Life-cycle assessment of the soybean-sunflower production system in the Brazilian Cerrado

TLDR: In this paper, the authors performed a life cycle assessment (LCA) of the soybean-sunflower cropping system, identified its hotspots, and compared its environmental performance with two hypothetical monocultures, in order to corroborate its benefits.

Abstract: In the “Cerrado” (Brazilian savanna), sunflower comes mostly from a cropping system where its seeding follows soybean harvest. Soybean has a much higher economic value, but this association with sunflower reduces the environmental impacts from both crops by sharing resources. This study performed a life-cycle assessment (LCA) of the soybean-sunflower cropping system, identified its hotspots, and compared its environmental performance with two hypothetical monocultures, in order to corroborate its benefits. Soybean-sunflower cropping system inventory used data from farms of the Parecis region, consolidated by experts. Inventories for soybean and sunflower monocultures were estimated from the cropping system inventory. LUC (land-use changes) were calculated from CONAB (2015), FAOSTAT (2012), and Macedo et al. (P Natl Acad Sci USA 109:1341–1346, 2012). Emissions estimation followed Nemecek and Schnetzer (2011), Mila i Canals (2003), and EC (2010). Land occupation, land-use changes, and liming were allocated by occupation time, but a sensitivity analysis was performed for yield and gross margin as allocation criteria. ReCiPe Midpoint (H) v1.12/World ReCiPe H was the impact assessment method, and some categories were disregarded as not relevant. We used pedigree matrix to estimate uncertainties for inventory and Monte Carlo method for impact uncertainty analysis as in Goedkoop et al. (2008). We used SimaPro 8.0.5.13. The soybean-sunflower cropping system generate relevant human toxicity, freshwater toxicity, freshwater eutrophication, climate change, and terrestrial acidification impacts, related to emissions derived from nitrogen and phosphate fertilizers and emissions generated by LUC. Sunflower-soybean cropping system has better environmental performance when compared to the combination of monocultures because of a number of synergies made possible by sharing land use and other resources. Changing the allocation criteria altered the relative performance of some categories, but in all categories the environmental impacts of the cropping system were lower than those of the corresponding monoculture impacts, regardless of the allocation criteria implemented. We concluded that the environmental performance of the soybean-sunflower cropping system can be improved by optimizing the use of chemical fertilizers. Climate change impacts, which are mostly driven by LUC, could be reduced by production intensification, preventing the clearing of native vegetation for agricultural purposes. This study confirmed the environmental benefits of cropping systems when compared to monocultures and the advantages of association of nitrogen-fixing legumes with other plant species in a production system.

Figures

Table 1 - Environmental profile of soybean and sunflower crop system and monocultures for 1 ton of crop (allocation criteria: occupation).

Table 3 - Impact on each category allocated to soybean and sunflower in a rotation crop system, calculated using each the three allocation criteria and normalized as a percentage of the impact these crops have in monocultures of the same yield. Important results are commented on the text.

Table 2 shows soybean and sunflower environmental profile in rotation crop system and monoculture by the occupation allocation criterion.

Full text

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Life Cycle Assessment of soybean-sunflower
production system in the Brazilian Cerrado
Marília I. S. Folegatti Matsuura
1
, Fernando R. T. Dias
2
, Juliana F. Picoli
1
,
Kássio R. Garcia Lucas
3
, César de Castro
4
, Marcelo H. Hirakuri
4
1
Embrapa Meio Ambiente,
2
Embrapa Pantanal,
3
Universidade Estadual de
Londrina,
4
Embrapa Soja
1
Tel. +55 19 33112731
marilia.folegatti@embrapa.br, fernando.dias@embrapa.br, picoli.ju@gmail.com,
kassiorgl@hotmail.com, cesar.castro@embrapa.br, marcelo.hirakuri@embrapa.br
Abstract
Sunflower is an important crop in Parecis region of the Brazilian Cerrado. In 2014, the region
produced 232.700 tons of sunflower grains, 45% ofthe national production. Sunflower production
comes mostly from a system that has soybean as the main crop. The association of soybean and
sunflower can reduce environmental impacts due to shared use of resources. This study performed
a “cradle to gate” Life Cycle Assessment (LCA) of the soybean-sunflower production system used
in Parecis region and compared its environmental profile to that of the monoculture of these two
crops. We evaluated the impacts related to the use of soil (land use change emissions and liming)
for each crop according to three allocation criteria: time of soil occupation, yield and gross margin.
Although performance on “Climate Change” and some other impact categories had varied
according to the allocation criteria used, the soybean-sunflower rotation crop system presented
lower environmental impacts on every category when compared to soybean and sunflower
monocultures with the same yield. Important impact reductionswere observed on “Climate
change” (43%), “Terrestrial acidification” (26%) and “Particulate matter formation” (20%)
categories.
Keywords: Environmental Impact Assessment, Environmental Modeling,
Savanna, Rotation Crop Systems, Allocation Criteria.
Introduction
The adoption of new production technologies made it possible for Brazil to stand out as a major
food world supplier, but the search for sustainability is one of many new challenges, as the global
market asks for products with reduced environmental impact (Claudino and Talamini 2013). Life
Cycle Assessment (LCA) is a great tool to assess agricultural product environmental performance.
Due to its adaptability (Rizzardi and Milgiorança 1993), sunflower crop yield in Brazilian Cerrado
has been encouraging. The Parecis region is the "home" of sunflower in Brazil and is accounted

