion
in the field operations. The retting effluent contributed 13%
of eutrophication in HW (Fig. 1). The contribution of effluents
in HB was minimal. Yarn production contributed to eutroph-
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4industrial crops and products 27 (2008) 1–10
Table3–Theenvironmental impacts of yarn production
expressed per 100 kg of yarn for the investigated
scenarios: hemp water retting (HW), hemp bio-retting
(HB), babyhemp (BH) and flax dew retting (FD)
Impact category Hemp FD
HW HB BH
Eutrophication (kg PO4-eq.) 3.04 3.02 4.94 2.61
Climate change (kg CO2-eq.) 1350 1810 1460 1360
Acidification (kg SO2-eq.) 7.38 9.01 8.02 8.16
Non-renewable energy use (MJ) 25,500 35,800 26,500 26,100
Land occupation (m2year) 1160 1260 2410 1150
Pesticide use (act. subst.) (kg) 0 0 0.874 0.296
Water use (m3) 19.9 22.1 7.63 7.23
ication through emissions due to electricity production. The
relative contribution of the production of 100kg of yarn to per
capita eutrophication in Europe was 6.8–12.9%, depending on
the scenario (Table 4).
3.2. Climate change
Climate change per 100 kg of yarn was lowest for HW and FD
(1350 and 1360 kg CO2-eq., respectively), followed by BH (1460),
HB had the highest value (1810) (Table 3). For FD, HW and BH,
the crop production stage represented 15–24% of the impact,
fibre processing 6–7% and yarn production 69–78% (Fig. 2). For
HB fibre processing made up 28% of the total impact, which
reduced the relative contribution of yarn production to 56%.
The large contribution of the fibre processing stage in this sce-
nario was due to fibre drying. The relative contribution of the
production of 100 kg of yarn to per capita climate change in
Europe ranged from 9.2 to 12.4% (Table 4).
3.3. Acidification
Acidification per 100 kg of yarn was lowest for HW (7.4kg SO2-
eq.), followed closely by BH (8.0) and FD (8.2). It was highest
for HB (9.0) (Table 3). Acidification was largely (62–79%) due
to yarn production in all scenarios (Fig. 3). Fibre processing
was responsible for 8.5–9.7% of the impact in all scenarios
except HB. Drying increased the contribution of fibre process-
ing to 24% in this case. The contribution of crop production
was highest for BH (19%) and lowest for FD (10%). The relative
contribution of the production of 100 kg of yarn to per capita
acidification in Europe was 8.8–10.7% (Table 4).
3.4. Non-renewable energy use
Non-renewable energy use per 100 kg of yarn washighest in HB
(35,800 MJ) and similar for the other three scenarios (around
26,000 MJ) (Table 3). Energy use resulted mainly from yarn pro-
duction: 85–88% in all scenarios, except for HB, where it was
63% (Fig. 4). The yarn production stage was less important in
Fig. 1 – Contribution (in kg PO4-eq.) of the different stages of the production of 100kg of yarn to eutrophication, according to
the scenarios: hemp water retting (HW), hemp bio-retting (HB), babyhemp (BH) and flax dew retting (FD). Unit processes
within stages are shown separately if they contribute 10% or more to the total impact for one or several of the scenarios.
“Others” refers, for the specific production stage, to the impacts from unit processes, other than those mentioned separately.
Table 4 – Normalised impacts, i.e. the contribution of the production of 100 kg of yarn according to the investigated
scenarios (hemp water retting (HW), hemp bio-retting (HB), babyhemp (BH) and flax dew retting (FD)) to per capita
environmental impacts in Western Europe
Impact category Normalisation value Reference for
normalisation value
Contribution (%)
HW HB BH FD
Eutrophication (kg PO4-eq.) 38.4 Huijbregts et al. (2001) 7.9 7.9 12.9 6.8
Climate change (kg CO2-eq.) 14,600 Huijbregts et al. (2001) 9.2 12.4 10.0 9.3
Acidification (kg SO2-eq.) 84.2 Huijbregts et al. (2001) 8.8 10.7 9.5 9.7
Non-renewable energy use (MJ) 154,000 PR´
e Consultants (1997) 16.6 23.2 17.2 16.9
Land occupation (m2year) 10,100 Huijbregts et al. (2001) 11.5 12.5 23.9 11.4
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industrial crops and products 27 (2008) 1–10 5
Fig. 2 – Contribution (in kg CO2-eq.) of different stages of the production of 100kg of yarn to climate change, according to the
scenarios: hemp water retting (HW), hemp bio-retting (HB), babyhemp (BH) and flax dew retting (FD). Unit processes within
stages are shown separately if they contribute 10% or more to the total impact for one or several of the scenarios. “Others”
refers, for the specific production stage, to the impacts from unit processes, other than those mentioned separately.
