Directory UMM :Data Elmu:jurnal:A:Agricultural Systems:Vol66.Issue3.Dec2000:
Agricultural Systems 66 (2000) 167±189
www.elsevier.com/locate/agsy
Quantifying the environmental impact of
production in agriculture and horticulture in
The Netherlands: which emissions do we need
to consider?
J.C. Pluimers a,*, C. Kroeze a, E.J. Bakker b, H. Challa c,
L. Hordijk a
a
Environmental Systems Analysis Group, Wageningen University, PO Box 9101, 6700 HB Wageningen,
The Netherlands
b
Department of Mathematics, Wageningen University, Wageningen, The Netherlands
c
Department of Agricultural Engineering and Physics, Wageningen University, Wageningen, The Netherlands
Received 18 February 1999; received in revised form 25 July 2000; accepted 25 August 2000
Abstract
This study focuses on the environmental impact of agricultural production. The aim of the
study is to identify the most important sources of greenhouse gases, acidifying and eutrophying compounds in Tomato Cultivation, Greenhouse Horticulture and Total Agriculture in
The Netherlands. Within each of these three sectors we distinguish two systems. The System
Agriculture (System A) includes the ®rst-order processes of the agricultural production chain
and the System Industry (System I) includes some second-order processes. Results indicate
that, in general, System A emissions exceed System I emissions. However, in some cases
emissions from System I are relatively high compared to System A emissions, and need to be
considered when quantifying the total environmental impact of agricultural production. For
example, acidifying emissions from the production of electricity and rockwool (both secondorder processes) contribute almost 25% to the total acidifying emissions from System
Greenhouse Horticulture A+I. # 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Environmental systems analysis; Agriculture; Protected cultivation
* Corresponding author.
0308-521X/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0308-521X(00)00046-9
168
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
1. Introduction
Agricultural production in The Netherlands contributes to various environmental problems. Well-known environmental problems due to agriculture are often
related to speci®c activities and sectors. Dutch greenhouse horticulture, for example, is associated with relatively large emissions of the greenhouse gas carbon
dioxide (CO2) resulting from the combustion of natural gas. At the level of the
total agricultural sector, on the other hand, the emissions of acidifying ammonia
from animal waste are usually considered a major contributor to environmental
problems.
Several studies have been published on the environmental impact of agricultural
production in The Netherlands. These studies dier in their choice of system
boundaries. Sometimes system boundaries are related to economic sectors at a
national scale (e.g. RIVM, 1997). In this way, emissions from fuel combustion in
farms are assigned to agriculture, while emissions from power plants are assigned to
the energy sector. Other studies on the environmental impact of agriculture focus
on the whole production chain of, for instance, a particular crop by using the
methodology of environmental Life Cycle Assessment (LCA) (Nienhuis and de
Vreede, 1994a, b; Wegener Sleeswijk et al., 1996). LCA is a tool for assessing the
environmental impact of a product (Heijungs et al., 1992). Characteristic for LCA is
that it aims to cover the entire life cycle from cradle to grave and to include all
relevant environmental problems related to the product analysed.
Formulation of system boundaries is part of the ®rst step in environmental systems analysis (Table 1) (Checkland, 1979; Wilson, 1984). Usually, environmental
systems analysis deals with policymaking and aims at ®nding solutions to complex
problems that arise in society by describing the system and analysing alternatives
to the system. When de®ning system boundaries, one needs to take into account
spatial as well as temporal aspects. The de®nition of system boundaries partly
depends on the focus and purpose of the study. When studying an economic sector, one may chose to de®ne sub-sectors to describe the most important aspects of
a heterogeneous sector. Temporal boundaries indicate whether the analysis focuses
Table 1
The methodology of systems analysis in six steps as described by Wilson (1984) and Checkland (1979)
Step 1 In the ®rst step the problem is de®ned. The system boundaries, level of aggregation and input
output relations are described
Step 2 In the second step the objectives of the analysis are clari®ed and the model demands are
appointed
Step 3 During the third step the system synthesised, i.e. a model is built, system functions are listed and
alternatives to the current situation are collected
Step 4 The system is analysed by using the model developed in the third step. Uncertainties are
deduced and the performance is compared with the objectives
Step 5 In the ®fth step the optimum system is selected. The decision criteria are described and the
consequences are evaluated
Step 6 During the last step the whole analysis and its conclusions are described
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
169
on the present situation or also includes past or future trends. In this study we
focus on system boundaries within the present horticultural and agricultural
production chain (Fig. 1).
When analysing the emissions of pollutants related to the agricultural sector, ideally, one would aim for a full LCA approach for all products of the agricultural
sector. However, this is not feasible because of the complexity and heterogeneity of
the agricultural sector and the amount of data and time needed for such an analysis.
The question then rises what parts of the production chain have to be described to
analyse a certain environmental problem related to agricultural production, without
performing full LCAs for all products involved; in other words, what are the system
boundaries and how can we decide which inputs, outputs and processes have to be
taken into account and which can be ignored? This study aims at contributing to an
answer to this question.
We focus on three sectoral aggregation levels in this study. Our primary interest is
the analysis of the environmental impact of the greenhouse horticultural sector in The
Netherlands, at a sectoral level resulting in recommendations to policy makers.
The greenhouse horticultural sector is a relatively heterogeneous sector, both in terms
of economic activities and with respect to its environmental impact. Rabbinge and
Van Ittersum (1994) formulated guidelines to cope with tensions between aggregation
levels. They recommend to include the next lower and next higher aggregation level
Fig. 1. Overview of System A(gricultural production) and System A+I(ndustry) and the three aggregation levels: sector Tomato Cultivation, sector Greenhouse Horticulture and sector Total Agriculture.
