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Euphytica 140: 13–23, 2004.
C
2004 Kluwer Academic Publishers. Printed in the Netherlands. 13
Life Cycle Analysis of field production of fibre hemp, the effect of production
practices on environmental impacts
Hayo M.G. van der Werf
INRA, UMR Sol, Agronomie et Spatialisation de Rennes-Quimper, ENSAR - 65, rue de Saint Brieuc CS 84215,
35042 Rennes Cedex, France; (e-mail: Hayo.vanderWerf@roazhon.inra.fr)
Key words: Cannabis sativa L., environmental impact, eutrophication, farmer practices, fibre hemp, Life Cycle
Assessment
Summary
Life Cycle Assessment (LCA) was used to assess the environmental impacts of field production of fibre hemp
and seven other crops in France. The production of 1 ha of hemp yielded a eutrophication potential of 20.5 kg
PO4-equivalents, a global warming potential of 2330 kg CO2-equivalents, an acidification potential of 9.8 kg SO2-
equivalents, a terrestrial ecotoxicity potential of 2.3 kg 1,4-dichlorobenzene-equivalents, an energy use of 11.4 GJ,
and a land use of 1.02 ha.year. A comparison of hemp (low impacts), wheat (intermediate impacts) and sugar beet
(high impacts) revealed that the crops were similar for the relative contributions of emitted substances and resources
used to impacts, and for the relative contribution of processes to impacts. A reduction of the impacts of hemp
production should focus on eutrophication, and consider the reduction of climate change, acidification and energy
use as secondary objectives. Given this objective, the overall environmental effect of the substitution of mineral
fertiliser by pig slurry is negative. The introduction of reduced tillage is of interest, as it decreases energy use,
acidification and climate change. Measures leading to a reduction in NO3leaching are highly interesting, as they
strongly decrease eutrophication. Implications for hemp breeding are discussed.
Introduction
From 16th to 18th century, hemp (Cannabis sativa L.)
and flax (Linum usitatissimum L.) were the major
fibre crops in Russia, Europe and North America
(Pounds, 1979; Abel, 1980). Both crops were used for
the production of fabrics for garments. Worn-out flax
and hemp fabrics were used as raw materials in paper
mills. However, the large-scale cultivation of cotton
(Gossypium L.), jute (Corchorus olitorius L.) and
other tropical fibres, caused the world area of hemp
and flax to decline in the 19th century. This decline
has continued in the 20th century, due to the advent
of synthetic fibres. The presence of psychoactive
components in hemp contributed to its decline, as this
became a reason to prohibit hemp cultivation in many
countries (Dempsey, 1975). In 1984, world hemp area
was 403,000 ha, in 1993 it was 117,000 ha and in
2003 it had further declined to 74,000 ha (FAO, 2004).
In spite of this overall decline, in Europe hemp area
increased from 7,000 ha in 1993 to 18,000 ha in 2003
(Karus, 2004).
From the Second World War until the 1980’s, hemp
wasalargely forgotten crop. However, in eastern and
central Europe and in France breeding work continued
(De Meijer, 1995), leading to more productive hybrid
varieties, increased fibre contents (B´ocsa, 1995) and
very low contents of psychoactive substances (Fournier
et al., 1987).
The potential of hemp as an attractive crop for sus-
tainable fibre production was pointed out in the early
1980s (Hanson, 1980). Its yield was reported to be high,
and it was said to improve soil structure (Du Bois,
1982). Furthermore, hemp was claimed to suppress
weeds effectively, and to be virtually free from diseases
or pests.
14
In January 1990, a comprehensive 4-year study was
started in the Netherlands to investigate the potential
of fibre hemp as a new raw material for the pulp and
paper industry. This programme concluded that hemp
is agronomically attractive, as most of the claims made
by early hemp advocates proved to be true (vander Werf
et al., 1995): hemp can supply high fibre yields, requires
little or no pesticide and suppresses weeds and some
major soil-borne diseases. However, in the maritime
climate of the Netherlands the crop is not disease-free,
as the fungus Botrytis cinerea can cause severe damage
in wet years (van der Werf et al., 1995). In spite of
this, hemp manifestly will fit into sustainable farming
systems (van der Werf et al., 1996).