HB due to higher energy use in fibre processing (33% of total),
largely due to drying. In the other scenarios the contribution
of fibre processing was 6–7%, while in all scenarios energy use
in crop production contributed only 4–8%.
The yarn production stage, which contributed, by far, most
to energy use (as well to climate change and acidification), was
essentially the same for the four scenarios. Its large contribu-
tion overshadowed the differences in the previous stages of
the production chain. Fig. 5, where the impacts of the yarn
production stage were excluded, allows a better examination
of the significance of the various other sub-processes. Apart
from fibre drying, the retting in tanks (essentially the heating
of retting water) increases the energy use in the bio-retting
scenario. The effect of softening is negligible.
In all scenarios the 400-km transport of long fibre from the
fibre processing to the yarn-processing site contributed very
little to energy use in comparison with the other processes.
The relative contribution of the production of 100kg of yarn
to per capita energy use in Europe ranged from 16.6 to 23.2%
(Table 4).
Fig. 3 – Contribution (in kg SO2-eq.) of different stages of the production of 100kg of yarn to acidification, according to the
scenarios: hemp water retting (HW), hemp bio-retting (HB), babyhemp (BH) and flax dew retting (FD). Unit processes within
stages are shown separately if they contribute 10% or more to the total impact for one or several of the scenarios. “Others”
refers, for the specific production stage, to impacts from unit processes, other than those mentioned separately.
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6industrial crops and products 27 (2008) 1–10
Fig. 4 – Contribution (in MJ) of different stages of the production of 100kg of yarn to non-renewable energy use, according to
the scenarios: hemp water retting (HW), hemp bio-retting (HB), babyhemp (BH) and flax dew retting (FD). Unit processes
within stages are shown separately if they contribute 10% or more to the total impact for one or several of the scenarios.
“Others” refers, for the specific production stage, to the impacts from unit processes, other than those mentioned separately.
3.5. Land occupation, pesticide use, water use
FD and HW had the smallest land occupation per 100 kg of
yarn (1150 and 1160 m2year, respectively), followed closely by
HB (1260) (Table 3). Land occupation for BH was more than
double (2410). The relative contribution of the production of
100 kg of yarn to per capita land occupation in Europe ranged
from 11.4 to 23.9% (Table 4).
Pesticide use was zero for HW and HB, 0.296kg of pesticide
active substance were used in FD and 0.874kg in BH (Table 3).
Expressed per hectare, this corresponded to 2.58kg for FD and
4 kg for BH.
Water use was similar for FD and BH (7.2 and 7.6m3, respec-
tively), and for HW and HB (19.1 and 22.1m3, respectively)
(Table 3). Rove bleaching accounted for all of water use in BH
and FD. In HW and HB rove bleaching used the same volume
(i.e. 7.6 m3), while the rest was consumed in retting. In HB,
water use was 36% for retting and 64% for rinsing.
3.6. Scenario variations
The sensitivity of the results of HW, HB and FD to changes in
some key parameters was explored by comparing variations of
these scenarios to their respective original scenarios. For HW
Fig. 5 – Contribution (in MJ) of unit processes of the crop production and fibre processing stages of the production of 100 kg
of yarn to non-renewable energy use, according to the scenarios: hemp water retting (HW), hemp bio-retting (HB),
babyhemp (BH) and flax dew retting (FD).
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industrial crops and products 27 (2008) 1–10 7
Table5–Impacts for the hemp water-retting scenario and its variants per 100 kg yarn: the effect of crop yield, nitrate
leaching and use of gas for heating retting water
Eutrophication
(kg PO4-eq.)
Climate change
(kg CO2-eq.)