170
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
in systems analysis in order to determine the relation between the aggregation
levels. In our study we therefore will analyse system boundaries for Greenhouse
Horticulture (primary focus), Tomato Cultivation (a level lower) and Total Agriculture (a level higher).
The aim of this study is to identify the most important present-day emissions of
greenhouse gases, acidifying compounds and eutrophying compounds related to
agricultural production in The Netherlands. For this purpose we will estimate
emissions resulting from activities within the agricultural sector (i.e. ®rst-order processes) as well as answer the question whether emissions due to the production of
most important inputs for the agricultural sector, such as fertilisers, biocides and
electricity (second-order processes) need to be taken into account. We will include
the most important greenhouse gases [carbon dioxide (CO2), methane (CH4)
and nitrous oxide (N2O)], acidifying compounds [sulphur dioxide (SO2), nitrogen
oxide (NOx) and ammonia (NH3)], and eutrophying compounds [nitrogen (N) and
phosphorus (P)].
2. Methodology
In this section we ®rst describe the dierent systems included in the analysis (system de®nition). Next, the method for calculating the emissions (calculation of emissions and environmental impact) is presented and we list the source of emission data
or data used for the calculation of the emissions (data collection).
2.1. System de®nition: System A and System A+I
The agricultural sector is studied here at three dierent aggregation levels
(Tomato Cultivation, Greenhouse Horticulture, Total Agriculture). At each of
these levels two dierent systems are distinguished: System Agriculture and System Agriculture+Industry (Table 2, Fig. 1). Basically, System A (Agriculture) includes the inputs and outputs of the agricultural production system in a
strict sense (®rst-order processes). System I (Industry) includes the production
of electricity, fertilisers, biocides and rockwool, which we consider second-order
processes. The inputs and outputs of System A consist of direct production factors,
respectively, emissions resulting from the use of these direct production factors which include fossil fuels, fertilisers, biocides and rockwool. The inputs to
System I include indirect production factors while the output consists of fertilisers,
biocides, rockwool and electricity produced and the related emissions. Thus in
total we will consider six systems: System Tomato Cultivation A and A+I, System Greenhouse Horticulture A and A+I, and System Total Agriculture A
and A+I (Table 2). We will also quantify indirect N2O emissions as result from
N use in agriculture. These emissions are described in the IPCC emission calculation method (IPCC, 1997) and it is known that these N2O emissions account for
about one-third of the total agricultural N2O emissions worldwide (Mosier et al.,
1998).
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
171
Table 2
Description of the systems studied: System Tomato Cultivation Agriculture (A) and Agriculture and
Industry (A+I), System Greenhouse Horticulture A and A+I and System Agriculture A and A+I
System A
Tomato Cultivation
Greenhouse Horticulture Total Agriculture
Environmental impact
from use of gas, fertilisers,
biocides and rockwool
As Tomato Cultivation,
but Greenhouse
Horticulture includes
both soil and rockwool
cultivation
As Tomato Cultivation
System A+I As System A but including
the environmental impact
of the production of
electricity, fertilisers, biocides
and rockwool (System Industry)
Environmental impact from
fuel use and co-generation
in farms, soils and stables
As System A but including
the environmental impact
of the production of
electricity, fertilisers, biocides
and rockwool (System
Industry)
2.2. Calculation of emissions and environmental impact
We analysed the emissions of CO2, CH4 and N2O (greenhouse gases), SO2 (acidifying gas), NOx and NH3 (acidifying gases and eutrophying gases), NO3 and PO4
(eutrophying compounds). Most of the emissions are either estimated by using
emission inventory data from literature or calculated as a function of agricultural
activities and some emission factors (Tables 3 and 4):
EMISSION f ACTIVITY; EMISSION FACTOR
1
Activities in System A include use of energy, biocides and fertilisers (N and P). In
System A also the production of manure and processes resulting in NH3 emissions
from stables are included. System I describes the production of electricity, fertilisers,
biocides and rockwool.
For each of the compounds considered, the integrated impact of emissions is calculated as (Heijungs et al., 1992) (Table 5):
IMPACT EMISSION CLASSIFICATION FACTOR
2
In this analysis we use as classi®cation factors the Global Warming Potentials
(GWPs) de®ned by the IPCC (1997), and acidi®cation and eutrophication potentials
as described by Heijungs et al. (1992) (Table 5). The GWP is an index of cumulative
radiative forcing between the present and some chosen later time horizon caused by
a unit mass of gas emitted now, expressed relative to the reference gas CO2 (1 kg
CO2) (Houghton et al., 1995). Heijungs et al. (1992) describe classi®cation factors
for substances contributing to acidi®cation and eutrophication expressed in SO2equivalents and PO4-equivalents, respectively.