Intensive cotton production has been severely
criticised for its negative effects on the environment:
intensive use of pesticides (cotton can be treated 20
times per season), high fertiliser and irrigation re-
quirements (Pimentel et al., 1991; WWF, 1999). These
problems can be reduced to some extent by introducing
integrated pest management techniques, or by shifting
to organic farming methods (Pimentel et al., 1991;
Pleydell-Bouverie, 1994). A comeback of hemp as a
raw material for textile may contribute to the sustain-
ability of the textile industry. Relative to cotton, hemp
can be produced more sustainably, as it requires little or
no pesticide and its fertiliser requirements are modest.
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 de-
velopment 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 textiles, coupled to an in-
tegrated quality system for stems, raw and processed
fibres, yarns and fabrics based on eco-labelling criteria.
Given this objective, the project should include an as-
sessment of the environmental impacts associated with
the life cycle of hemp textile products.
Many studies have been conducted concern-
ing the environmental impacts associated with the
production of field crops such as wheat (Triticum
aestivum)(Audsley et al., 1997), sugar beet (Beta
vulgaris) (Brentrup et al., 2001) tomato (Lycopersicon
esculentum) (Andersson et al., 1998) and biomass
crops (Reinhardt & Zemanek, 2000). In fibre hemp,
a single study was found (Patyk & Reinhardt, 1998):
a screening Life Cycle Analysis of hemp products,
including the processes: cultivation and harvest, press-
ing of oil, decortication, steam pressure digestion and
textile production. Relative to the impacts associated
with the whole of these processes, this preliminary
study showed that crop production (i.e. cultivation and
harvest) accounted for 17% of climate change, 36%
of acidification and 10% of energy use. Unfortunately
the study did not assess eutrophication associated with
hemp products.
The present study aimed to quantify major impacts
associated with the field production of fibre hemp us-
ing Life Cycle Analysis, and to compare the impacts
of hemp to those of other annual crops. The effect
of modifications of farmer practices and of a more
favourable hypothesis with respect to nitrate leaching
wasexplored. The results of this study will be of use for
the evaluation of the environmental impacts of hemp
products, and may help to guide future breeding pro-
grammes.
Materials and methods
Evaluation methodology
Environmental impacts associated with crop produc-
tion were evaluated using Life Cycle Assessment
(LCA), which is a method to assess impacts associ-
ated with a product by quantifying and evaluating the
resources consumed and the emissions to the environ-
ment at all stages of its 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 disposal (Guin´ee et al.,
2002). In the Inventory Analysis phase, inputs from the
environment (resources used) and outputs to the envi-
ronment (emissions) associated with the product are
listed. In the Impact Assessment phase, inputs and out-
puts are interpreted in terms of environmental impacts
(Guin´ee et al., 2002).
The present study deals with the field production
of fibre hemp and seven other major arable crops in
France; only the processes up to (and including) the
harvest, the transport to the farm and the on-farm drying
of the harvested product (the latter applying only for
maize) were considered. Emissions and resource use
were expressed per ha.
Data concerning resource use and emissions associ-
ated with the production and delivery of several inputs
for crop production (fertilisers, pesticides, tractor fuel,
and agricultural machinery) were derived according to
Nemecek and Heil (2001). The production of seed for
sowing was taken into account, we assumed that inputs
required for the production of seed for sowing were
15
Table 1. Inputs, yield and nitrate-N emitted (all in kg/ha) according to a Good agricultural practice production scenario for hemp and other
major arable crops produced in France
Hemp Sunflower Rape seed Pea Wheat Maize Potato Sugar beet
N (ammonium nitrate) 75 85 110 0 130 100 170 220
P2O5(triple superphosphate) 38 32 41 46 64 51 80 101
K2O (potassium chloride) 113 21 30 95 90 30 293 180
CaO 333 167 167 333 333 333 0 333
Seed for sowing 55 5 2.5 200 120 20 2,000 2.5
Pesticide (active ingredient) 0 1.0 2.9 3.2 2.9 3.5 5.5 3.7
Diesel 65 79 81 87 101 91 165 137
Natural gas (for grain drying) 0 0 0 0 0 167 0 0
Agricultural machinery 16.4 23.0 23.3 26.9 28.7 21.3 29.0 34.2
Grain dry matter yield – 2,100 2,970 4,110 5,910 6,440 – –
Stem/straw dry matter yield 6,720 – – 1,410 3,870 – – –
Sugar/tuber dry matter yield – – – – – – 10,000 11,540
Followed by catch crop (%) 100 0 050 000
Succeeding crop wheat wheat wheat wheat maize wheat wheat wheat
NO3-N emitted 40 40 40 70 40 40 40 40
1Indicates the percentage of cases for which a catch crop is assumed to be sown between harvest of the crop and sowing of the succeeding
crop.