Acidification
(kg SO2-eq.)
Non-ren. energy
use (MJ)
Land occupation
(m2year)
HW, hemp water retting 3.04 1350 7.38 25,500 1160
HW1, crop yield + 25% 2.58 (−15.1%) 1300 (−3.7%) 7.18 (−2.7%) 5,200 (−1.2%) 927 (−20.1%)
HW2, crop yield −25% 3.80 (+25.0%) 1440 (+6.7%) 7.72 (+4.6%) 25,900 (+1.6%) 1540 (+32.8%)
HW3, NO3emissions −50% 2.07 (−31.9%) 1330 (−1.5%) = = =
HW4 + gas heating 3.07 (+1.0%) 1620 (+20.0%) 7.73 (+4.7%) 30,100 (+18.0%) =
Pesticide use and water use are not shown, as the scenario alterations did not affect them. Symbol “=” means that the value is equal to that of
the reference scenario.
Table6–Impacts for the hemp bio-retting scenario and its variants per 100 kg yarn: the effect of using gas instead of
wood for water heating, energy use for drying, and using wood instead of gas for fibre drying
Eutrophication
(kg PO4-eq.)
Climate change
(kg CO2-eq.)
Acidification
(kg SO2-eq.)
Non-ren. energy
use (MJ)
Land occupation
(m2year)
HB, hemp bio-retting 3.02 1810 9.01 35,800 1260
HB1, gas instead of wood
for water heating
2.99 (−1.0%) 1920 (+6.1%) 8.94 (−0.8%) = =
HB2, no energy for drying 2.95 (−2.3%) 1400 (−22.7%) 7.91 (−12.2%) 28,000 (−21.5%) =
HB3 = HB1 + HB2 2.92 (−3.3%) 1520 (−16.0%) 7.85 (−12.9%) 28,100 (−21.5%) =
HB4, wood instead of gas
for fibre drying
3.10 (+2.6%) 1510 (−16.6%) 9.18 (+1.9%) 35,600 (−0.6%) =
Pesticide use and water use are not shown, as the scenario alterations had no effect on them. Symbol “=” means that the value is equal to that
of the reference scenario.
a 25% change in the assumed crop yield of 8 tonnes/ha had a
major effect on eutrophication and land occupation, while the
effect on other impact categories was small (HW1 and HW2,
Table 5). The effect of decreasing the nitrate field emissions by
50% was investigated, as in certain pedo-climatic conditions
(e.g. in Hungary) nitrate leaching is significantly lower than the
assumed 40 kg/ha of nitrogen, which is based on the French
climate and soil conditions. Eutrophication is observed to be
very sensitive to nitrate emissions, whereas the other impacts
are barely affected (HW3). The last modification to the refer-
ence scenario concerns the use of fossil energy for heating
the retting water, since hot thermal water is not available in
most places. This would cause a major increase in both cli-
mate change (+20%) and energy use (+18%), but would hardly
affect eutrophication or acidification (HW4).
For HB some modifications to fibre processing were
explored, in order to evaluate possibilities for improving its
environmental profile. First, the substitution of the renewable
energy source (wood pellets) by natural gas for heating the ret-
ting water caused a modest increase of climate change (HB1,
Table 6). This is mainly caused by the fact that the non-fossil
CO2emissions resulting from the use of wood pellets do not
contribute to climate change, whereas the fossil CO2resulting
from natural gas does. If no energy was used in fibre drying,
energy use and climate change would be reduced by over 20%,
i.e. drying accounts for 20% of these impacts over the yarn
production chain (HB2). Effect on acidification is less. A combi-
nation of the two previous modifications would yield impacts
similar to those of the no-energy variant (HB3). Substitution
of gas by a renewable energy source in fibre drying would sig-
nificantly reduce climate change, but would hardly affect the
other impacts (HB4).
Economic allocation of impacts is often debated on the
grounds that market prices fluctuate and thus introduce
uncertainty. The effect of different prices for scutching co-
products was tested for FD, as the relative prices of flax
co-products differed significantly from those of hemp. If flax
co-products had the same prices as hemp co-products, all
Table7–Impacts for the flax dew-retting scenario and its variants per 100 kg yarn
Eutrophication
(kg PO4-eq.)