172
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
Table 3
Activity data for the calculation of the emissions from Tomato Cultivation, Greenhouse Horticulture and
Total Agriculture in The Netherlands as used in Eq. (1)
Activity
Value
Reference
Tomato Cultivation
Gas use
Electricity use
Fertiliser N use
Fertiliser P use
Rockwool use
Biocide use
8.79108 m3
1.25108 kWh
1733 ton N
409 ton P
12.8 kton
11.3 ton
KWIN, 1993
Nienhuis and de Vreede, 1994a
Nienhuis and de Vreede, 1994a
Nienhuis and de Vreede, 1994a
Van der Berg and Lankreijer, 1994; CBS, 1996
CBS, 1996, 1997b
Greenhouse Horticultureb
Gas use
Electricity use
Fertiliser N use in soil cultivation
Fertiliser N use in rockwool cultivation
Fertiliser P use in soil cultivation
Fertiliser P use in rockwool cultivation
Rockwool use
Biocide use
4.3109 m3
9.2108 kWh
4259 ton N
4500 ton N
868.6 ton P
924.9 ton P
25.2 kton
704 ton
Van der Velden et al., 1995
Van der Velden et al., 1995
Poppe et al., 1995, CBS, 1996
Poppe et al., 1995, CBS, 1996
Poppe et al., 1995, CBS, 1996
Poppe et al., 1995, CBS, 1996
IKC, 1995
Poppe et al., 1995
Total Agriculturec
Electricity use
Fertiliser use N
Fertiliser use P
Biocide use
Rockwool use
9 PJ
412 kton N
60 kton P
5812 ton
25 200 ton
CBS, 1997a
Kroeze, 1994
CBS, 1997a
CBS, 1997b
IKC, 1995; CBS, 1996
a
a
b
c
Area sector Tomato Cultivation is 1505 ha (CBS, 1996).
Area sector Greenhouse Horticulture is 10 144 ha (CBS, 1996).
Area sector Total Agriculture is 2106 ha (Kroeze, 1994).
2.3. Data for Tomato Cultivation and Greenhouse Horticulture
The emissions from Tomato Cultivation and Greenhouse Horticulture are estimated following Eq. (1). This requires input data on activities and related emission
factors. These data are listed in Tables 3 and 4, respectively.
For the production of fertilisers and biocides (both activities in System I) we distinguished between energy-related and process-related emissions (Table 4). Processrelated emissions are released during the chemical production process. Energy-related emissions are related to the production of energy used in the chemical process.
We assumed that all electricity used in the production of fertilisers and biocides is
produced by a coal-®red power plant and thus we used the same emission factors as
for electricity production (Table 4). This assumption can be considered a worst case
scenario, because in practice electricity is produced from a mix of fuels.
For Greenhouse Horticulture we distinguished between soil and rockwool cultivation. Based on the area of vegetables, ornamentals, soil and rockwool cultivation
(CBS, 1996) on the one hand and fertiliser use in vegetables and ornamentals on the
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
173
Table 4
Emission factors as used in Eq. (1) for the calculation of the emissions from Tomato Cultivation, Greenhouse Horticulture and Total Agriculture in The Netherlands
Activity
Emission factor
Emission factors related to activities in System A
Gas use
CO2
1.776 kg/m3 natural gas
N2O
7.2010ÿ5 kg/m3 natural gas
NOx
1.4210ÿ3 kg/m3 natural gas
9.510ÿ5 kg/m3 natural gas
CH4
Fertiliser use in soil cultivation in greenhouses
N-fertiliser use
N2O
0.03 kg N2O-N/kg N
NOx
0.025 kg NOx-N/kg N
0.35 kg NO3-N/kg N
NO3
P-fertiliser use
PO4
All emission factors are estimated
from the studies of Mosier et al.
(1998), Daum and Schenk (1996),
Sonneveld (1993) and Postma (1996)
All emission factors are estimated
from the studies of Mosier et al.
(1998), Daum and Schenk (1996),
Sonneveld (1993) and Postma (1996)
0.1 kg PO4-P/kgP
Emission factors related to activities in System I
Electricity production
CO2
0.834 kg/kWh
CH4
9.010ÿ6 kg/kWh
N2O
1.2610ÿ5 kg/kWh
NOx
1.3510ÿ3 kg/kWh
3.910ÿ4 kg/kWh
SO2
Fertiliser production
N-fertiliser
Process-related emissions
N2O
NOx
NH3
Energy-related emissionsa
CO2
CH4
N2O
NOx
SO2
IPCC, 1997; Boersema et al., 1986
IPCC, 1997; Boersema et al., 1986
IPCC, 1997; Boersema et al., 1986
Berdowski et al., 1993
0.2 kg PO4-P/kgP
Fertiliser use in rockwool cultivation in greenhouses
N-fertiliser use
N2O
0.01 kg N2O-N/kg N
NOx
0.025 kg NOx-N/kg N
0.1 kg NO3-N/kg N
NO3
P-fertiliser use
PO4
Reference
2.710ÿ2 kg/kg N
1.5810ÿ3 kg/kg N
3.7210ÿ3 kg/kg N
2.5 kg/kg N
2.710ÿ5 kg/kg N
3.7810ÿ5 kg/kg N
8.110ÿ3 kg/kg N
1.1310ÿ2 kg/kg N
IPCC, 1997; McInnes, 1996
IPCC, 1997; McInnes, 1996
IPCC, 1997; McInnes, 1996
IPCC, 1997; McInnes, 1996
IPCC, 1997; McInnes, 1996
Kroeze and Bogdanov, 1997
Biewinga and Van der Bijl, 1996
Biewinga and Van der Bijl, 1996
All emission factors are estimated
from France and Thompson (1993),
IPCC (1997) and McInnes (1996)
(Table continued on next page)
174
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
Table 4 (continued)
Activity
Value
Reference
P-fertiliser
Process-related emissions
NOx
P
Energy-related emissionsb
CO2
CH4
N2O
NOx
SO2
1.5310ÿ3 kg/kg P
4.010ÿ3 kg/kg P
Hoogenkamp, 1992
Bùckman et al., 1990
0.705 kg/kg P
7.610ÿ6 kg/kg P
1.0610ÿ5 kg/kg P
2.2810ÿ3 kg/kg P
3.1810ÿ3 kg/kg P
All emission factors are estimated
from France and Thompson (1993),
IPCC (1997) and McInnes (1996)
Biocide production
Energy-related emissionsc
CO2
CH4
N2O
NOx
SO2
4.77 kg/kg active ingredient
5.1510ÿ5 kg/kg active ingredient
7.210ÿ5 kg/kg active ingredient
1.5010ÿ2 kg/kg active ingredient
2.1510ÿ2 kg/kg active ingredient
All emission factors are estimated
from France and Thompson (1993),
IPCC (1997) and McInnes (1996)
Rockwool production
CO2
SO2
NOx
NH3
0.168 kg/kg rockwool
1.9210ÿ3 kg/kg rockwool
0.02 kg/kg rockwool
1.210ÿ3 kg/kg rockwool
Kaskens et al.,
Kaskens et al.,
Kaskens et al.,
Kaskens et al.,
1992
1992
1992
1992
a
Energy-related emissions from N-fertiliser production are based on an energy use of 27 MJ/kg N
(Melman et al.,1994).
