2.4.1. Rapeseed Cultivation and Drying
In Latvia, spring rapeseed in the Zemgale region is usually sown in April and harvested 20–28 August. Winter rapeseed is sown between August 5 and 25 and harvested from 28 July to 10 August.
The lead agronomist in the company reported that the typical soil type where rapeseed crop is grown is sandy loam or loam sod-calcareous soil. As reported by [1
], the average organic matter content of the soil is 3.4%, pH is 7.4, and the soil has a normal humidity regime. The company does not lime nor irrigate their fields. The lead agronomist reported that the company uses a specific standard fertilizing scheme for both winter and spring rapeseed. The yearly dosage can change ±10% depending on various factors. The company does not take into account nutrients from the previous crop and the standard fertilizing scheme is not adjusted to this factor. No organic fertilizers were taken into account, as the applied amount and area vary significantly on a year-to-year basis.
The company practices intensive farming utilizing a low-tillage method for winter rapeseed with the adoption of a soil disc cultivation at a depth of a 10–12 cm. After that, the company uses agricultural machinery that carries out soil loosening and sowing in one-step. In the case of spring rapeseed, tillage is used, followed by disc cultivation, drag harrowing, and soil loosening and sowing in one-step.
The inventory data for winter and spring rapeseed are summarized in Table 1
. The data presented in Table 1
must be integrated with the in-depth LCI data already discussed and presented in a paper by [1
]. The previously presented LCI data has to be harmonized with the processes and materials available in the ecoinvent v3.5 database.
The paper used a background of this study [1
], in which the authors reported the application of sulfur and micronutrients on rapeseed cultivation. With reference to FU of this LCA study (1 tonne of produced rapeseed), these amounts are equal to 16.7 and 21.4 kg/t of applied sulfur for winter and spring rapeseed, respectively. For both rapeseed species, micronutrient mixtures in a total of 5.0 L/ha were also applied, which equals to 1.4 and 2.0 L/t for winter and spring rapeseed, respectively. Micronutrients and sulfur constitute approximately 14.0% and 14.1% of the total application of fertilizers for winter and spring rapeseed, respectively. These figures are in line with the outcomes by Schmidt [6
] that show a share of 13% of the total application of fertilizers not including magnesium (Mg), sulfur (S), and boron (B). Unfortunately, no life cycle inventories have been identified for these fertilizers. Therefore, sulfur and micronutrient mixtures are not included in this LCA study. Other authors [6
] also reported that for several fertilizers, such as multi-nutrient compounds S, B, Mg, and others, there are no life cycle inventories. These fertilizers have not been comprehensively assessed and thus these inputs have to be excluded from the LCA or adapted with a generalization of the type of fertilizer used. It was identified that other studies do not report the use of micronutrients for rapeseed production and thus this aspect has not been comprehensively assessed in rapeseed cultivation. Moreover, it is not clear whether crop companies in other countries use micronutrients, because in the vast majority of papers, micronutrient input flow is not reported. According to [8
], most likely all farmers use micronutrients. In Latvia as well as Lithuania, agricultural companies choose to use micronutrients that are foliarly-applied nutrients because they are directly absorbed through the leaves. This uncertainty highlights the need to improve and expand the database of fertilizer and micronutrient inventories.
The total amount of N, P, and K fertilizers equals 117.5 kg/t for winter rapeseed, while for spring rapeseed, this amount rises to 150.8 kg/t. The total amount of applied nitrogen reached 63.2 and 74.8 kg N/t for winter and spring species, respectively, and was satisfied with 4 different fertilizers. In Latvia, many fertilizers are imported from Belorussia, Russia, and Lithuania, and for many of them, there are no inventories present in the ecoinvent v3.5 database, so the assumption has to be made or the closest general data from the inventory has to be selected. Moreover, different fertilizers available in the market present a different share of NPK values and at times contain a portion of sulfur—i.e., NPKS 4-16-34-2S and KAS N25+S3 under the trade name Lyderis© 25 + S3, which is a urea ammonium nitrate mixture with additional sulfur. The in-depth LCI data about fertilizers also has to be harmonized with processes and materials available in the ecoinvent v3.5 database. To model fertilizers, the data from the State Plant Protection Service about the volume of fertilizers produced in and imported into Latvia was used. Fertilizers from Table 1
were modeled as the largest produced and imported fertilizer in the corresponding fertilizer type [9
]. Within the present LCA model, the NPKS 4-16-34-2S fertilizer satisfied the phosphorus and potassium requirements; the input of potassium oxide (K2
O) was modeled as an input of potassium chloride, while the input of phosphorus pentoxide (P2
) was modeled as an input of diammonium phosphate. Nitrogen in the NPKS 4-16-34-2S fertilizer was modeled as an input of ammonium sulfate. Fertilizer KAS N25+S3 is a urea ammonium nitrate mixture that contains 25% of nitrogen and was modeled as urea ammonium nitrate with N content 32%. The amount was recalculated to correspond to the nitrogen content in fertilizer KAS N25+S3.