identical to those required for the production of the
crop for which the seed was used as an input. When pig
slurry was used as a fertiliser, emissions and resource
use associated with its production and delivery were not
included in this analysis, because they were allocated to
pig production, as recommended by Wegener Sleeswijk
et al. (1996). Data for energy carriers and for road trans-
port were from the BUWAL 250 database (BUWAL,
1996). Buildings were not included in the analysis due
to lack of data, the contribution of buildings to overall
impacts of arable crops production has been shown to
be minor (0–2%) (van Zeijts & Reus, 1996).
Crop production
For all crops, farmer practices were according to a
reference scenario: Good Agricultural Practice, i.e.
fertilisation according to anticipated crop needs, and
integrated pest management. Input use for hemp was
based on van der Werf (2002), for rape seed (Brassica
napus L.), pea (Pisum sativum L.), wheat and maize
(Zea mays L.) input use was based on interviews with
experts (B. Goutte and A. Cottet, personal communi-
cation). Input use for sugar beet was based on Le Clech
(1999), input use for sunflower (Helianthus annuus)
was according to Cederberg (1998), input use for
potato (Solanum tuberosum L.) was according to ITCF
(1995). Yield levels were averages for 1996–2000
(AGRESTE, 2001; FAO, 2002). Input use and yield
levels for the crops are summarised in Table 1.
For hemp, the effect of modifications of farmer
practices (use of pig slurry and reduced tillage)
and of reduced nitrate leaching was explored. The
environmental impacts of the reference scenario
(Good Agricultural Practice) were compared to three
alternative scenarios (Table 2).
Emissions associated with crop production
Ammonia emissions due to application of ammonium
nitrate fertiliser were estimated according to ECETOC
(1994): emission factor (EF) was 0.02 kg of NH3-N per
kg N applied. Total ammonia nitrogen (TAN =NH3+
NH4+) content of applied pig slurry was 3.17 kg/t. EF
for NH3volatilisation following field application of
slurry (on cultivated soil in early April, incorporation
within 24 h) was 0.15 kg of NH3-N per kg of TAN
(Morvan & Leterme, 2001).
With respect to losses of nitrate nitrogen (NO3-N)
to groundwater (Table 1), crops were assigned to one
of four leaching risk classes: very minor (15 kg/ha),
minor (40 kg/ha), moderate (70 kg/ha) and large (100
kg/ha). Assignment of leaching risk was based on crop-
specific values of NO3present in the soil at harvest
16
Table 2. Inputs, yield and nitrate-N emitted (all in kg/ha) according to four production scenarios for
hemp produced in France
Good
agricultural Reduced
practice Pig slurry tillage Less leaching
Pig slurry 20,000
N (ammonium nitrate) 75 0 75 75
P2O5(triple superphosphate) 38 0 38 38
K2O (potassium chloride) 113 51 113 113
CaO 333 333 333 333
Seed for sowing 55 55 55 55
Pesticide (active ingredient) 0 0 0 0
Diesel 65 72 39 65
Agricultural machinery 16.4 18.8 11.6 16.4
Straw dry matter yield 6,720 6,720 6,720 6,720
Followed by catch crop (%)10000
Succeeding crop wheat wheat wheat wheat
NO3-N emitted 40 40 40 20
All scenarios assume Good Agricultural Practice.
1Indicates the percentage of cases for which a catch crop is assumed to be sown between harvest of the
crop and sowing of the succeeding crop.
in autumn, leaching losses calculated with the LIXIM
simulation model (Mary et al., 1999), and the length
of the period between harvest and the establishment of
the succeeding (catch) crop.