b
Energy-related emissions from P-fertiliser production are based on an energy use of 7.6 MJ/kg P
(France and Thompson, 1993; Melman et al., 1994).
c
Energy-related emissions from biocide production are based on an energy use of 51.5 MJ/kg active
ingredient (Melman et al., 1994).
other (Poppe et al., 1995), we estimated total fertiliser use in these two cultivations
(soil and rockwool cultivation).
2.4. Data for Total Agriculture
The estimated emissions from the Total Agricultural sector are mainly based on
studies by the National Institute for Public Health and the Environment (RIVM)
(Van der Hoek, 1994; RIVM, 1996, 1997; Spakman et al., 1997). In some cases the
estimated emissions are based on additional assumptions.
RIVM uses a de®nition for agriculture that is almost identical to System A
described here. The only exception is indirect emissions of N2O from soils, that
RIVM assigns to agriculture (our System A) but are assigned to System A+I in the
present study. The System A estimates for greenhouse gases, acidifying gases and
eutrophying compounds are mostly based on RIVM studies (Kroeze, 1994; Van der
Hoek, 1994; RIVM, 1996; Spakman et al., 1997). The only additional assumption
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
175
Table 5
Classi®cation factors used in Eq. (2) for emissions of greenhouse gases (in CO2-equivalents), acidifying
gases (in SO2-equivalents) and eutrophying compounds (in PO4-equivalents)
Environmental theme
Compounds
Classi®cation factor
References/notes
Global warming
CO2
CH4
N2O
1 kg=1 CO2-eq
1 kg=21 CO2-eq
1 kg=310 CO2-eq
Over 100 years: from IPCC, 1997
Acidi®cation
SO2
NOxa
NH3
1 kg=1 SO2-eq
1 kg=0.7 SO2-eq
1 kg=1.88 SO2-eq
From Heijungs et al., 1992
Eutrophication
NOxa
NH3
NO3
N
PO4
P
1
1
1
1
1
1
From Heijungs et al., 1992
a
kg=0.13 PO4-eq
kg=0.35 PO4-eq
kg=0.10 PO4-eq
kg=0.42 PO4-eq
kg=1 PO4-eq
kg=3.06 PO4-eq
NOx=mainly/average NO2.
for System A is that 2.5% of the fertiliser N use is emitted as NOx, while total fertiliser N use in The Netherlands was 412 kt N in 1990 (Kroeze, 1994).
The emissions for System I include emissions released during the activities of the
production of electricity, fertilisers, biocides and rockwool (Table 3 lists the associated activity levels). The emission factors associated with these activities in System
I are the same as for Tomato Cultivation and Greenhouse Horticulture (Table 4).
3. Results
The estimated emissions related to speci®c activities within System A and System I
for the three aggregation levels are presented in Table 6. The emissions are expressed
in kg compound as well as in CO2-equivalents (CO2-eq), SO2-equivalents (SO2-eq)
and PO4-equivalents (PO4-eq).
3.1. Results for sector Tomato Cultivation
Total greenhouse gas emissions from Tomato Cultivation are mainly from System
A (Figs. 2 and 3A). CO2 emissions have by far the highest share in total greenhouse
gas emission of System Tomato Cultivation A+I. CO2 emissions resulting from
combustion of natural gas in System A contribute 90% to the total emission of
greenhouse gases in System A+I. Production of electricity in System I results to the
second highest source of greenhouse gas emissions by CO2 emissions. The emissions
of NOx from System A are about half of total NO2 emissions, but are relatively
small compared to CO2 emissions.
176
Table 6
Results for Systems Tomato Cultivation, Greenhouse Horticulture and Total Agriculture A and I
Tomato Cultivation
Greenhouse Horticulture
Total Agriculture
System A
System I
System A
System I
System A
kton
kton
CO2-eq
kton
kton
CO2-eq
kton
kton
CO2-eq
kton
kton
CO2-eq
Greenhouse gases
CO2
Gas use/fuel use in agriculture
Electricity production
Fertiliser N/P production
Biocide production
Rockwool production
Total
1560
0
0
0
0
1560
1560
0
0
0
0
1560
0
104
5
1
2
111
0
104
5
1
2
111
7672
0
0
0
0
7672
7672
0
0
0
0
7672
0
767
23
3
4
797
0
767
23
3
4
797
8600
0
0
0
0
8600
8600
0
0
0
0
8600
0
1918
1787
28
4
3727
0
1918
1787
28
4
3727
CH4
Gas use/energy use
Manure
Electricity production
Fertiliser N/P production
Biocide production
Total
www.elsevier.com/locate/agsy
Quantifying the environmental impact of
production in agriculture and horticulture in
The Netherlands: which emissions do we need
to consider?