The study of Fridrihsone et al. (2018) details the use of different plant protection products, their amount, and active ingredients [1
]. The input of plant protection products was aggregated according to their chemical class in the ecoinvent 3.5 database [10
After harvesting, rapeseeds are transported to drying and purification. A drying kiln heated by gas with a drying capacity of 60 t/h is used. Purification takes place through a sieve using gravity and wind power [8
]. Drying is requested by industry actors to avoid spoilage by fungi and mites during storage [11
]. The agricultural company provided data about the amount of gas needed for drying 1 tonne of grain crops (including rapeseed). In this case, it was not divided more finely as the company does not collect such type of data. Depending on the year and amount of precipitation, rapeseed contains a different amount of moisture and the amount of gas required for drying varies significantly. For example, in 2016 during harvesting, there was a lot of rain, the grains had high moisture content, and the needed gas was 9.1 m3
/t. In 2015, the weather was dryer and the natural gas consumption for seed drying was only 1.2 m3
]. On average during 2013–2016, the natural gas consumption for drying 1 tonne of grain crops was 5.9 m3
/t. The lower heating value of 31.82 MJ/m3
was taken from official data provided by the natural gas provider in Latvia [12
], which resulted in 189.2 MJ per tonne of rapeseed. Other studies report various values for grain drying in terms of MJ; for example, French researchers report 147.9 MJ/t provided with electricity [13
], whereas for rapeseed cultivated in Poland, only 17.1 MJ/t is reported for grain drying [14
] provided with fuel oil. A German study reported 420 MJ/t provided with electricity and fuel oil [15
]. The amount of evaporated water is calculated according to the methodology described by Nemecek and Kagi, 2007 [10
]. Rapeseed is dried until the moisture content of 8%; the moisture content after harvest on average is 12% [8
Emissions to air, water, and soil are caused by the use of fertilizers and plant protection products. The emissions of plant protection products to the soil and surface water are estimated at 50% and 0.50% of the applied active ingredient, with the difference being exported or destroyed under climatic conditions [17
]. For phosphorus, the phosphate leaching was specified as 2.9% of the surplus of phosphorus [1
]. The rest is accumulated into the soil. For winter rapeseed, the emissions of phosphorus (0.04 kg/t) correlate with the value (0.04 kg/t) reported by Schmidt, 2007. Nitrate leaching was calculated from the applied N amount on the field reported previously; the default IPPC default leaching fraction of 0.3. was taken [18
]. The detailed conditions and the sources utilized to calculate the emissions of plant protection products to the air are described in the LCI study by Fridrihsone et al. (2018) [1
]. The use of nitrogen fertilizers is of great concern and has been acknowledged as an important environmental impact in rapeseed cultivation. The use of nitrogen fertilizers contributes significantly to the nitrous oxide emissions from soils [19
]. Nitrous oxide emissions from the cultivation of winter and spring rapeseed were calculated using the Global Nitrous Oxide Calculator (GNOC)—an online tool to estimate soil N2
O emissions from the cultivation of biofuel crops [20
]. Soil organic matter content, pH, and other environmental conditions were taken into account and the parameters were adjusted accordingly in the GNOC online tool. The NH3
emissions from applied mineral fertilizers are calculated by constant emission factors for each group of fertilizer. The applied emission factor for NPKS 4-16-32-2S was 4% of the used amount, 2% for ammonium nitrate, 8% for ammonium sulfate, 5.7% for KAS N25+S3 according to Nemecek and Schnetzer, 2012. Fossil CO2
was released in the use of urea fertilizer, and nitrous oxide (NOx
) may also be produced during denitrification processes in soils: both emissions were calculated according to Nemecek and Schnetzer, 2012 [21
]. According to the information received from the interviewed agronomist, a straw to seed ratio of 2:1 is assumed considering that rape straw is further ploughed back into soil [8
]. In Latvia, it is a national practice to plough the straw back into the soil [20
]. Returning the rapeseed straw back into the soil enhances the organic content of the soil which is beneficial for the next crop, improves the structure of the soil, and prevents soil erosion [22
The level of agricultural operations for the application of fertilizers and plant protection products varies from year to year (in detail in Fridrihsone et al. 2018 [1
]) so an average was taken. Transport was modeled based on factual information: the distance from the producer/large warehouse (in some cases the specific producer location was not known) to the company’s storage. The average distance from the company’s storage to the field and from fields to the regional processing center, where the grain drying takes place, is 15 km.
Despite having high-quality primary data from the company, it was very challenging to model the agricultural machinery inputs because the ecoinvent database did not contain the specific machinery datasets. It was especially challenging for the soil tillage operations, namely, disc cultivation, drag harrowing, and sowing, together with soil loosening, as there were no such datasets. Agricultural equipment is infinitely more complicated and proprietary today than what is available in the databases. The most relevant datasets in ecoinvent v3.5 were modified so the diesel consumption (and associated emissions) corresponded with the information provided by the agricultural company.
The assessment of indirect land-use change (ILUC) was beyond the scope of this study. It was assumed that direct land-use change did not occur as there have not been any cropland management activities for more than 20 years [23
]. Rapeseed has been cultivated in croplands that have been used for intensive agriculture over the last 50 years [8
Capital goods, overhead, and human labor were not included in the inventory since it was not possible to obtain detailed data on these factors. As noted by Queirós et al., 2015, this approach allows results to be compared with other studies where capital goods are also omitted. Moreover, Malça and Freire et al. reported capital goods are neglected in the majority of studies as they represent only a small fraction of the total impact [24