Emissions of nitrous oxide nitrogen (N2O-N) were
estimated according to Mosier et al. (1998): for di-
rect emissions from soils EF was 0.0125 kg of N2O-
Nper kg N input from synthetic and organic fertiliser
and biological N-fixation, after subtraction of ammonia
emissions EF was 0.01 kg of N2O-N per kg of NH3-
N emitted and 0.025 kg of N2O-N per kg of NO3-N
emitted. Emissions of nitric oxide nitrogen (NOx-N)
were estimated according to Rossier (1998) at 10% of
emissions of N2O-N.
Run-off of PO4-P to surface water was estimated
according to Rossier (1998): an EF of 0.01 kg of PO4-P
per kg P input from synthetic and organic fertiliser was
used. Emissions of Cd, Cu, Ni, Pb and Zn to the soil
were calculated according to a balance approach, con-
sidering input by synthetic and organic fertilisers and
output via harvested produce. Heavy metal content of
fertilisers was based on Rossier (1998), except for Cu
and Zn in slurry, which were based on Baudet (1999).
Data on heavy metal uptake of crops were rare. There-
fore the same reference uptake was used regardless of
the crop. Reference uptake was based on a wheat crop
yielding 6800 kg/ha of grain containing 0.12 mg/kg of
Cd, 5.9 mg/kg of Cu, 0.22 mg/kg of Ni, 0.2 mg/kg of Pb
and 31 mg/kg of Zn (contents based on Audsley et al.,
1997 and Baize, personal communication). Pesticides
and their metabolites were not taken into account in
this study, as appropriate characterisation factors are
lacking for many substances.
Characterisation factors
In the Life Cycle Impact Assessment phase, it is first
determined which impact categories will be consid-
ered. In this study the following impact categories were
considered: eutrophication, climate change, acidifica-
tion, terrestrial ecotoxicity, energy use and land use.
Next, the indicator result for each impact category is
determined. This is done by multiplying the aggregated
resources used and the aggregated emissions of each
individual substance with a characterisation factor for
each impact category to which it may potentially con-
tribute (Heijungs et al., 1992). Characterisation factors
are substance-specific, quantitative representations of
the additional environmental pressure per unit emission
of a substance (Huijbregts et al, 2000). The character-
isation factors used in this study are given below for
each impact category.
17
Eutrophication covers all potential impacts of high
environmental levels of macronutrients, in particular
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 was defined here as the impact of
emissions on the heat radiation absorption of the at-
mosphere. As recommended by Guin´ee et al. (2002),
Global Warming Potential for a 100 year time hori-
zon (GWP100)was calculated according to the GWP100
factors by IPCC (Houghton et al., 1996) in kg CO2-
equivalents, CO2:1,N
2O: 310, CH4: 21.
Acidifying pollutants have a wide variety of im-
pacts on soil, groundwater, surface waters, biological
organisms, ecosystems and materials (buildings). As
recommended by Guin´ee et al. (2002), Acidification
Potential (AP) was calculated using the average Eu-
ropean AP factors by Huijbregts (1999a) in kg SO2-
equivalents, NH3: 1.6, NO2: 0.5, NOx: 0.5, SO2: 1.2.
Terrestrial ecotoxicity refers to impacts of toxic
substances on terrestrial ecosystems. As recommended
by Guin´ee et al. (2002), Terrestrial EcoToxicity Poten-
tial (TETP) was calculated using the TETP factors for
infinite time horizon and global scale by Huijbregts
(1999b) in kg 1,4-dichlorobenzene-equivalents (DCB-
eq.), Cd: 170, Cu: 14, Ni: 240, Pb: 33, Zn: 25.
Energy use refers to the depletion of energetic re-
sources. 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, natu-
ral gas: 35 MJ/m3, uranium: 451000 MJ/kg, coal: 18
MJ/kg, lignite: 8 MJ/kg, gas from oil production 40.9
MJ/m3.
Land use 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 quan-
titative assessment, which does not distinguish quality
of land use.
