Water scarcity and environmental impacts related to water use as per production area
The LCA approach includes the potential effects of depriving humans and ecosystems of water resources, as well as the specific potential effects of pollutants affecting water and thus the environment49. Water stress is commonly defined as the ratio of total freshwater consumption to the level of its hydrological availability. ISO 14046 presents a new concept, i.e., WF, which is associated with the LCA approach. The standard's “water scarcity footprint” refers to the potential impacts associated with the quantitative aspect of water use50. Figure 2 shows the WSI per cultivation area of conventional and organic carrot production. In general, there are significant differences in the total value of the WSI in question. For conventional carrot production technology, it is 10.25 m3/ha, while for organic technology, it is only 1.96 m3/ha. In the case of conventional production, treatments using significant amounts of chemicals have the greatest impact on the WSI, i.e., fertilization (mainly mineral) (WSI = 6.85 m3/ha), and chemical plant protection (WSI = 1.19 m3/ha). The analysis of WSI in organic farming showed that its highest value (WSI = 0.84 m3/ha) concerns the harvesting of carrots, while soil preparation ranks second (WSI = 0.45 m3/ha). A slightly lower WSI of 0.38 m3/ha was recorded in the case of transporting the harvested carrots to the farm buildings. It can therefore be concluded that in organic farming, it is (diesel) fuel consumption that has the greatest impact on the water scarcity level.
In order to explain in detail the impact of individual agricultural treatments on the water deficit in carrot production, a detailed WSI analysis was carried out for the treatments that demonstrated the highest values. In the case of conventional technology, it was fertilization (Fig. 3). Upon analyzing Fig. 3, it can be observed that the use of urea, and hence nitrogen, has the greatest impact on WSI with regard to fertilization. Most nitrogen mineral fertilizers have a negative impact on the environment, causing ozone depletion in the stratosphere, groundwater pollution, global warming, and water eutrophication51,52. Processes requiring the use of machinery, i.e., fertilizer spreaders (1%) and the consumption of diesel fuel (0.1%) have the lowest impact on the level of fertilization-induced water scarcity. Such a low impact of diesel fuel results mainly from its relatively low consumption during fertilization, most often using very efficient centrifugal spreaders.
In the case of organic technology, WSI of harvesting was analyzed in detail (Fig. 4). Carrots were excavated with harvesters, which cut the aboveground parts, cleaned the roots and collected them in a hopper. Sometimes the excavation was preceded by mowing the carrot leaves with mowers. Carrot harvesters are machines that require farm tractors with high-power combustion engines, and the harvesting procedure itself is very time-consuming, hence such a large impact of fuel consumption on WSI in carrot harvesting. Despite the above, the share of diesel consumption in the total value of WSI related to carrot harvesting is only 11%. However, when comparing the WSI related to fuel consumed during harvesting and during fertilization, it can be noticed that in the case of harvesting, WSI is approx. 15 times higher.
In LCA, the potential effects of water pollution have traditionally been addressed in impact categories such as (eco) toxicity, acidification, and eutrophication 43,42 . In the WF analysis, the impact of water consumption is generally related to specific goals within a given conservation area, such as: Human Health, Ecosystems Quality and Resources 43 . The impact of water consumption on human health is expressed in DALY and is obtained by modeling the cause-effect chain of water scarcity (lack of irrigation water) leading to malnutrition. Ecosystem quality is assessed by modeling the cause-effect chain of freshwater consumption with the quality of the terrestrial ecosystem, based on the number of species disappearing each year (species * year). On the other hand, the impact of water consumption in the resources category is assessed by modeling the cause-effect chain of freshwater consumption in relation to the depletion of water resources, along with the excess cost (surplus in $) of extracting an additional cubic meter of water 46 . Table 3 shows WF in conventional carrot production related to the three impact categories, and Fig. 5 shows its structure. The total impact of individual processes in the Human Health category is 1.15E-05 DALY, in the Ecosystem Quality category − 1.53E-07 species*year, and in the Resources category − 2.97 $ surplus. For comparison, WF in the above-mentioned impact areas per 1 ha of tomatoes is, respectively: Human Health − 5.00E-03 DALY, Ecosystem Quality − 2.50E-05 species*year53. When analyzing Fig. 5, it can be observed that in all impact categories, fertilization has the greatest environmental impact, the share of which in individual categories is at approx. 67.0-67.7%. Chemical plant protection ranks second, the impact of which in the three categories ranges from 11.9–12.6%. In addition to the treatments related to fertilizers and chemicals, treatments associated with high consumption of diesel fuel, i.e., soil preparation and harvest, have a significant impact on the value of individual categories in carrot production. This confirms the results of many studies, i.e. that the extraction, production and, above all, the use of diesel fuel bring significant damage to the environment 54,55 .