Climate change
(kg CO2-eq.)
Acidification
(kg SO2-eq.)
Energy use
(MJ)
Land occupation
(m2year)
Pesticide use
(kg act. subst.)
FD Flax dew retting 2.61 1360 8.16 26100 1150 0.296
FD1 Hemp prices at scutching 1.99 (−24%) 1280 (−6%) 7.72 (−5%) 25300 (−3%) 833 (−28%) 0.215 (−27%)
FD2 Hemp prices at scutching,
except shives
2.36 (−10%) 1330 (−2%) 7.99 (−2%) 25800 (−1%) 1020 (−11%) 0.263 (−11%)
Water use is not shown, as the scenario alterations did not affect it. Prices (per kg) used in the flax scenario and resulting allocation factors:
long fibre D1.80 (86.8%), short fibre D0.35 (10.3%), shives D0.02 (3.0%). FD1 prices and allocation factors: long fibre D1.75 (62.1%), short fibre
D0.75 (16.2%), shives D0.20 (21.7%). FD2 prices and allocation factors: long fibre D1.75 (77.1%), short fibre D0.75 (20.2%), shives D0.02 (2.7%).
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8industrial crops and products 27 (2008) 1–10
impacts of the flax scenario would decrease (FD1, Table 7). The
effect was major on eutrophication, land occupation and pes-
ticide use, whereas climate change, acidification and energy
use were affected only modestly. If flax long and short fibre
(but not flax shives) had the same prices as the correspond-
ing hemp co-products, then the impacts of the flax scenario
would decrease but to a lesser extent (FD2).
4. Discussion
4.1. Hemp bio-retting relative to hemp warm water
retting
HB had higher impacts than HW for all impacts except
eutrophication and pesticide use. The higher impacts for cli-
mate change and acidification are related to the higher energy
use in fibre processing, which, in turn, is mainly due to the
retting process. HB involves heating the retting water and dry-
ing of the retted fibre, whereas in HW naturally warm water
is used and stems dry on the field. For climate change, the
scenarios differed due to the fibre drying process only. Heat-
ing of retting water did not contribute to this impact, due to
the renewable energy source (wood chips) used. Had a non-
renewable source (e.g. gas), been used, the climate change
impact would have further increased by 6%.
The yield percentages of long fibre were slightly lower in HB
than in HW: the yarn yield in HB was 90% of that of HW. As a
consequence, even with identical inputs, impacts (expressed
in terms of the final product, yarn) would be higher for HB.
This is illustrated by the results in the land occupation cate-
gory, in which HB has a slightly higher impact, although the
crop production stage, which is the only contributor to land
occupation, was identical for the two scenarios.
Crop production, in particular nitrate leaching, was the
main contributor to eutrophication. Identical results in this
category for the two scenarios are a consequence of the shared
crop production stage. The above-mentioned effect of differ-
ences in yield is counterbalanced by the somewhat higher
emissions due to the retting liquor in HW.
The slightly higher water use in HB goes against one of
the main goals of this method: to reduce water consump-
tion by green decorticating the stems, thus minimising the
bulk of retted material. However, the rinsing step in this sce-
nario increased water consumption. Without rinsing, water
use would come down to 13m3/100 kg of yarn, which is signif-
icantly less than the 20 m3of HW.
4.2. Babyhemp relative to hemp warm water retting
BH had higher values than HW for all impacts except water
use, due to its lower yield: 3.25 tonnes/ha of retted stem versus
6.5 tonnes/ha for HW. For BH herbicide use was 0.9kg of active
substance per 100 kg of yarn, for HW no herbicide was used.
For BH water use was 38% of that of HW, since no water was
used in retting, but only in bleaching.
4.3. Hemp bio-retting relative to babyhemp
HB had higher values for energy use, climate change, acidi-
fication and water use. The main reason is its more energy
intensive fibre processing stage. BH had higher impacts for
eutrophication and land occupation, due to its lower yield.
Pesticide use was also higher for BH.