Table 3. The environmental impacts due to the field production of hemp (1 ha) and other major arable crops in France, according to a Good
agricultural practice production scenario
Impact category Unit Hemp Sunflower Rape seed Pea Wheat Maize Potato Sugar beet
Eutrophication kg PO4-eq. 20.5 20.2 20.6 34.4 21.9 21.0 23.8 24.1
Climate change kg CO2-eq. 2,330 2,300 2,700 2,890 3,370 3,280 4,120 4,900
Acidification kg SO2-eq. 9.8 10.8 12.8 8.3 16.3 13.6 22.4 24.5
Terrestrial ecotoxicity kg 1,4-DCB-eq. 2.3 1.8 2.5 0.1 4.0 3.0 4.9 6.7
Energy use MJ 11,400 11,900 13,800 11,800 18,100 23,000 25,600 26,300
Land use m2.year 10,200 10,000 10,000 10,500 10,200 10,100 10,400 10,200
Results
Input use and impacts for eight annual crops
Input use was quite variable for the crops (Table 1):
from 0 (pea) to 220 (sugar beet) kg/ha for N, from
32 (sunflower) to 101 (sugar beet) kg/ha for P2O5,
from 0 (hemp) to 5.5 (potato) kg/ha for pesticide active
ingredient, and from 65 (hemp) to 165 (potato) kg/ha
for diesel. Hemp and sunflower can be consistently
characterised as low-input crops, whereas potato and
sugar beet can be characterised as high-input crops.
Impacts were very variable, depending on the crop
(Table 3). Differences were smallest for land use
(range 10,000–10,500) and largest for terrestrial eco-
toxicity (range 0.1–6.7). For climate change (range
2,300–4,900), acidification (range 8.3–24.5) and en-
ergy use (range 11,400–26,300) variability was quite
large, for eutrophication (range 20.2–34.4) it was rela-
tively modest.
Eutrophication was low (about 20 kg PO4-eq.) for
hemp, sunflower and rape seed, and high (34 kg PO4-
eq.) for pea (Table 3). Climate change was low for
hemp and sunflower (2300 kg CO2-eq.) and high for
potato (4120) and sugar beet (4900). Acidification was
low for pea, hemp and sunflower (8–11 kg SO2-eq.)
and high for potato and sugar beet (22–25). Terrestrial
ecotoxicity was very low for pea (0.1 kg 1,4-DCB-
eq.), low for sunflower, hemp and rape seed (1.8–2.5)
and high for potato and sugar beet (4.9–6.7). Energy
use was low for hemp, pea and sunflower (11,400–
11,900 MJ), and high for maize, potato and sugar
beet (23,000–26,300). For land use differences were
negligible.
For all impact categories (except land use), values
were consistently low for hemp and sunflower, and con-
sistently high for potato and sugar beet. For rape seed
and pea, the impact values were rather low, and for
wheat and maize impacts were of intermediate level.
18
Table 4. The contribution of the field production of 1 ha of hemp to environmental impacts in western Europe for six impact categories
Annual per Reference for annual
Impact category Unit capita impacts per capita impacts Contribution (%)
Eutrophication kg PO4-eq. 38.4 Huijbregts et al., 2001 53.3
Climate change kg CO2-eq. 14,600 Huijbregts et al., 2001 15.9
Acidification kg SO2-eq. 84.2 Huijbregts et al., 2001 11.7
Terrestrial ecotoxicity kg 1,4-DCB-eq. 146 Huijbregts et al., 2001 1.6
Energy use MJ 154,000 PR´e Consultants, 1997 7.4
Land use m2.year 10,100 Huijbregts et al., 2001 101.4
Contributions are calculated by dividing impacts for 1 ha of hemp (Table 2) by annual per capita impacts for western Europe in 1995.