225
for 61 % and 45% of regional and national production, respectively, in the 2013/2014 harvest
(AMM 2014).
Soybean also grow in Parecis region, as monoculture or with sunflower in succession (soybean is a
summer crop and it is not possible to grow two soybean crops in the same year). Soybean is the
crop that has the greatest economic importance to Brazil: its planted area increased by 49% over
the past three decades due to its cultivation in the Brazilian Cerrado, thanks to the development of
agricultural technology adequate to this biome (MAPA 2014). Sunflower cultivation in succession
to soybean can reduce environmental impacts because of the more efficient land use and sharing of
agricultural inputs, machinery and infrastructure. With a LCA study, we can determine this impact
reduction, but we must also identify the correct way to allocate the impacts of soybean-sunflower
production system between its two products, as this can influence the recommendations of a LCA
study.It is noteworthy that we have not found any other LCA study that had evaluated soybean-
sunflower crop systems in the scientific literature.
Methods
This study generated inventories of soybean and sunflower production in monoculture and in
succession based on the representative typical systems of Parecis region. The most relevant items
of the scope of this study are:
a) Reference Unit: 1 ton of grain for each system, with ayield of 3120 kg of soybeans and 1774 kg
of sunflower per hectare for monoculture and rotation crop system.
b) Data Sources: Soybean-sunflower system data obtained by interviewing five producers of the
Parecis region. Information obtained from these interviews, consulting experts and technical
literature allowed us to define the typical soybean-sunflower rotation crop system and monoculture
of these two crops. We calculated emissions from the rotation crop system and monocultures
following Nemecek and Schnetzer (2011) recommendations, except for heavy metal emissions,
that we estimated as proposed by Canals (2003). Data from production of agricultural inputs came
from Ecoinvent v2.2. We excluded transport of agricultural inputs from the analysis. Table 1 show
main inputs and outputs from LCI.

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Products Unit Soybean Sunflower
Product kg 3.12E+03 1.77E+03
Resources
Occupation, arable, non-irrigated ha/year 3.15E-01 3.29E-01
Materials/fuels
Maizeseed kg 4.00E+01 3.50E+00
Lime kg 2.45E+02 2.55E+02
Urea, as N kg -- 4.42E+01
Single superphosphate, as P2O5 kg 7.20E+01 --
Triple superphosphate, as P2O5 kg -- 1.84E+01
Potassiumchloride, as K2O kg 7.80E+01 2.40E+01
Herbicides kg 4.04E+00 2.87E+00
Insecticides kg 5.80E-01 3.02E-01
Fungicides kg 3.56E-01 1.54E-01
Emissionstoair
Ammonia kg -- 1.44E+01
Dinitrogenmonoxide kg 2.64E+00 1.87E+00
Nitrogen oxides kg 5.55E-01 3.92E-01
Carbondioxide, fossil kg -- 6.93E+01
Carbondioxide, landtransformation kg 3.99E+03 4.16E+03
Emissionstowater
Nitrate kg 1.91E+01 2.89E+01
Cadmium kg 2.08E-06 2.09E-07
Copper kg -- 3.88E-07
Zinc kg 1.73E-07 1.81E-06
Lead kg 2.02E-07 4.01E-08
Nickel kg 8.17E-07 1.96E-07
Chromium kg 1.07E-05 1.32E-06
Emissionstosoil
Cadmium kg 2.08E-02 2.09E-03
Copper kg -- 3.88E-03
Zinc kg 1.73E-03 1.81E-02
Lead kg 2.02E-03 4.01E-04
Nickel kg 8.17E-03 1.96E-03
Chromium kg 1.07E-01 1.32E-02
Herbicides kg 4.04E+00 2.87E+00
Insecticides kg 5.80E-01 3.02E-01
Fungicides kg 3.56E-01 1.54E-01
Table 1 - Environmental profile of soybean and sunflower crop system and monocultures for 1 ton
of crop (allocation criteria: occupation).
c) Allocation Procedure: We allocated the impacts from land use change and limestone use in