4.4. Flax dew retting relative to hemp warm water
retting
FD was similar to HW for all impacts except eutrophication,
water use and pesticide use. Eutrophication was slightly lower,
because FD does not involve effluents. FD water use was lower,
as water was used only in rove bleaching. Pesticide use for
FD (0.296 kg) was higher than for HW (0 kg). FD yarn yield
per hectare was double compared to that of HW. This was
surprising, since higher yield is often given as one of the
major advantages of hemp over flax. However, scutching of
HW yields a long to short fibre ratio of 28–72%, whereas for
scutching of FD this ratio is 62–38%. This higher long fibre
extraction rate largely compensated the 25% lower green stem
yield of flax.
The flax yield of 6 tonnes/ha used in this study can be
debated, but so can the hemp yield of 8 tonnes/ha. Of the many
yield levels found in the literature, we tried to find realistic
comparable values for the two crops. For hemp, the sensitiv-
ity analysis of the results to yield level revealed that impacts
dominated by the crop production stage, such as eutrophica-
tion and land occupation, were almost proportionally affected
by changes in per ha yield. Other impact categories were less
sensitive to changes in yield.
The scenario variations concerning prices of flax scutch-
ing co-products illustrate that at current prices economic
returns are largely generated by the flax long fibre and, as
a result, the environmental impacts are allocated mostly
to it. For hemp, economic value of the co-products and,
consequently, the environmental impacts are more evenly dis-
tributed. The hemp prices applied to flax allocated a greater
share of the impacts to the other co-products and decreased
the impacts for flax long fibre. The scutching price alteration
affected mainly the impacts dominated by the crop produc-
tion stage, i.e. eutrophication, land occupation and pesticide
use, because the impacts caused by post-scutching processes
are not affected by this allocation.
5. Environmental “hot spots” of the hemp
scenarios
5.1. In general
A normalisation of the results indicates the areas that need
most attention. The normalisation revealed that the produc-
tion of hemp and flax yarn contributed more to energy use
than to other impacts. Energy use, in turn, was dominated by
yarn production, mainly due to electricity. The impacts energy
use, climate change and acidification are strongly interrelated,
as energy demand is largely met byfossil fuels, the combustion
of which results in the emissions of carbon dioxide and sul-
phur oxides. The former is the most well known greenhouse
gas, while the latter contributes to acidification. Consequently,
yarn production contributes most to climate change and acid-
ification. For the four scenarios, total energy consumption of
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industrial crops and products 27 (2008) 1–10 9
yarn production is three times higher than comparable litera-
ture values for cotton spinning (Turunen and van der Werf,
2006). This seems to result mainly from differences in the
cotton and bast fibre spinning technology.
For eutrophication, the crop production phase was the
biggest contributor. The eutrophying emissions resulting from
hemp and flax growing are, however, by no means exceptional.
In fact, hemp has been identified as a low-impact crop relative
to other annual crops (van der Werf, 2004). Some emissions
via leaching from agricultural land seem inevitable. But to
minimise the impact, any measures leading to a reduction in
nitrate leaching are highly interesting, as a 50% reduction of
the amount of NO3leached reduced eutrophication by 32%
over the yarn production chain. For the crop production phase
alone, a reduction of eutrophication of 43% was reported (van
der Werf, 2004). In general, the optimisation of nitrogen fertil-
isation and the reduction of the period between harvest and
the establishment of the next (catch) crop are the principal
measures recommended to reduce NO3leaching (Gustafson
et al., 2000). However, fertilisation was optimised in our sce-
narios, therefore a rapid establishment of the next crop or of
a catch crop seems the most promising measure to reduce
nitrate emissions and eutrophication.
5.2. Hemp warm water retting
In the literature, water retting is often considered to be “bad”
for the environment, due to the emissions from the retting
water effluent. However, in this study the contribution of the
retting liquor (after wastewater treatment) to eutrophication
was small compared to the impact of the crop production
stage. The situation would obviously be different without a
wastewater treatment process. It should be also remembered
that LCA is a global analysis and while globally the emissions
of eutrophying substances from retting may not be significant,
they might, however, have a considerable local impact at the
recipient water body.
This scenario included the availability of free thermal
water, which is not generally the case. If retting water were
heated by gas, energy use and climate change would increase
by around 20%, so the availability of thermal water is a real
advantage. The effect of 400km transport (of long fibre) had a
negligible impact on energy use. Thus, from the environmen-
tal point of view, even fairly long transport distances may be
justified, if “free” warm water can be exploited. Economical
constraints might of course be different. Thermal water is not
available in many places, but waste heat of process cooling
waters might be available.
