1 Introduction
2 Methods
2.1 Contextual background of the models
Climate | PEF | SALCA | Daisy | Animo |
---|---|---|---|---|
Tropical/megathermal | Y* | N | N | Pinto (2016) |
Dry (desert and semiarid) | Y* | N | Manevski et al. (2016) | Farmaha (2014) |
Temperate/mesothermal | Y* | Nemecek et al. (2006) | Mueller et al. (1997) | Rijtema and Kroes (1991) |
Continental/microthermal | Y* | N | Pohanková et al. (2015) | Marinov et al. (2005) |
Polar | Y* | N | N | N |
Extreme weather conditions | Y* | N | N | Hendriks and Akker (2017) |
2.2 Introduction to the N cycle and its adaptation in the models
Parameter | PEF | SALCA | Daisy | Animo |
---|---|---|---|---|
Nitrogen fixation | x | |||
Decomposition | x | x | ||
Immobilization/mineralization | x | x | x | |
Nitrification | x | x | x | |
Atmospheric deposition | x | x | ||
Ammonium leaching | x | x | ||
Ammonium adsorption/desorption | x | x | ||
Plant uptake | x | x | x | |
Nitrate leaching | x | x | x | x |
Denitrification | x | x | x | |
Volatilization | x | x | x | x |
2.3 Description of the models and applied comparison metrics
Criteria | Description and scoring | |
---|---|---|
Completeness of the model scope | ||
Geographic coverage | 1 = Local; 3 = Regional; 5 = Global | |
Environmental relevance | ||
Spatial-temporal resolution | Temporal resolution of the input | 1 = Annual; 3 = Seasonal; 5 = Monthly or higher resolution |
Spatial resolution of the input | 1 = Global; 3 = Regional/National; 5 = Municipality/farmer scale | |
Scientific robustness | ||
Transparency | 1 = No clear modelling explanation, not easily understood; 3 = Processes are clearly modelled but not easily understood; 5 = Processes are clearly modelled and easily understood | |
Input data set/data requirements | 1 = Extensive and detailed input parameters needed; 3 = Application of a questionnaire in a farm, a simple dataset for meteorological and soil physical parameters; 5 = Small and basic parameter input, data obtained global databases or literature | |
Emission model peer-review and (peers) acceptance | 1 = No (unpublished report); 3 = Partially (book or authoritative body report with some review process, or partial publication in a journal, including all parts of the model); 5 = Yes (full peer-reviewed journal for all aspects of the model) | |
The model reflects up-to-date knowledge for the cause-effect chain | 1 = not up-to-date; 3 = partially up-to-date; 5 = yes (state-of-the-art) | |
Tests of the emissions already conducted | 1 = No; 3 = Tested for relevant products/scale and conditions but showing important limitations; 5 = Tested for relevant products/scale, different conditions, peer-reviewed and showing not relevant model limitations | |
Uncertainty and sensitivity analysis | 1 = No; 3 = Yes, but just for the outputs; 5 = Yes, including inputs and outputs | |
Availability, documentation, transparency and reproducibility | ||
Accessibility of the emission model | 1 = No free access/availability; 3 = Available under conditions/on request; 5 = Free access/Internet download | |
Accessibility of the model documentation | 1 = Not accessible; 3 = Accessible with limitations (e.g. fee due, not available in the English language); 5 = Totally accessible | |
Accessibility of the input data | 1 = High limitations (many input data not available in global databases, also data not related to common in LCA). 3 = Low limitations (some data too specific and not available in regional database). 5 = Totally accessible, all data are relatively easy to obtain | |
Modelling assumptions and value choices | 1 = Not described; 3 = Unclear/partial description; 5 = Comprehensive description | |
Completeness of the emission model documentation | 1 = Very incomplete or no documentation; 3 = Partially comprehensive documentation; 5 = Fully comprehensive documentation | |