227
acidity correction according to the time of occupation of the same area by each crop per year (120
days for soybean and 115 days for the sunflower, per year). We also tried two other allocation
criteria, in other to evaluate their influence on the evaluation: yield (3120 kg ha-1 for soybean and
1774 kg ha-1 for sunflower) and gross margin per crop. For the gross margin criterion, impacts
from land use change and limestone use were completely allocated to soybean,because the gross
margin from sunflower is very small when compared to the gross margin from soybean for the
same area. Other impacts from inputs and emissions were attributed to the product accountable for
the input consumption or emission, in all three allocation criteria, as in Nemecek et al. (2001).
d) Method: LUC from 1990 to 2009 for soybean and sunflower cultivation were calculated from
historical series of CONAB (2015), FAOSTAT (2012) and Macedo et al. (2012). Emissions from
LUC were calculated according to EC (2010).We chose the Recipe Midpoint (H) v1.07 / World H
as the life cycle environmental impact assessment method. We disregarded impact categories not
relevant to the study (marine eutrophication,marine ecotoxicity, ionizing radiation, urban land
occupation). SimaPro, version 8.0.4.26, was the software tool used.
Results and Discussion
Table 2 shows soybean and sunflower environmental profile in rotation crop system and
monoculture by the occupation allocation criterion.
Impact Category Unit Soybean
mono
Soybean
crop
Sunflower
mono
Sunflower
crop
Climate change kg CO2 eq 3.09E+03 1.76E+03 5.39E+03 2.99E+03
Ozone depletion kg CFC-11 eq 3.11E-05 3.09E-05 7.67E-05 7.07E-05
Terrestrial acidification kg SO2 eq 2.04E+00 2.04E+00 3.13E+01 2.21E+01
Freshwater eutrophication kg P eq 1.27E-01 1.27E-01 9.53E-02 8.87E-02
Human toxicity kg 1,4-DB eq 7.38E+02 7.38E+02 2.18E+02 2.08E+02
Photochemical oxidant
formation
kg NMVOC 2.12E+00 2.11E+00 2.67E+00 2.53E+00
Particulate matter formation kg PM10 eq 8.49E-01 8.47E-01 4.77E+00 3.52E+00
Terrestrial ecotoxicity kg 1,4-DB eq 1.23E+00 1.23E+00 1.29E-01 1.17E-01
Freshwater ecotoxicity kg 1,4-DB eq 3.70E+00 3.70E+00 2.46E+00 2.32E+00
Agricultural land occupation m2a 6.26E+01 6.26E+01 2.08E+01 2.03E+01
Natural land transformation m2 5.54E-02 5.51E-02 9.76E-02 8.46E-02
Water depletion m3 3.23E+00 3.23E+00 2.12E+00 2.03E+00
Metal depletion kg Fe eq 1.51E+01 1.51E+01 1.78E+01 1.63E+01
Fossil depletion kg oil eq 2.48E-01 2.48E-01 1.81E-01 1.71E-01
Table 2 - Environmental profile of soybean and sunflower crop system and monocultures for 1 ton
of crop (allocation criteria: occupation).
We can see that soybean has lower impact than sunflower in half of the impact categories.
Emissions of carbon dioxide resulting from Land Use Change (LUC) and nitrous oxide emissions
generated by nitrogen fertilizers were the main cause for "Climate change" impacts. For
"Photochemical oxidant formation", "Terrestrial acidification" and "Particulate matter formation"

228
categories, the main contaminants were ammonia and nitrogen oxides, also related to nitrogen
fertilization. In all these categories soybean has better performance than sunflower, for its ability
to fix atmospheric nitrogen, eliminating the contribution of synthetic fertilizers.
For "Human Toxicity" and "Terrestrial and Aquatic Ecotoxicity" categories, soybeans had worse
performance because of impacts caused by emission of heavy metals entering the production
system by limestone, fertilizers, seeds, and pesticides. Soybean needs more seeds (which contain a
large amount of heavy metals) and uses a greater number of pesticides (26 for soybean, 15 for
sunflower) and in a greater quantity. In addition, all three allocation criteria assign to soybean the
major share of environmental load of liming on the production system.
Sunflower produced in a rotation crop system has reduced environmental impact in all categories
when compared to that produced as monoculture, because sunflower benefits from being preceded
by soybean, especially for nitrogen fixation, which contributes about 20 kg of this element per
hectare, reducing the synthetic nitrogen fertilizer application and emissions. Soybean impact had
reduced only for the "Climate Change" category, due to allocation to sunflower of a share of land
use impacts (Table 3).
Soybean in crop system Sunflower in crop system
occupation yield gross
margin
occupation yield gross
margin
Climate change 57%
69%
100%
56%
43%
12%
Ozone depletion 100%
100%
100%
92%
92%
92%
Terrestrial acidification 100%
100%
100%
71%
71%
71%
Freshwater eutrophication 100%
100%
100%
93%
93%
93%
Human toxicity 100%
100%
100%
95%
95%
95%
Photochemical oxidant formation 100%
100%
100%
95%
95%
94%
Particulate matter formation 100%
100%
100%
74%
74%
74%
Terrestrial ecotoxicity 100%
100%
100%
90%
89%
85%
Freshwater ecotoxicity 100%
100%
100%
94%
94%
94%
Agricultural land occupation 100%
100%
100%
98%
98%
98%
Natural land transformation 99%
100%
100%
87%
86%
86%
Water depletion 100%
100%
100%
96%
96%
95%
Metal depletion 100%
100%
100%
91%
91%
91%
Fossil depletion 100%
100%
100%
95%
95%
94%
Table 3 - Impact on each category allocated to soybean and sunflower in a rotation crop system,
calculated using each the three allocation criteria and normalized as a percentage of the impact
these crops have in monocultures of the same yield. Important results are commented on the text.
Our results agree with those obtained by Hayer et al. (2010), who also noted that the inclusion of
legumes could reduce the Global Warming Potential for the reasons herein.
Impactsfrom shared land use change and limestone supply were allocated to soybean and
sunflower by “occupation”, i.e., in proportion to the time that each crop covered the soil in the
rotation crop system. We also tried other two allocation criteria in order to evaluate their possible
effect on a decision between rotation crop system and monoculture for each crop. For soybean,
changing the allocation criteria affected noticeably only the "Climate change" impact category. As