J.C. Pluimers a,*, C. Kroeze a, E.J. Bakker b, H. Challa c,
L. Hordijk a
a
Environmental Systems Analysis Group, Wageningen University, PO Box 9101, 6700 HB Wageningen,
The Netherlands
b
Department of Mathematics, Wageningen University, Wageningen, The Netherlands
c
Department of Agricultural Engineering and Physics, Wageningen University, Wageningen, The Netherlands
Received 18 February 1999; received in revised form 25 July 2000; accepted 25 August 2000
Abstract
This study focuses on the environmental impact of agricultural production. The aim of the
study is to identify the most important sources of greenhouse gases, acidifying and eutrophying compounds in Tomato Cultivation, Greenhouse Horticulture and Total Agriculture in
The Netherlands. Within each of these three sectors we distinguish two systems. The System
Agriculture (System A) includes the ®rst-order processes of the agricultural production chain
and the System Industry (System I) includes some second-order processes. Results indicate
that, in general, System A emissions exceed System I emissions. However, in some cases
emissions from System I are relatively high compared to System A emissions, and need to be
considered when quantifying the total environmental impact of agricultural production. For
example, acidifying emissions from the production of electricity and rockwool (both secondorder processes) contribute almost 25% to the total acidifying emissions from System
Greenhouse Horticulture A+I. # 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Environmental systems analysis; Agriculture; Protected cultivation
* Corresponding author.
0308-521X/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved.
PII: S0308-521X(00)00046-9
168
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
1. Introduction
Agricultural production in The Netherlands contributes to various environmental problems. Well-known environmental problems due to agriculture are often
related to speci®c activities and sectors. Dutch greenhouse horticulture, for example, is associated with relatively large emissions of the greenhouse gas carbon
dioxide (CO2) resulting from the combustion of natural gas. At the level of the
total agricultural sector, on the other hand, the emissions of acidifying ammonia
from animal waste are usually considered a major contributor to environmental
problems.
Several studies have been published on the environmental impact of agricultural
production in The Netherlands. These studies dier in their choice of system
boundaries. Sometimes system boundaries are related to economic sectors at a
national scale (e.g. RIVM, 1997). In this way, emissions from fuel combustion in
farms are assigned to agriculture, while emissions from power plants are assigned to
the energy sector. Other studies on the environmental impact of agriculture focus
on the whole production chain of, for instance, a particular crop by using the
methodology of environmental Life Cycle Assessment (LCA) (Nienhuis and de
Vreede, 1994a, b; Wegener Sleeswijk et al., 1996). LCA is a tool for assessing the
environmental impact of a product (Heijungs et al., 1992). Characteristic for LCA is
that it aims to cover the entire life cycle from cradle to grave and to include all
relevant environmental problems related to the product analysed.
Formulation of system boundaries is part of the ®rst step in environmental systems analysis (Table 1) (Checkland, 1979; Wilson, 1984). Usually, environmental
systems analysis deals with policymaking and aims at ®nding solutions to complex
problems that arise in society by describing the system and analysing alternatives
to the system. When de®ning system boundaries, one needs to take into account
spatial as well as temporal aspects. The de®nition of system boundaries partly
depends on the focus and purpose of the study. When studying an economic sector, one may chose to de®ne sub-sectors to describe the most important aspects of
a heterogeneous sector. Temporal boundaries indicate whether the analysis focuses
Table 1
The methodology of systems analysis in six steps as described by Wilson (1984) and Checkland (1979)
Step 1 In the ®rst step the problem is de®ned. The system boundaries, level of aggregation and input
output relations are described
Step 2 In the second step the objectives of the analysis are clari®ed and the model demands are
appointed
Step 3 During the third step the system synthesised, i.e. a model is built, system functions are listed and
alternatives to the current situation are collected
Step 4 The system is analysed by using the model developed in the third step. Uncertainties are
deduced and the performance is compared with the objectives
Step 5 In the ®fth step the optimum system is selected. The decision criteria are described and the
consequences are evaluated
Step 6 During the last step the whole analysis and its conclusions are described
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
169
on the present situation or also includes past or future trends. In this study we
focus on system boundaries within the present horticultural and agricultural
production chain (Fig. 1).
When analysing the emissions of pollutants related to the agricultural sector, ideally, one would aim for a full LCA approach for all products of the agricultural
sector. However, this is not feasible because of the complexity and heterogeneity of
the agricultural sector and the amount of data and time needed for such an analysis.
The question then rises what parts of the production chain have to be described to
analyse a certain environmental problem related to agricultural production, without
performing full LCAs for all products involved; in other words, what are the system
boundaries and how can we decide which inputs, outputs and processes have to be
taken into account and which can be ignored? This study aims at contributing to an
answer to this question.
We focus on three sectoral aggregation levels in this study. Our primary interest is
the analysis of the environmental impact of the greenhouse horticultural sector in The
Netherlands, at a sectoral level resulting in recommendations to policy makers.
The greenhouse horticultural sector is a relatively heterogeneous sector, both in terms
of economic activities and with respect to its environmental impact. Rabbinge and
Van Ittersum (1994) formulated guidelines to cope with tensions between aggregation
levels. They recommend to include the next lower and next higher aggregation level
Fig. 1. Overview of System A(gricultural production) and System A+I(ndustry) and the three aggregation levels: sector Tomato Cultivation, sector Greenhouse Horticulture and sector Total Agriculture.