Applicability and flexibility | ||
Compatibility with LCA methodology | 1 = Not compatible; 3 = Not developed for LCIA but it fits the scope; 5 = Developed for LCA and tested | |
Usability of models for LCA practitioners | 1 = Not used; 3 = Already used but in few situations; 5 = Already used in several studies | |
Related to IPCC TIER concept | 1 = Tier; 3 = Tier 2; 5 = Tier 3 | |
Management operations consideration | 1 = No; 3 = Partially includes; 5 = Totally includes | |
Flexibility (Is it to change parameters and conditions in the model?) | 1 = The model is static: no changes are possible; 3 = Change of conditions and (dis)aggregation of sources are possible; 5 = The model can be easily adapted to new conditions, and aggregation/disaggregation of sources is possible | |
Stakeholder acceptance | ||
Model and model results | 1 = Both difficult to understand; 3 = One of them is difficult to understand; 5 = Both easily understandable | |
Authoritative body behind the model | 1 = No; 3 = Yes, by one of several national bodies; 5 = Yes, endorsed by multinational bodies | |
Academic authority behind the model | 1 = Individual research; 3 = Well trusted on national body; 5 = Well trusted on international body | |
Neutrality across industries, products, or processes | 1 = Yes; 3 = Partially; 5 = No |
2.4 Case study: maize crop in Spain
Geographic parameters | ||
---|---|---|
Location | La Tallada d’Empordà, Girona | |
Coordinates | l: N42.08°L: E03.06 | |
Climate | Arid | |
Soil type | - | Loam |
Soil depth | m | 0.7 |
Clay | % | 18 |
Silt | % | 48 |
Sand | % | 34 |
Organic matter | % | 2.5 |
Soil pH | - | 8 |
Content N in irrigation water | kg \({\mathrm{NO}}_{3}^{-}\)/m3 | 0.009 |
Crop data | ||
Moorish maize yield | t DM ha−1 | 20.65 |
Fertilization | ||
Total calcium ammonium nitrate (CAN) applied | kg N ha−1 | 170* |
PEF | SALCA | Daisy | Animo | |
---|---|---|---|---|
Weather data | - None | - Average monthly precipitation | - Main characteristics of the weather station - Typical max and min temperature in a year - Dry deposition of NH4+ and \({\mathrm{NO}}_{3}^{-}\) - [NH4+] and [\({\mathrm{NO}}_{3}^{-}\)] in precipitation - Global radiation (W/m2) - Precipitation (mm/day) - Reference evapotranspiration (mm/day) - Air temp. (°C) (mean) - Air temp. (°C) (max and min only Animo) - Wind Speed (Animo) | |
Soil characteristics | - None | - pH - Slope - N in soil - Coefficient related to rain washing - Leaching coefficient as a function of the slope | - Depth of the horizons, of max rooting, groundwater and existence of drainage For each soil horizon (A, B, C…) - Clay (%), Silt (%) and Sand (%) - Humus (%) - C:N - Bulk density Mualem van Genuchten model: - α and n (shape parameters) - Ksat (saturated hydraulic conductivity cm/d) | |
Fertilizer | - Amount - Type (for NH3 emissions) | - Type and amount - N availability (organic fertilizers) | - Dry matter fraction (%) - Total C fraction (%) - Total N fraction (%) - NH4+-N fraction (%) - NH4+ volatilization (emission fraction) | |
Crops and field management activities | - None | - N uptake (fraction) - N content in the water irrigation | - Type of crop - Date of ploughing, fertilization, sowing, irrigation and harvesting - Information about storage organ (leaf, stem, stub) | |
Average yields (annual) | - None | - None | - Dry matter (ton DM/ha) - Yield (ton/ha) - N content (kg N/ha) |
3 Results
3.1 Comparison under the criteria and sub-criteria proposed by UNFCCC and other authors for adequacy in the LCA studies
Criteria and subcriteria | Models | ||||
---|---|---|---|---|---|
PEF | SALCA | Daisy | Animo | ||
Completeness of the model scope | |||||
Geographic coverage | 5 | 3 | 5 | 5 | |
Environmental relevance | |||||
Spatial-temporal resolution | Temporal resolution of the input | 1 | 5 | 5 | 5 |
Spatial resolution of the input | 1 | 5 | 5 | 5 | |