Frequently asked questions

Q1. What have the authors contributed in "Life cycle assessment of soybean-sunflower production system in the brazilian cerrado" ?

This study performed a “ cradle to gate ” Life Cycle Assessment ( LCA ) of the soybean-sunflower production system used in Parecis region and compared its environmental profile to that of the monoculture of these two crops. 

Q2. What are the main causes of the impacts of the soybeans?

Emissions of carbon dioxide resulting from Land Use Change (LUC) and nitrous oxide emissions generated by nitrogen fertilizers were the main cause for "Climate change" impacts. 

Q3. What is the impact of the rotation crop system on soybean?

The categories with greatest impact reduction were "Climate Change", "Terrestrial Acidification" and "Particulate Matter Formation", for which the impact of rotation crop system amounted respectively to 56%, 74% and 80% of the sum of impacts from soybean and sunflower monocultures with the same area and yield. 

Q4. What is the main reason why Brazil is a major food supplier?

Sunflower cultivation in succession to soybean can reduce environmental impacts because of the more efficient land use and sharing of agricultural inputs, machinery and infrastructure. 

Q5. What is the impact of the soybean on the soil?

Soybean needs more seeds (which contain a large amount of heavy metals) and uses a greater number of pesticides (26 for soybean, 15 for sunflower) and in a greater quantity. 

Q6. What is the reason for the large reduction of impacts in this category?

The large reduction of impacts in this category for gross margin allocation criterion is due to the allocation to soybean of the full impact related to land use change and use of limestone, as mentioned on the previous paragraph. 

Q7. What is the relevant item of the scope of this study?

The most relevant items of the scope of this study are: a) Reference Unit: 1 ton of grain for each system, with ayield of 3120 kg of soybeans and 1774 kg of sunflower per hectare for monoculture and rotation crop system. 

Q8. What was the gross margin criterion for soybean?

For the gross margin criterion, impacts from land use change and limestone use were completely allocated to soybean,because the gross margin from sunflower is very small when compared to the gross margin from soybean for the same area. 

Q9. What is the important factor in reducing environmental impacts?

Sunflower-soybean rotation crop system reduced environmental impacts in all categories when compared to the combination of monocultures, because of a number of synergies made possible by sharing land use and other resources. 

Q10. What is the main reason why Brazil has grown soybean?

Soybean is the crop that has the greatest economic importance to Brazil: its planted area increased by 49% over the past three decades due to its cultivation in the Brazilian Cerrado, thanks to the development of agricultural technology adequate to this biome (MAPA 2014). 

Q11. What is the important factor in reducing environmental impacts of cereal-legume system?

The cereal-legume system resulted in lower impacts in all of these categories due to reduced application of nitrogen fertilizer, the expansion of the possibilities of using reduced tillage techniques and the lower incidence of disease problems (due to the diversification of crops). 

Q12. What is the impact of the sunflower monoculture?

For sunflower, the impact category "Climate change" was more affected when the allocation criterion was changed: 56%, 43% and 12% of the sunflower monoculture impact on this category, respectively, for occupation, yield and gross margin. 

Q13. What were the main impacts caused by the emission of heavy metals into the production system?

For "Human Toxicity" and "Terrestrial and Aquatic Ecotoxicity" categories, soybeans had worse performance because of impacts caused by emission of heavy metals entering the production system by limestone, fertilizers, seeds, and pesticides.