Table 3
Environmental impact related to the use of water in conventional carrot production per area unit (ha)
Specification
|
Total
|
Soil preparat.
|
Fertilisat.
|
Sowing
|
Chemical protection
|
Mechan. care
|
Harvest
|
Transport
|
Human Health (DALY)
|
1,15E-05
|
7,98E-07
|
7,81E-06
|
5,39E-08
|
1,46E-06
|
3,89E-08
|
8,38E-07
|
5,40E-07
|
Ecosystem Quality (species*year)
|
1,53E-07
|
1,18E-08
|
1,03E-07
|
9,51E-10
|
1,82E-08
|
6,00E-10
|
1,15E-08
|
7,47E-09
|
Resources
($ surplus)
|
2,97E + 00
|
2,21E-01
|
2,00E + 00
|
1,67E-02
|
3,59E-01
|
1,09E-02
|
2,19E-01
|
1,41E-01
|
Detailed WF results for the fertilization process in conventional carrot production are presented in Fig. 6. Among the individual factors shaping the environmental impact, what stands out is the consumption of urea, i.e. nitrogen (44.9–47.0% of the total impact in individual categories) and of phosphorus fertilizers, the impact of which is at 31.4% − 32.4%.
In endpoint analysis, the impact of water use is generally related to specific endpoints in a given conservation area: Human Health, Ecosystems Quality or Resources 43 . Table 4 shows WF in organic carrot production as per the three impact categories, and Fig. 7 shows its structure. The total WF values in each category are as follows: in the Human Health category – 2.11E-06 DALY, in the Ecosystem Quality category – 3.00E-08 species*year and in the Resources category – 0.56 $ surplus. The above results are over five times lower compared to the footprint in conventional production (Table 3), and therefore it can be concluded that organic production not only enables the production of healthy carrot, but also has a very positive impact on the broadly understood environment. Upon analyzing the data from Tables 3 and 4, it can be observed that the environmental impact of fertilization treatment in organic production is over thirty times lower compared to the impact of fertilization in conventional production. Moreover, the fact that no pesticides are used means that the impact of chemical plant protection treatments is 0. The largest share in the total value of WF in individual impact categories is that of carrot harvest, from 41.9% (Ecosystem Quality) to 43.1% (Resources). The methodology for calculating WF is very diverse and includes many methods. Moreover, the results of research on WF related to the production of vegetable species presented in the literature often differ in terms of the analyzed system boundaries, production technology, irrigation, etc. Therefore, the possibility of a broad discussion of the results of WF of conventional and organic carrot production is limited.
Table 4
Environmental impact related to the use of water in organic carrot production per area unit (ha)
Specification
|
Total
|
Soil preparat.
|
Fertilisat.
|
Sowing
|
Chemicalprotection
|
Mechan. care
|
Harvest
|
Transport
|
Human Health (DALY)
|
2,11E-06
|
3,96E-07
|
2,39E-07
|
6,39E-08
|
0,00E + 00
|
1,30E-08
|
9,11E-07
|
4,88E-07
|
Ecosystem Quality (species*year)
|
3,00E-08
|
6,49E-09
|
2,92E-09
|
9,61E-10
|
0,00E + 00
|
2,00E-10
|
1,26E-08
|
6,84E-09
|
Resources
($ surplus)
|
5,61E-01
|
1,15E-01
|
5,80E-02
|
1,77E-02
|
0,00E + 00
|
3,64E-03
|
2,38E-01
|
1,29E-01
|
The detailed structure of WF of the carrot harvesting process in organic farming is shown in Fig. 8. The use of machines, i.e. harvesters, has a decisive share (90.3% − 96.6%) in the total value of individual impact categories.
Water scarcity and environmental impacts related to water use as per yield volume
For a more detailed analysis of WF in carrot production, the individual results were also calculated in relation to the production volume expressed in tonnes. Figure 9 shows the value and structure of WSI related to conventional and organic carrot production, per 100 tons of harvest. In conventional technology, the WSI is 19.56 m3/100 t, while in organic technology its value is approx. four times lower and amounts to 4.95 m3/100 t of harvested carrots. In conventional production, the fertilization process causes water shortage at WSI = 13.3 m3/100 t, while in organic farming the value of the index is 0.46 m3/100 t of produce. In the case of organic farming, the highest value of the WSI relates to the harvesting process, at 2.16 m3/100 t. The results presented in Fig. 9 clearly show that organic farming is justified in areas with unfavorable conditions in terms of water resources. For comparison, the WSI in tomato production is 0.016 m3 per 1 kilogram of produce56. Such a high value results mainly from irrigation of the plants.
