2.4. Inventory Analysis
This phase consists of collecting data and performing the necessary calculations to determine in quantitative terms all relevant inputs and outputs within the boundaries of the system [
29]. It can be the most time-consuming phase due to the data collection since it is dependent on a good database and the availability of suppliers and customers to cooperate in the investigation [
10].
This study requires a very strict and detailed data quality. That is why all the primary data for production, harvest and post-harvest periods were collected from a regional farm, which possesses 20 ha of cherry trees, but only 14 of those ha were considered, which were the ones in full production.
This type of localized cherry production, due to its characteristics, enjoys a strong reputation and is considered to have economic, agricultural, and gastronomic importance in the region. The production area of this cherry, in which the regional farm is inserted, provides very favorable edaphoclimatic conditions to the development. The existence of many cold hours during the winter, a mild spring, a hilly area that protects from the wind, granite soils and slope shale, coupled with the local producers’ know-how, result in the attributes of this cherry [
30].
The annual cherry production of the farm was 10 tonnes/ha for each of the 14 ha in full production. The study considers the plantation area (5 m × 3 m) per tree, the number of trees per row and the number of rows where operations of the productive system occurred. The study only covers the impacts associated with one cherry production year because a complete study would require data of approximately 20 years to monitor the cherry tree lifecycle, i.e., from the plantation of the cherry tree until the tree removal. As the company was founded 9 years ago, that data was not available. To do this study, the openLCA 1.10.2 software (GreenDelta GmbH, Berlin, Germany) and the ecoinvent 3.5 database and the Life Cycle Impact Assessment (LCIA) method were also used.
However, there are some limitations to the employed tools. OpenLCA is a tool that uses methods and databases downloaded separately from other sources, and the quality of the results strongly depends on which database is used and for what purpose. Another limitation is the necessity for reference or comparison data in the used databases, which often require to be added by the user. Finally, LCIA has also some limitations, such as not every environmental area is referred to by the default method, and only some elementary flow are characterized, thus being difficult to include all their potential impacts.
This LCA study considers operations during the production and post-harvest phases. In the production phase, the operations of pruning, soil maintenance, spraying of plant protection products, irrigation, herbicide and fertilizer applications were considered. The post-harvest phase covers the operations of refrigerated storing, processing, packaging and transportation of the cherry. These limits can be observed in
Figure 1.
2.4.1. Production Phase
The pruning is performed by electric pruning shears, which are connected to lithium batteries that consume 0.144 kWh. On average, a cherry tree in full production takes 5 min to go through maintenance pruning. Therefore, if 1 ha has 666 plants and 1 plant in full production is pruned in 5 min, the pruning lasts 55.5 h/ha.
The soil maintenance is conducted by two techniques: the sown cover crop between the lines and no-till soil maintenance in the lines of the orchard. To do the maintenance by the sown cover crop, a shredder/weeding machine is used, which takes, on average, 4 h/ha, and this operation is conducted two times per year. The no-till soil technique consists of the application of herbicides, specifically glyphosate. The herbicides are applied two times per year by a pulverization spraying machine, and it takes 2 h/ha per application.
The spraying of plant protection products consists on the application of fungicides and insecticides to protect the orchard against plague attacks and diseases. There are 7 applications of these products during the year, where 6 of them are applications of fungicides that occur simultaneously with 3 applications of insecticides. In addition, an application of insecticides is performed separately. Each application of fungicides and insecticides takes 1 h/ha.
The drip irrigation system is used in the analyzed farm because it is a localized system that always maintains the soil with the necessary humidity, generating good yields. The water is distributed in low intensity and high frequency directly in the root zone of the plants through the drippers. The water irrigation system consumes 2028 m3/ha during the year.
The fertilizers sprayed onto the soil are nitrogen, potassium, phosphorus, zinc, sulfur, magnesium, boron and calcium. The application lasts 1 h/ha, and it is made once a year.
2.4.2. Harvest and Post-Harvest Phase
The harvest is manually made by hand, and the harvested cherries are placed in boxes that are transported by 2 or 3 diesel fuel vans to the warehouse, where they are stored, processed and packaged. The warehouse is located between the parcels, which means that the transportation is variable. If the orchard is close to the warehouse, the trip is only a few meters away, and it is conducted by foot. On the other hand, the trip can take 5–10 min by van if the orchard is further away. These trips from the orchard to the warehouse are frequent, making it impossible to concentrate a large production in the field to avoid sun exposure and high temperatures. During the harvesting, the tractor is not used.
The cherries are stored in refrigeration chambers until they are transported to the retailer. Refrigeration plays an important role in preserving the properties of the cherry in the post-harvest phase and maintaining an adequate temperature and relative humidity. The cherry should be stored at temperatures between 0 °C and 4 °C in an atmosphere with relative humidity between 90% and 95% [
31]. The company stores the cherry at temperatures between 2 °C and 3 °C, and the relative humidity is 90%. Therefore, it is possible to verify that the cooling conditions in the company are within the recommended parameters. This phase is very important to preserve the quality and the properties of the cherry.