170
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
in systems analysis in order to determine the relation between the aggregation
levels. In our study we therefore will analyse system boundaries for Greenhouse
Horticulture (primary focus), Tomato Cultivation (a level lower) and Total Agriculture (a level higher).
The aim of this study is to identify the most important present-day emissions of
greenhouse gases, acidifying compounds and eutrophying compounds related to
agricultural production in The Netherlands. For this purpose we will estimate
emissions resulting from activities within the agricultural sector (i.e. ®rst-order processes) as well as answer the question whether emissions due to the production of
most important inputs for the agricultural sector, such as fertilisers, biocides and
electricity (second-order processes) need to be taken into account. We will include
the most important greenhouse gases [carbon dioxide (CO2), methane (CH4)
and nitrous oxide (N2O)], acidifying compounds [sulphur dioxide (SO2), nitrogen
oxide (NOx) and ammonia (NH3)], and eutrophying compounds [nitrogen (N) and
phosphorus (P)].
2. Methodology
In this section we ®rst describe the dierent systems included in the analysis (system de®nition). Next, the method for calculating the emissions (calculation of emissions and environmental impact) is presented and we list the source of emission data
or data used for the calculation of the emissions (data collection).
2.1. System de®nition: System A and System A+I
The agricultural sector is studied here at three dierent aggregation levels
(Tomato Cultivation, Greenhouse Horticulture, Total Agriculture). At each of
these levels two dierent systems are distinguished: System Agriculture and System Agriculture+Industry (Table 2, Fig. 1). Basically, System A (Agriculture) includes the inputs and outputs of the agricultural production system in a
strict sense (®rst-order processes). System I (Industry) includes the production
of electricity, fertilisers, biocides and rockwool, which we consider second-order
processes. The inputs and outputs of System A consist of direct production factors,
respectively, emissions resulting from the use of these direct production factors which include fossil fuels, fertilisers, biocides and rockwool. The inputs to
System I include indirect production factors while the output consists of fertilisers,
biocides, rockwool and electricity produced and the related emissions. Thus in
total we will consider six systems: System Tomato Cultivation A and A+I, System Greenhouse Horticulture A and A+I, and System Total Agriculture A
and A+I (Table 2). We will also quantify indirect N2O emissions as result from
N use in agriculture. These emissions are described in the IPCC emission calculation method (IPCC, 1997) and it is known that these N2O emissions account for
about one-third of the total agricultural N2O emissions worldwide (Mosier et al.,
1998).
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
171
Table 2
Description of the systems studied: System Tomato Cultivation Agriculture (A) and Agriculture and
Industry (A+I), System Greenhouse Horticulture A and A+I and System Agriculture A and A+I
System A
Tomato Cultivation
Greenhouse Horticulture Total Agriculture
Environmental impact
from use of gas, fertilisers,
biocides and rockwool
As Tomato Cultivation,
but Greenhouse
Horticulture includes
both soil and rockwool
cultivation
As Tomato Cultivation
System A+I As System A but including
the environmental impact
of the production of
electricity, fertilisers, biocides
and rockwool (System Industry)
Environmental impact from
fuel use and co-generation
in farms, soils and stables
As System A but including
the environmental impact
of the production of
electricity, fertilisers, biocides
and rockwool (System
Industry)
2.2. Calculation of emissions and environmental impact
We analysed the emissions of CO2, CH4 and N2O (greenhouse gases), SO2 (acidifying gas), NOx and NH3 (acidifying gases and eutrophying gases), NO3 and PO4
(eutrophying compounds). Most of the emissions are either estimated by using
emission inventory data from literature or calculated as a function of agricultural
activities and some emission factors (Tables 3 and 4):
EMISSION f ACTIVITY; EMISSION FACTOR
1
Activities in System A include use of energy, biocides and fertilisers (N and P). In
System A also the production of manure and processes resulting in NH3 emissions
from stables are included. System I describes the production of electricity, fertilisers,
biocides and rockwool.
For each of the compounds considered, the integrated impact of emissions is calculated as (Heijungs et al., 1992) (Table 5):
IMPACT EMISSION CLASSIFICATION FACTOR
2
In this analysis we use as classi®cation factors the Global Warming Potentials
(GWPs) de®ned by the IPCC (1997), and acidi®cation and eutrophication potentials
as described by Heijungs et al. (1992) (Table 5). The GWP is an index of cumulative
radiative forcing between the present and some chosen later time horizon caused by
a unit mass of gas emitted now, expressed relative to the reference gas CO2 (1 kg
CO2) (Houghton et al., 1995). Heijungs et al. (1992) describe classi®cation factors
for substances contributing to acidi®cation and eutrophication expressed in SO2equivalents and PO4-equivalents, respectively.