A detailed analysis of the amount and structure of water shortage for the fertilization process in conventional carrot production (Fig. 10) indicates the prevalent role of nitrogen contained in urea in the shaping of the WSI. The use of urea as a fertilizer causes a water shortage of 5.60 m3/100 t. The consumption of phosphorus fertilizers, for which WSI = 4.08 m3/100 t, ranks second. The mere use of machines, i.e., fertilizer spreaders, causes a slight water shortage, WSI = 0.13 m3/100 t of harvested carrots. For comparison, WSI related only to the use of carrot irrigation water is 0.02 m3/kg of harvested crop57.
In the case of organic farming, the processes related to carrot harvesting have the greatest share in shaping of WSI, and its detailed structure in relation to these processes is presented in Fig. 11. Upon comparing the water shortage caused by fuel consumption in the harvesting process (Fig. 11) and fertilization (Fig. 10), a significant difference can be observed. In the case of harvesting, the WSI related to diesel consumption is 0.24 m3/100 t of harvested carrots, while in the consumption of diesel in the fertilization process, the WSI is 0.01 m3/100 t. Upon comparing the use of the machines themselves in the process of harvesting and fertilization, the results are similar. The use of carrot harvesters causes a water shortage at WSI = 1.86 m3/100 t of produce, and on the other hand, the use of fertilizer spreaders results in a water shortage at WSI = 0.13 m3/100 t of carrots.
The value of WF conventional carrot production technologies, with regard to the three impact categories, is presented in Table 5. The total impact of individual processes per 100 tons of harvested carrots is as follows: Human Health: 2.17E-05 DALY, Ecosystem Quality: 2.88E-07 species*year and Resources: 5.57 $ surplus. Upon comparing the obtained results with the research presented in the literature and conducted with a similar methodology, it can be concluded that for the production of 100 tons of tomatoes, the total environmental footprint for the above-mentioned impact areas, including factors other than water, is respectively: Human Health: 2.7E-01 DALY, Ecosystems Quality: 1.45E-03 Species*year, Resources: 1.05E + 06 $ 58 . On the other hand, the WSI for green beans, per 100 tons of harvest was reported as follows: Human Health: from 2.00E-2 to 1.08E-1 DALY, Ecosystem Quality: from1.10E-3 to 1.80E-3 species*year, Resources: from 1.90E + 2 to 1.40E + 3 $ surplus 59 .
Table 5
Environmental impact related to the use of water in conventional carrot production per yield volume (100 t)
Specification
|
Total
|
Soil preparat.
|
Fertilisat.
|
Sowing
|
Chemicalprotection
|
Mechan. care
|
Harvest
|
Transport
|
Human Health (DALY)
|
2,17E-05
|
1,50E-06
|
1,48E-05
|
1,20E-07
|
2,70E-06
|
6,56E-08
|
1,53E-06
|
9,27E-07
|
Ecosystem Quality (species*year)
|
2,88E-07
|
2,21E-08
|
1,95E-07
|
1,81E-09
|
3,38E-08
|
1,01E-09
|
2,11E-08
|
1,31E-08
|
Resources
($ surplus)
|
5,57E + 00
|
4,15E-01
|
3,80E + 00
|
3,32E-02
|
6,66E-01
|
1,84E-02
|
4,00E-01
|
2,45E-01
|
Similar to conventional production, Table 6 presents WF in organic carrot harvest, per three impact categories. The total WF values in each category are as follows: Human Health: 5.36E-06 DALY, Ecosystem Quality: 7.62E-08 species*year and in Resources: 1.43 $ surplus. Upon comparing Tables 5 and 6, it can be concluded that, in relation to conventional farming, the environmental impact of organic farming in all three categories is from 3.8 to 4.0 times lower. A higher WF associated with the transport and harvesting of organic crops, compared to conventional ones, results from the lower efficiency of harvesting and transporting of organic carrots. In several organic plantations, carrot harvesting was carried out in two stages. First, carrot leaves were mowed and only in the second stage the roots were excavated with harvesters. This not only extended the harvest time, but also increased fuel consumption per the volume of the harvested crop.
Table 6
Environmental impact related to the use of water in organic carrot production per yield volume (100 t)
Specification
|
Total
|
Soil preparat.
|
Fertilisat.
|
Sowing
|
Chemical protection
|
Mechan. care
|
Harvest
|
Transport
|
Human Health (DALY)
|
5,36E-06
|
1,02E-06
|
5,76E-07
|
1,63E-07
|
0
|
3,36E-08
|
2,33E-06
|
1,25E-06
|
Ecosystem Quality (species*year)
|
7,62E-08
|
1,67E-08
|
7,03E-09
|
2,45E-09
|
0
|
5,19E-10
|
3,21E-08
|
1,75E-08
|
Resources
($ surplus)
|
1,426889
|
0,294921
|
0,139667
|
0,045148
|
0
|
0,00943
|
0,608882
|
0,32884
|