Relative contribution of hemp field production
to overall impacts in western Europe
In order to assess the relative contribution of hemp
crop production to overall environmental impacts in
Europe, impacts for the field production of 1 ha of
hemp were divided by the total impacts per person for
western Europe in 1995 (Huijbregts et al., 2001; PR´e
Consultants, 1997) (Table 4). This normalisation re-
vealed that the contribution of hemp production to land
use (101%) and eutrophication (53%) was very impor-
tant, and that its contribution to terrestrial ecotoxicity
Table 5. The contributions (in %) to different impact categories of emitted substances and resource use
associated with the field production of hemp, wheat and sugar beet
Substances/
Impact category resources Hemp Wheat Sugar beet
Eutrophication NO388.6 82.4 75.1
NH33.1 5.1 7.9
PO43.4 5.4 7.7
NO24.9 7.1 9.3
Climate change N2O 56.2 56.6 58.7
CO242.8 42.3 40.3
CH41.0 1.1 1.0
Acidification NH329.9 31.6 35.5
SO231.1 31.9 29.7
NO239.0 36.5 34.8
Terrestrial ecotoxicity Zn 0 0 2.4
Ni 70.2 67.5 65.7
Pb 3.5 4.0 3.2
Cd 26.3 28.5 28.7
Energy use Crude oil 44.7 45.8 43.7
Natural gas 32.7 32.1 36.4
Uranium 11.4 10.6 9.0
Coal 9.3 9.5 8.8
Others 1.9 2.0 2.1
was minor (1.6%). Its contribution to energy use (7%),
acidification (12%) and climate change (16%) was in-
termediate.
The contribution of emitted substances to impacts
The contribution of emitted substances and resources
used to impact values was examined for hemp (char-
acterised by low impact values), wheat (intermediate
impact values) and sugar beet (high impact values)
(Table 5). For the three crops, eutrophication was
mainly (75–89%) due to NO3. Climate change was
19
mainly due to N2O (56–59%) and CO2(40–43%).
Acidification was due to emissions of NH3,SO
2, and
NO2, with the three substances contributing similarly.
Terrestrial ecotoxicity was mainly due to emissions of
Ni (66–70%) and Cd (26–29%). Energy use was mainly
due to crude oil (44–46%) and natural gas (32–36%).
Although the three crops differed strongly with
respect to the use of inputs and the level of impact
values obtained, only minor differences were found for
the relative contribution of substances and resources
to impacts.
Table 6. The contributions (in %) to different impact categories of the processes (production of crop inputs, production
and use of diesel, field emissions) making up the field production of hemp, wheat and sugar beet
Impact category (unit) Processes Hemp Wheat Sugar beet
Eutrophication N fertiliser production 1.0 1.5 2.4
P fertiliser production 1.1 1.7 2.5
K fertiliser production 0.1 0.1 0.1
CaO production 0.2 0.2 0.2
Pesticide production 0 0.1 0
Machinery production 0.2 0.4 0.4
Diesel production and use 2.7 4.0 4.9
Field emissions194.7 92.0 89.5
Climate change N fertiliser production 24.6 29.5 34.4
P fertiliser production 2.8 3.3 3.5
K fertiliser production 2.6 1.4 1.9
CaO production 13.1 9.0 6.2
Pesticide production 0 0.6 0.5
Machinery production 5.3 6.4 5.3
Diesel production and use 10.5 11.3 10.5
Field emissions141.1 38.5 37.7
Acidification (kg SO2-eq.) N fertiliser production 11.8 12.4 14.0
P fertiliser production 10.7 10.8 11.3
K fertiliser production 2.2 1.1 1.4
CaO production 3.3 2.0 1.3
Pesticide production 0 1.7 1.4
Machinery production 12.5 13.3 10.5
Diesel production and use 26.2 24.4 22.1
Field emissions133.3 34.3 38.0
Energy use (MJ) N fertiliser production 28.1 30.7 35.9
P fertiliser production 5.6 6.0 6.5
K fertiliser production 9.8 4.9 6.8
CaO production 8.5 5.3 3.6
Pesticide production 0 4.2 3.7
Machinery production 19.3 21.2 17.5
Diesel production and use 28.7 27.7 26.0
1All field emissions, except for those resulting from the field use of diesel, which are accounted for in “Diesel
production and use.”
The contribution of processes to impacts
The contribution of processes (production of crop
inputs, production and use of diesel, and field emis-
sions) was examined for hemp (low impacts), wheat
(intermediate impacts) and sugar beet (high impacts)
(Table 6). For the three crops eutrophication was very
largely (90–95%) due to field emissions. Climate
change was mainly due to field emissions (38–41%), N
fertiliser production (25–34%), diesel production and
use (11%) and CaO production (6–13%). Acidification
20
was mainly due to field emissions (33–38%), diesel
production and use (22–26%), N fertiliser production
(12–14%), P fertiliser production (11%) and machin-
ery production (11–13%). Terrestrial toxicity was
due exclusively to field emissions (data not shown).