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J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
Table 3
Activity data for the calculation of the emissions from Tomato Cultivation, Greenhouse Horticulture and
Total Agriculture in The Netherlands as used in Eq. (1)
Activity
Value
Reference
Tomato Cultivation
Gas use
Electricity use
Fertiliser N use
Fertiliser P use
Rockwool use
Biocide use
8.79108 m3
1.25108 kWh
1733 ton N
409 ton P
12.8 kton
11.3 ton
KWIN, 1993
Nienhuis and de Vreede, 1994a
Nienhuis and de Vreede, 1994a
Nienhuis and de Vreede, 1994a
Van der Berg and Lankreijer, 1994; CBS, 1996
CBS, 1996, 1997b
Greenhouse Horticultureb
Gas use
Electricity use
Fertiliser N use in soil cultivation
Fertiliser N use in rockwool cultivation
Fertiliser P use in soil cultivation
Fertiliser P use in rockwool cultivation
Rockwool use
Biocide use
4.3109 m3
9.2108 kWh
4259 ton N
4500 ton N
868.6 ton P
924.9 ton P
25.2 kton
704 ton
Van der Velden et al., 1995
Van der Velden et al., 1995
Poppe et al., 1995, CBS, 1996
Poppe et al., 1995, CBS, 1996
Poppe et al., 1995, CBS, 1996
Poppe et al., 1995, CBS, 1996
IKC, 1995
Poppe et al., 1995
Total Agriculturec
Electricity use
Fertiliser use N
Fertiliser use P
Biocide use
Rockwool use
9 PJ
412 kton N
60 kton P
5812 ton
25 200 ton
CBS, 1997a
Kroeze, 1994
CBS, 1997a
CBS, 1997b
IKC, 1995; CBS, 1996
a
a
b
c
Area sector Tomato Cultivation is 1505 ha (CBS, 1996).
Area sector Greenhouse Horticulture is 10 144 ha (CBS, 1996).
Area sector Total Agriculture is 2106 ha (Kroeze, 1994).
2.3. Data for Tomato Cultivation and Greenhouse Horticulture
The emissions from Tomato Cultivation and Greenhouse Horticulture are estimated following Eq. (1). This requires input data on activities and related emission
factors. These data are listed in Tables 3 and 4, respectively.
For the production of fertilisers and biocides (both activities in System I) we distinguished between energy-related and process-related emissions (Table 4). Processrelated emissions are released during the chemical production process. Energy-related emissions are related to the production of energy used in the chemical process.
We assumed that all electricity used in the production of fertilisers and biocides is
produced by a coal-®red power plant and thus we used the same emission factors as
for electricity production (Table 4). This assumption can be considered a worst case
scenario, because in practice electricity is produced from a mix of fuels.
For Greenhouse Horticulture we distinguished between soil and rockwool cultivation. Based on the area of vegetables, ornamentals, soil and rockwool cultivation
(CBS, 1996) on the one hand and fertiliser use in vegetables and ornamentals on the
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
173
Table 4
Emission factors as used in Eq. (1) for the calculation of the emissions from Tomato Cultivation, Greenhouse Horticulture and Total Agriculture in The Netherlands
Activity
Emission factor
Emission factors related to activities in System A
Gas use
CO2
1.776 kg/m3 natural gas
N2O
7.2010ÿ5 kg/m3 natural gas
NOx
1.4210ÿ3 kg/m3 natural gas
9.510ÿ5 kg/m3 natural gas
CH4
Fertiliser use in soil cultivation in greenhouses
N-fertiliser use
N2O
0.03 kg N2O-N/kg N
NOx
0.025 kg NOx-N/kg N
0.35 kg NO3-N/kg N
NO3
P-fertiliser use
PO4
All emission factors are estimated
from the studies of Mosier et al.
(1998), Daum and Schenk (1996),
Sonneveld (1993) and Postma (1996)
All emission factors are estimated
from the studies of Mosier et al.
(1998), Daum and Schenk (1996),
Sonneveld (1993) and Postma (1996)
0.1 kg PO4-P/kgP
Emission factors related to activities in System I
Electricity production
CO2
0.834 kg/kWh
CH4
9.010ÿ6 kg/kWh
N2O
1.2610ÿ5 kg/kWh
NOx
1.3510ÿ3 kg/kWh
3.910ÿ4 kg/kWh
SO2
Fertiliser production
N-fertiliser
Process-related emissions
N2O
NOx
NH3
Energy-related emissionsa
CO2
CH4
N2O
NOx
SO2
IPCC, 1997; Boersema et al., 1986
IPCC, 1997; Boersema et al., 1986
IPCC, 1997; Boersema et al., 1986
Berdowski et al., 1993
0.2 kg PO4-P/kgP
Fertiliser use in rockwool cultivation in greenhouses
N-fertiliser use
N2O
0.01 kg N2O-N/kg N
NOx
0.025 kg NOx-N/kg N
0.1 kg NO3-N/kg N
NO3
P-fertiliser use
PO4
Reference
2.710ÿ2 kg/kg N
1.5810ÿ3 kg/kg N
3.7210ÿ3 kg/kg N
2.5 kg/kg N
2.710ÿ5 kg/kg N
3.7810ÿ5 kg/kg N
8.110ÿ3 kg/kg N
1.1310ÿ2 kg/kg N
IPCC, 1997; McInnes, 1996
IPCC, 1997; McInnes, 1996
IPCC, 1997; McInnes, 1996
IPCC, 1997; McInnes, 1996
IPCC, 1997; McInnes, 1996
Kroeze and Bogdanov, 1997
Biewinga and Van der Bijl, 1996
Biewinga and Van der Bijl, 1996
All emission factors are estimated
from France and Thompson (1993),
IPCC (1997) and McInnes (1996)
(Table continued on next page)
174
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
Table 4 (continued)
Activity
Value
Reference
P-fertiliser
Process-related emissions
NOx
P
Energy-related emissionsb
CO2
CH4
N2O
NOx
SO2
1.5310ÿ3 kg/kg P
4.010ÿ3 kg/kg P
Hoogenkamp, 1992
Bùckman et al., 1990
0.705 kg/kg P
7.610ÿ6 kg/kg P
1.0610ÿ5 kg/kg P
2.2810ÿ3 kg/kg P
3.1810ÿ3 kg/kg P
All emission factors are estimated
from France and Thompson (1993),
IPCC (1997) and McInnes (1996)
Biocide production
Energy-related emissionsc
CO2
CH4
N2O
NOx
SO2
4.77 kg/kg active ingredient
5.1510ÿ5 kg/kg active ingredient
7.210ÿ5 kg/kg active ingredient
1.5010ÿ2 kg/kg active ingredient
2.1510ÿ2 kg/kg active ingredient
All emission factors are estimated
from France and Thompson (1993),
IPCC (1997) and McInnes (1996)
Rockwool production
CO2
SO2
NOx
NH3
0.168 kg/kg rockwool
1.9210ÿ3 kg/kg rockwool
0.02 kg/kg rockwool
1.210ÿ3 kg/kg rockwool
Kaskens et al.,
Kaskens et al.,
Kaskens et al.,
Kaskens et al.,
1992
1992
1992
1992
a
Energy-related emissions from N-fertiliser production are based on an energy use of 27 MJ/kg N
(Melman et al.,1994).