Scientific robustness | |||||
Transparency | 1 | 5 | 5 | 5 | |
Input data set/data requirements | 5 | 3 | 1 | 1 | |
Emission model peer-review and (peers) acceptance | 3 | 3 | 5 | 5 | |
The model reflects up-to-date knowledge for the cause-effect chain | 3 | 3 | 5 | 5 | |
Tests of the emissions already conducted | 3 | 3 | 5 | 5 | |
Uncertainty analysis | 3 | 1 | 3 | 3 | |
Availability, documentation, transparency and reproducibility | |||||
Accessibility of the emission model | 5 | 5 | 5 | 3 | |
Accessibility of the characterization model documentation | 5 | 3 | 5 | 5 | |
Accessibility of the input data | 5 | 3 | 1 | 1 | |
Modeling assumptions and value choices | 3 | 5 | 5 | 3 | |
Completeness of the emission model documentation | 5 | 3 | 5 | 5 | |
Applicability and flexibility | |||||
Compatibility with LCA methodology | 5 | 5 | 3 | 3 | |
Usability of models for LCA practitioners | 5 | 5 | 3 | 1 | |
Related to IPCC TIER concept | 1 | 3 | 5 | 5 | |
Management operations | 1 | 3 | 5 | 5 | |
Flexibility | 1 | 5 | 3 | 3 | |
Model and model results | 5 | 5 | 3 | 3 | |
Authoritative body | 5 | 1 | 1 | 1 | |
Academic authority | 1 | 3 | 3 | 3 | |
Neutrality across industries, products, or processes | 5 | 5 | 5 | 5 |
3.1.1 ‘Completeness of the model scope’ and ‘Environmental relevance’
3.1.2 ‘Scientific robustness’
3.1.3 ‘Availability, documentation, transparency and reproducibility’
3.1.4 ‘Applicability and Flexibility’
3.2 Quantitative comparison: a case study of maize crop in Spain (temperate/mesothermal climate)
Source | PEF | SALCA | Daisy | Animo | |
---|---|---|---|---|---|
Input (kg N/ha/year) | Fertilizer (mineral fraction) | 170 | 170 | 170 | 170 |
Deposition | - | - | 15.6 | 14.7 | |
Irrigation | - | 8.3 | 6.8 | 6.2 | |
Plant N fixation | - | 0 | 0 | 0 | |
N in soil | - | - | - | - | |
Seed | - | - | 2.0 | - | |
Total input | 170 | 178.3 | 194.4 | 190.9 | |
Output (kg N/ha/year) | Leaching to groundwater (\(\mathrm{N}-{\mathrm{NO}}_{3}^{-}\)) | 17.0 | 18.0 | 19.9 | 43.7 |
Loss to surface water | - | - | 0 | 0 | |
NH3 Volatilization (N-NH3) | 3.4 | 3.7 | 3.4 | 3.6 | |
NO2 | - | 1.2 | - | - | |
Nitrification (N-N2O) | 2.4 | 1.6 | 3.4 | 2.92 | |
Denitrification (N-N2O and N2) | 7.651 | - | 6.7 | 0.7 | |
N uptake | 265.6 | 265.6 | 190.3 | 199.0 | |
Total output | 296.8 | 290.1 | 223.7 | 249.9 | |
Balance | − 126.7 | − 111.8 | − 29.3 | − 59.0 |
3.3 Characterization of impacts in an LCA of maize crop in Spain
N emission | PEF | SALCA | Daisy | Animo | Variation |
---|---|---|---|---|---|
N2O (kg N2O/ha/year) | 3.8 | 2.5 | 5.5 | 4.6 | 54% |
NH3 (kg NH3/ha/year) | 4.1 | 4.5 | 4.1 | 4.4 | 9% |
NO2 (kg NO2/ha/year) | - | 5.3 | - | - | - |
\({\mathrm{NO}}_{3}^{-}\) (kg \({\mathrm{NO}}_{3}^{-}\)/ha/year) | 75.3 | 79.7 | 88.1 | 193.5 | 61% |
Impact category | Unit | PEF | SALCA | Daisy | Animo | Variation |
---|---|---|---|---|---|---|
CC | kg CO2 eq/ton | 2669 | 2073 | 3175 | 2907 | 35% |
PM | kg PM2.5 eq/ton | 4.17 | 4.22 | 4.17 | 4.19 | 1% |
POF | kg NMVOC eq/ton | 8.42 | 12.26 | 8.42 | 8.42 | 31% |
AC | molc H+ eq/ton | 25.60 | 29.62 | 25.60 | 26.51 | 14% |
TE | kg N eq/ton | 97.36 | 118.99 | 97.36 | 101.41 | 18% |
ME | kg N eq/ton | 21.00 | 23.53 | 23.90 | 47.74 | 56% |
4 Discussion
4.1 Comparison of model evaluation results with previous studies
4.2 Comparison of simulation results provided by the models to field observations
N parameter | Observed | PEF | SALCA | Daisy | Animo |
---|---|---|---|---|---|
N uptake (kg N/ha) | 151–3331 | - | 265.60 | 190.30 | 199.10 |
\({\mathrm{NO}}_{3}^{-}\) leaching (NLC) | 0.11–0.372 | 0.10 | 0.11 | 0.12 | 0.26 |
Volatilization (%) | ~ 1.5%3 | 2.0% | 2.2% | 2.0% | 2.1% |
N2O (kg N2O emitted/ha) | 0.53–0.684 | 3.8 | 2.5 | 5.5 | 4.6 |
Denitrification (kgN/ha) | 2.89–23.215 | 7.65 | - | 6.70 | 0.70 |
Within the range | Not within the range | Not applicable |