Energy use was mainly due to N-fertiliser production
(28–36%), diesel production and use (26–29%) and
machinery production (18–21%).
Although the three crops differed strongly with re-
spect to the use of inputs and the level of impact values
obtained, only minor differences were found for the
relative contribution of processes to impacts.
The effect of alternative scenarios for hemp
production
In many areas pig slurry is available at very low cost,
its use may reduce production costs. Substitution of
mineral fertiliser by pig slurry strongly reduced climate
change (−24%) and energy use (−32%) but increased
eutrophication (+16%), acidification (+140%) and
terrestrial ecotoxicity (+1720%) (Table 7). Reduced
tillage is of interest to farmers as it reduces erosion,
production costs and labour requirements. The re-
duced tillage scenario affected climate change (−6%),
acidification (−13%) and energy use (−16%).
The amount of nitrate leached, associated with an
arable crop, will be lower when the amount of nitrate
left in the soil at harvest is small, when the length of
the period between harvest and the next crop is short
or when the precipitation during this period is reduced.
The scenario assuming reduced leaching reduced eu-
trophication (−43%) and climate change (−10%).
Discussion
This study compared the potential environmental
impacts of fibre hemp to the impacts of seven major
Table 7. The environmental impacts due to the field production (1 ha) of hemp according to four production scenarios
Good agricultural Reduced
Impact category Unit practice Pig slurry tillage Less leaching
Eutrophication kg PO4-eq. 20.5 23.7 20.2 11.6
Climate change kg CO2-eq. 2,330 1,770 2,200 2,090
Acidification kg SO2-eq. 9.8 23.5 8.5 9.8
Terrestrial ecotoxicity kg 1,4-DCB-eq. 2.3 41.9 2.3 2.3
Energy use MJ 11,400 7,760 9,520 11,400
Land use m2.year 10,200 10,200 10,200 10,200
arable crops, in the context of farmer practices and
pedoclimatic conditions of France. Quantitative
information on the environmental impact of hemp
field production is scarce. Patyk and Reinhardt (1998)
carried out a preliminary LCA of hemp production for
Germany, supplying results for energy use, climate
change and acidification. Their result for energy
use (12,300 MJ/ha) is close to our result (11,400),
the values they obtained for acidification (6.6 kg
SO2-eq.) and for climate change (1421 kg CO2-eq.)
are lower than the results reported here (9.8 and 2330,
respectively). Patyk and Reinhardt (1998) do not give
sufficient methodological detail to allow an analysis
of the reasons for this discrepancy.
This study has revealed major differences in input
use and environmental impacts for the crops compared.
Further, it has been shown that low-input crops tend to
be also low impact crops, whereas high-input crops
have high impacts. Hemp and sunflower are low-input
crops, with respect to the use of fertilisers, pesticides,
diesel and agricultural machinery. These two crops
have consistently lower impact values than the other
crops studied, for all impact categories examined here,
with the exception of land use. Land use is the only im-
pact category for which all the crops studied show only
minor differences. This is not surprising, as the only ori-
gin for the differences found in land use lies in the land
surface required for the production of seed for sowing
one hectare of the crop. Although this surface is quite
different from one crop to another (it may vary from 10
to 500 m2), its overall contribution to land use is small,
relative to the 10,000 m2required to grow the crop.
A detailed comparison of hemp (a low-impact
crop), wheat (of intermediate impact) and sugar beet
(high-impact) revealed that, despite major differences
in the level of impact values, only minor differences
were found both for the relative contribution of sub-
stances and resources to impacts, as well as for the
relative contribution of processes to impacts.
21
Although the environmental impacts associated
with the production of fibre hemp are smaller than those
associated with most other crops, an examination of
possible pathways to further reduce hemp’s impacts is
of obvious interest. Relative to the overall environmen-
tal impacts in Europe, the contribution of hemp pro-
duction to land use (101%) and eutrophication (53%)
is very important. However, the importance of the
land use impact category will depend on the regional
and national context. In a densely populated country,
like for instance the Netherlands, agriculture, industry,
housing and infrastructure compete for land, and land
use is considered to be at least as important as the other
impact categories. In France, on the other hand, com-
petition for land is less, and land use is of secondary
importance. Eutrophication, however, is considered
a major problem in France, as elsewhere in Europe.