b
Energy-related emissions from P-fertiliser production are based on an energy use of 7.6 MJ/kg P
(France and Thompson, 1993; Melman et al., 1994).
c
Energy-related emissions from biocide production are based on an energy use of 51.5 MJ/kg active
ingredient (Melman et al., 1994).
other (Poppe et al., 1995), we estimated total fertiliser use in these two cultivations
(soil and rockwool cultivation).
2.4. Data for Total Agriculture
The estimated emissions from the Total Agricultural sector are mainly based on
studies by the National Institute for Public Health and the Environment (RIVM)
(Van der Hoek, 1994; RIVM, 1996, 1997; Spakman et al., 1997). In some cases the
estimated emissions are based on additional assumptions.
RIVM uses a de®nition for agriculture that is almost identical to System A
described here. The only exception is indirect emissions of N2O from soils, that
RIVM assigns to agriculture (our System A) but are assigned to System A+I in the
present study. The System A estimates for greenhouse gases, acidifying gases and
eutrophying compounds are mostly based on RIVM studies (Kroeze, 1994; Van der
Hoek, 1994; RIVM, 1996; Spakman et al., 1997). The only additional assumption
J.C. Pluimers et al. / Agricultural Systems 66 (2000) 167±189
175
Table 5
Classi®cation factors used in Eq. (2) for emissions of greenhouse gases (in CO2-equivalents), acidifying
gases (in SO2-equivalents) and eutrophying compounds (in PO4-equivalents)
Environmental theme
Compounds
Classi®cation factor
References/notes
Global warming
CO2
CH4
N2O
1 kg=1 CO2-eq
1 kg=21 CO2-eq
1 kg=310 CO2-eq
Over 100 years: from IPCC, 1997
Acidi®cation
SO2
NOxa
NH3
1 kg=1 SO2-eq
1 kg=0.7 SO2-eq
1 kg=1.88 SO2-eq
From Heijungs et al., 1992
Eutrophication
NOxa
NH3
NO3
N
PO4
P
1
1
1
1
1
1
From Heijungs et al., 1992
a
kg=0.13 PO4-eq
kg=0.35 PO4-eq
kg=0.10 PO4-eq
kg=0.42 PO4-eq
kg=1 PO4-eq
kg=3.06 PO4-eq
NOx=mainly/average NO2.
for System A is that 2.5% of the fertiliser N use is emitted as NOx, while total fertiliser N use in The Netherlands was 412 kt N in 1990 (Kroeze, 1994).
The emissions for System I include emissions released during the activities of the
production of electricity, fertilisers, biocides and rockwool (Table 3 lists the associated activity levels). The emission factors associated with these activities in System
I are the same as for Tomato Cultivation and Greenhouse Horticulture (Table 4).
3. Results
The estimated emissions related to speci®c activities within System A and System I
for the three aggregation levels are presented in Table 6. The emissions are expressed
in kg compound as well as in CO2-equivalents (CO2-eq), SO2-equivalents (SO2-eq)
and PO4-equivalents (PO4-eq).
3.1. Results for sector Tomato Cultivation
Total greenhouse gas emissions from Tomato Cultivation are mainly from System
A (Figs. 2 and 3A). CO2 emissions have by far the highest share in total greenhouse
gas emission of System Tomato Cultivation A+I. CO2 emissions resulting from
combustion of natural gas in System A contribute 90% to the total emission of
greenhouse gases in System A+I. Production of electricity in System I results to the
second highest source of greenhouse gas emissions by CO2 emissions. The emissions
of NOx from System A are about half of total NO2 emissions, but are relatively
small compared to CO2 emissions.
176
Table 6
Results for Systems Tomato Cultivation, Greenhouse Horticulture and Total Agriculture A and I
Tomato Cultivation
Greenhouse Horticulture
Total Agriculture
System A
System I
System A
System I
System A
kton
kton
CO2-eq
kton
kton
CO2-eq
kton
kton
CO2-eq
kton
kton
CO2-eq
Greenhouse gases
CO2
Gas use/fuel use in agriculture
Electricity production
Fertiliser N/P production
Biocide production
Rockwool production
Total
1560
0
0
0
0
1560
1560
0
0
0
0
1560
0
104
5
1
2
111
0
104
5
1
2
111
7672
0
0
0
0
7672
7672
0
0
0
0
7672
0
767
23
3
4
797
0
767
23
3
4
797
8600
0
0
0
0
8600
8600
0
0
0
0
8600
0
1918
1787
28
4
3727
0
1918
1787
28
4
3727
CH4
Gas use/energy use
Manure
Electricity production
Fertiliser N/P production
Biocide production
Total