InovEnergy (2012) includes the energy power consumptions for the cold storage of horticulture products of several companies in the Center region of Portugal. A linear relationship between the energy power consumption and the number of workers and tons of produced products was determined. Considering the company’s data close to very similar to those of specific farm that made part of this study (3 refrigeration chambers, annual production of 435 tons and 4 permanent workers), an energy power consumption of 25 521 kWh was considered for fruit storage at the company, resulting in energy consumption of 58.67 kWh/ton.
Finally, the transportation of the cherries from the warehouse to the retailer is subcontracted and is carried out by a truck that takes 2–3 h to complete the trip of 200–250 km. During the trip, the cherries are transported at temperatures between 2 °C and 5 °C, and the relative humidity of the air is between 80% and 90%, which are conditions very close to the ideal in order to preserve the quality of the product.
2.4.3. Input Flow
An in-depth investigation of the orchard system was performed to collect all the necessary data and identify the most relevant inputs inventories for cherries LCA. Therefore, energy inputs and emissions considered were from the fuel consumed in transport and in the orchard’s machinery, storage in the warehouse due to the refrigeration system, irrigation water and all plant protection products (fungicides and insecticides), herbicides and fertilizers applied in the soil.
To convert all the inputs considered into their respective energy equivalents, expressed in MJ/ha, the coefficients in
Table 1 were used.
All the inputs considered in this cherries LCA are exposed in
Table 2.
2.4.4. Emissions from the Inputs of the Cherries LCA
The fuel consumption for the production phase is difficult to calculate since the power of agricultural machines is very variable, as its consumption. According to IEA [
34], the density of diesel fuel in Portugal is 0.837 kg/L. Therefore, the diesel fuel consumption of agricultural machinery was calculated using this value for a 60 horsepower (hp) tractor. According to Grisso et al. [
35], it is possible to obtain the fuel consumption of the tractor as shown by Equation (1).
where:
Therefore, the fuel consumption of agricultural machinery during the production phase was 199.8697 L/ha.
According to Pereira et al. [
36] and using values of the “EMEP/EEA Air Pollutant Emission Inventory Guidebook 2019” report, the emissions resulting from fuel burning can be calculated using three methods: Tier 1, Tier 2 and Tier 3. Tier 1 is the most basic method because it requires the least amount of information, while Tier 2 is suitable for more complex situations and in countries where specific emission factors are available. Tier 3 is the most complex method and requires access to a much larger amount of information and data. The emissions from fuel burning of agricultural machinery used during the production phase were calculated by Tier 2, as shown in Equation (2) [
37].
where:
Epollutant = Specific emissions for each pollutant (g);
FCfuel category = Fuel consumption for each fuel category (kg);
EFpollutant = Emission factor for each fuel category (g/kg).
The emissions from the transportation of the cherry can be divided into two different parts, one directed for the Light Commercial Vehicles, LCV < 3.5 tons and the other to the Heavy-Duty Vehicles, HDV > 3.5 tons. Emission factors were taken from the report “EMEP/EEA Air Pollutant Emission Inventory Guidebook 2019” considering the category Euro 3 for the LCV (registration of the vehicle between 2000 and 2004) and Euro 6 to HDV (registration of the vehicle after 2014) [
38]. The remaining data for the transportation in the company is shown in
Table 3.
The calculation of the emissions from the transportation of the cherry was made using the Tier 2 of the “EMEP/EEA Air Pollutant Emission Inventory Guidebook 2019” report, as shown by Equation (3) [
38].
where:
Epollutant = Specific emissions for each pollutant (kg or g);
Ma,b,c = Travelled distance by the vehicle, according to the category a and technology c of the vehicle and the fuel category b (km);
Na,b,c = Number of vehicles of the fleet, according to the category a and technology c of the vehicle and the fuel category b;
EFa,b,c = Emission factor according to the category a and technology c of the vehicle and the fuel category b (g/kg).
The energy power consumed in the storage of the cherry is also a source of emissions for the air. According to IEA [
34], for the gross production of electricity and heat for the years 2012–2014, an average emission factor of 0.322 kg CO
2/kWh of energy power consumed considering its respective transmission and distribution was defined. Therefore, these emissions resulting from the storage of the cherry are calculated by Equation (4) [
39].
where:
Eenergy power = CO2 emissions to air from the energy power consumed for the storage of the cherry (kg CO2/ton of produced cherry);
Cenergy power = Energy power consumed for the storage of the cherry (kWh/ton of produced cherry).
In addition to soil emissions, fertilizers are also a source of CO
2 eq into the air. According to Hughes et al. [
40], the emission factor for nitrogen fertilizers is 6.163 kg CO
2 eq/kg of nitrogen fertilizer. Therefore, CO
2 emissions can be calculated by Equation (5).
where:
Enitrogen fertilizer = CO2 emissions to the air from nitrogen fertilizer applied into the soil (kg CO2 eq/ha);
Qnitrogen fertilizer = Quantity of nitrogen fertilizer applied into the soil (kg of nitrogen fertilizer/ha).