While hemp’s contribution to terrestrial ecotoxicity
was minor (1.6%), its contribution to energy use (7%),
acidification (12%) and climate change (16%) was
found to be intermediate. A reduction of the environ-
mental impacts associated with the production of hemp
should therefore give priority to reduction of eutroph-
ication, and consider the reduction of climate change,
acidification and energy use as secondary objectives.
Given this objective, the substitution of mineral fer-
tiliser by pig slurry is not an appropriate option, as,
although it decreases climate change and energy use
(both due to a reduced use of mineral fertiliser), this
comes at the prize of an increase in eutrophication and
a major increase in acidification, both of which are
caused by the fact that the use of slurry leads to much
larger emissions of NH3than the use of mineral fer-
tiliser. Finally, the use of slurry brings about a major
increase in terrestrial ecotoxicity, due to the presence
of Cu and Zn in pig slurry. Although the use of slurry
instead of mineral fertiliser may be of economic inter-
est, its overall effect on the environmental performance
of hemp is negative.
The introduction of reduced tillage is an appropri-
ate option. Although it does not affect eutrophication,
it does reduce energy use, acidification and climate
change. These effects result from the reduced use of
diesel and agricultural machinery. Reduced tillage fur-
thermore generates additional environmental benefits,
such as reduced erosion risks and increased soil organic
matter content (Uri et al., 1998).
Any measures leading to a reduction in NO3leach-
ing are of high interest, as a 50% reduction of the
amount of NO3leached reduced eutrophication by 43%
and climate change by 10%. Whereas the reduction of
eutrophication results directly from a lower emission of
NO3, the effect on climate change is indirect, resulting
from reduced emission of N2O due to denitrification
of NO3.Ingeneral, the optimisation of nitrogen fertili-
sation and the reduction of the period between harvest
and the establishment of the next (catch) crop are the
principal measures recommended to reduce NO3leach-
ing (Gustafson et al., 2000). However, fertilisation was
optimised in our scenarios, therefore a rapid establish-
ment of the next crop or of a catch crop seems the most
promising measure to reduce nitrate emissions.
Future breeding efforts may also contribute to re-
ducing the environmental impacts of hemp produc-
tion, in particular by carrying out breeding programmes
under conditions of reduced inputs. Our results have
shown that it would be of particular interest to focus on
conditions combining lower nitrogen fertilisation lev-
els (limiting nitrate leaching) and reduced soil tillage.
Genotypic variability has been demonstrated for both
nitrogen uptake and nitrogen use efficiency in wheat
(Le Gouis et al., 2000), maize (Singh et al., 1998) and
many other crops. An exploration of variability for this
trait in hemp would be of major interest. Although we
did not find any results assessing genotypic variabil-
ity relative to crop performance under conditions of
reduced tillage, we think this might also be a promis-
ing path to explore, for the creation of future hemp
cultivars.
Conclusions
This study assumed crop production practices accord-
ing to Good Agricultural Practise (GAP). GAP in
France is largely similar to GAP elsewhere in western
Europe; therefore we conclude that the results of this
study, though based on data from France, can be con-
sidered to hold true more generally for all of western
Europe.
Relative to the other crops examined in this study,
hemp and flax are low-input and low-impact crops.
The difference is most important relative to potato and
sugar beet, which can be characterised as high-input
and high-impact crops.
In spite of major differences among the crops with
respect to the level of impact values, only minor differ-
ences were found both for the relative contribution of
substances and resources to impacts, as well as for the
relative contribution of processes to impacts.
A reduction of the environmental impacts associ-
ated with the production of hemp should give priority
22
to reduction of eutrophication, and consider the reduc-
tion of climate change, acidification and energy use as
secondary objectives.
Acknowledgements
The author would like to thank C. Basset-Mens for
data collection and calculations concerning the potato
crop. This research was carried out with the contribu-
tion 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 author
is solely responsible for the data and opinion herein
presented, and does not represent the opinion of the
Community.
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