5.3. Bio-retting
High energy input in the fibre processing stage is the most crit-
ical issue of the bio-retting scenario. Especially drying of the
fibre after retting stands out as an energy intensive process, so
more energy efficient options for drying are worth exploring.
Using a renewable energy source for drying could reduce cli-
mate change. In the fibre processing stage, heating of retting
water also adds to the environmental impacts. Use of a renew-
able energy source (wood pellets) is an appropriate choice with
regards to climate change. The possibility of reducing retting
duration from 72 h to, for example,48 h is worth exploring, as it
would reduce energy use for maintaining the water tempera-
ture. A reduced water-fibre ratio at retting would also decrease
the energy use in retting. The rinsing water is not heated, but
possibilities for reducing water use in this process should be
investigated, as lower water use is an aim in itself.
6. Conclusions and perspectives
LCA methodology was used to evaluate the environmental
impacts of three hemp yarn production scenarios and a flax
yarn production scenario. The comparison of traditional warm
water retting based hemp processing with its two newly pro-
posed alternatives and with flax revealed that, overall, neither
of the alternatives was unambiguously better than the ref-
erence. The environmental impacts of the hemp reference
scenario and the flax scenario were very similar, except for
pesticide use (higher for flax) and water use (higher for hemp).
A reduction of the environmental impacts associated with
the production of hemp yarn should give priority to reduc-
tion of energy use in the fibre processing and yarn production
stages and to reduction of eutrophication in the crop produc-
tion phase.
If yields can be improved, not only in agriculture, but in
every processing step, without increasing inputs, impacts per
kilogram of final product will decline and benefits (environ-
mental and economic) will increase. Hemp breeders have been
concentrating on developing varieties with increased fibre
content. It seems, however, that less than 30% of the total
amount of fibre is recovered as long fibre, so an additional
goal should be to maximise the yield of long fibre. The opti-
misation of fibre processing should also be an important goal.
The West-European flax sector has worked intensively for the
last 20 years to maximise the yield of long fibre and they now
harvest the fruits of this development.
Technological developments seem crucial for the develop-
ment of the hemp textile industry in Europe. Contemporarily,
significant amounts of hemp long fibres are only produced
in Eastern Europe, mainly Hungary and Romania, where the
labour costs are low. The level of mechanisation of the current
production methods, which correspond largely to the hemp
water-rettingscenario, is low and the technology is not directly
transferable to Western Europe. In the long run it will probably
encounter problems in Eastern Europe too. Therefore, techno-
logical development, in particular aiming at the reduction of
labour requirements, is essential for the successful produc-
tion of hemp textiles in Europe. In this respect, the hemp
bio-retting scenario investigated here seems to offer a promis-
ing potential to develop into a method combining a low labour
requirement and a satisfactory environmental profile.
Each investigated production scenario is associated with
an “environmental profile”, which was assessed in this study.
What has not been done is to consider the actual fibre/yarn
quality along with the environmental impacts. Besides the
environmental sustainability of an agro-industrial produc-
tion system, the fibre quality is indeed an important aspect,
since it is the foundation of any successful spinning oper-
ation. Throughout this study we have assumed that the
different scenarios yield long fibre of similar quality, but
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10 industrial crops and products 27 (2008) 1–10
this can be questioned. Fibre quality is a focal issue within
the HEMP-SYS project and it would be very interesting and
“enlightening” to combine the LCA results with the analysis
of fibre quality obtained from different scenarios. It would
bring us one step closer to finding the most sustainable fibre
scenario—remembering that the concept of sustainability has
three dimensions: environmental, social and economic.
Acknowledgements
This research was carried out with the contribution of the
EU in the Project QLK5-CT-2002-01363 “HEMP-SYS—Design,
Development and Up-Scaling of a Sustainable Production
System for Hemp Textiles: an Integrated Quality Systems
Approach”. The authors are solely responsible for the data
and opinion herein presented, which does not represent the
opinion of the Community. We want to thank two anonymous
reviewers for helpful comments which allowed us to improve
the manuscript.
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