The phosphorus fertilizer also emits CO
2 into the air. According to Hughes et al. [
40], the emission factor for phosphorus fertilizer is 1.859 kg CO
2 eq/kg of phosphorus fertilizer. Therefore, CO
2 emissions can be calculated by Equation (6).
where:
Ephosphorus fertilizer = CO2 emissions to the air from phosphorus fertilizer applied into the soil (kg CO2 eq/ha);
Qphosphorus fertilizer = Quantity of phosphorus fertilizer applied into the soil (kg of phosphorus fertilizer/ha).
The potassium fertilizer is also a source of CO
2 emissions to the air. According to Hughes et al. [
40], the emission factor is 1.770 kg CO
2 eq/kg of potassium fertilizer. Therefore, CO
2 emissions can be calculated by Equation (7).
where:
Epotassium fertilizer = CO2 emissions to the air from potassium fertilizer applied into the soil (kg CO2 eq/ha);
Qpotassium fertilizer = Quantity of potassium fertilizer applied into the soil (kg of potassium fertilizer/ha).
In addition to the emissions mentioned before from nitrogen fertilizers, there still are other direct and indirect emissions to the air resulting from that fertilizer. The direct emissions are due to the degradation of organic matter, releasing nitrogen fixed in the soil. These direct impacts, according to the “Portuguese National Inventory Report on Greenhouse Gases, 1990–2017”, can be calculated by Equation (8) [
41]. The nitrogen fertilizer also has indirect N
2O emissions to the air due to the volatilization and atmospheric deposition of the nitrogen applied into the soil. The nitrogen is volatilized in the form of NH
3 and NO
x, and, sometimes, a fraction of that volatilized nitrogen returns to the soil, and it is reemitted as N
2O. Therefore, according to the “Portuguese National Inventory Report on Greenhouse Gases, 1990–2017”, the indirect N
2O emissions resulting from the application of nitrogen fertilizers into the soil can be calculated by Equation (8) [
41].
where:
EdirectN2O = Direct emission from nitrogen fertilizer applied into the soil (kg N2O/ha);
FAS = Quantity of nitrogen fertilizer applied into the soil (kg N/ha);
Value of 0.010 = Emission factor for the emissions of N2O from nitrogen fertilizer applied into the soil (kg N2O-N/kg of nitrogen fertilizer applied into the soil);
Value of 44/28 = Conversion factor from N2O–N emissions to N2O emissions.
The indirect emissions from nitrogen fertilizer applied into the soil was calculated using Equation (9).
where:
N2O(DAT) = Indirect emissions from nitrogen fertilizer applied into the soil (kg N2O/ha);
FAS = Quantity of nitrogen fertilizer applied into the soil (kg N/ha);
0.083 = Fraction of the nitrogen fertilizer that volatiles as NH3 and NOx (kg of volatilized N/kg of N applied into the soil);
0.010 = Emission factor for the emissions of N2O from nitrogen fertilizer applied into the soil (kg N2O–N/kg of nitrogen fertilizer applied into the soil);
44/28 = Conversion factor from N2O-N emissions to N2O emissions.
Fungicides applied into the soil are also a source of GHG emissions to the air. According to [
40], the fungicides emission factor is 3.303 kg CO
2 eq/kg of fungicides. Therefore, CO
2 emissions can be calculated by Equation (10).
where:
Insecticides applied into the soil also emit CO
2 to the air. According to [
40], the insecticides emission factor is 4.744 kg CO
2 eq/kg of insecticides. Therefore, CO
2 emissions can be calculated by Equation (11).
where:
Herbicides applied into the soil are also a source of CO
2 emissions to the air. According to [
40], the herbicides emission factor is 5.076 kg CO
2/kg of herbicides. Therefore, CO
2 emissions can be calculated by Equation (12).
where:
2.4.5. Test Case Scenarios
The annual cherry production is very variable because it depends on the growing season and the climatic conditions, as they can be favorable or not to the development of diseases and plagues. In the agricultural region of Beira Interior (Portugal), the cherry registered substantial falls in production in some growing seasons that varied between approximately 50% (fall registered in 2007) and 60% (fall registered in 2016). These production falls were mainly due to adverse climatic conditions and plague attacks. On the other hand, there are also years, such as in 2011 and 2015, when conditions were favorable, resulting in a total production increase between 25% and 50% [
42].
Therefore, two alternative scenarios were defined with the goal of making an analysis for the low and high cherry production scenarios. In scenario 1, the low production scenario, a decrease of 50% of production, from 10 tons/ha to 5 tons/ha, is considered due to adverse climatic conditions, the attack of plagues and the development of diseases in the orchard. This scenario will necessarily lead to an increase in the number of sprayings of plant protection products. In scenario 2, the high production scenario, an increase of 50% of production (from 10 tons/ha to 15 tons/ha) is considered due to favorable climatic conditions for the growth of the cherry, leading to a decrease in the number of sprayings of plant protection products.
The consumption of agricultural operations during the production phase remains the same in both scenarios because they do not depend on the produced quantity, except for the number of plant protection products sprayings. In the post-harvest phase, the same operations as in the real scenario are considered.