Assessing the Impact of Water Use in LCA of Conventional and Organic Carrot Production in Poland


 As global water resources are decreasing and the demand for it is constantly increasing, the problem of proper water management is becoming more pressing. Poland is one of the largest producers of vegetables in Europe, including carrots, with significant exports. However its freshwater resources are relatively small. The paper presents the results of research on the water footprint (WF) life cycle assessment (LCA) in conventional and organic carrot production. The methodology of calculating WF was used in accordance with PN-EN ISO 14046. It was found, e.g., that the water scarcity index (WSI) for organic production of carrot (WSI = 1.9 m3∙ha-1) is over five times lower, as compared to conventional production (WSI = 10.4 m3∙ha-1). In the case of conventional production, the fertilization process (67.0% - 67.7%) has the greatest impact on the shaping of WF in the individual impact categories, i.e. Human Health, Ecosystem Quality and resources. In organic production, the WF-shaping factor is carrot harvesting (41.9% - 43.1%). The research can be used to develop pro-ecological carrot production technologies, as well as to shape sustainable development plans in agricultural areas. It can also be used to outline policy directions regarding foreign trade in water-consuming agricultural products.


Introduction
As one of the most important natural resources, water is essential for maintaining the integrity of ecosystems and for the development of human society and economy 1,2,3,4,5 . One of the signi cant threats to the global economy and to the human population is the constantly diminishing freshwater resources and the progressive water de cit in ever larger areas of the globe 6, 7, 8, 9 . In parallel with resource depletion, human demand for water has increased almost eightfold in the last 100 years 10 .
Until recently, freshwater resources, its availability, use, and management were dealt with mainly at local and national levels 11 . For many years, the focus has been on the impact of climate change on freshwater resources, and the societal impact on the water management issues was ignored 12 . The recognition of the problem of accelerating changes in water availability, as well as the impact of globalization on water management, has prompted many researchers to raise the issue of freshwater resources and their consumption in a global context 11 .
When assessing water resources, the quality of available water is also essential, in addition to its quantity, as studied by many researchers 13,14,15,16,17 . The worldwide increase in environmental awareness among agricultural producers and consumers has sparked interest in WF of agricultural production. WF is a direct and indirect water consumption index introduced into the water management science to demonstrate the importance of consumption patterns and the global dimension of proper water management 11,18 . WF considerations have gained momentum as the ISO 14046 standards were published 19 , which encouraged certi cation activities in the food production system 20 . The importance of water consumption in the context of life cycle assessment (LCA) was mentioned many years ago 21,22,23,24,25,26 . The very concept of WF is an indicator of direct and indirect water use 18 . The WF LCA methodology considers the total amount of water used by a production system, from cradle (raw material extraction) to grave (waste management) 27 .
Water management of individual countries is very often based on a purely national perspective, striving to match domestic water demand with national water resources and generally disregarding the global dimension of water management. Many countries trade in water-intensive goods, but not all governments are interested in saving water by importing waterintensive products or using the relative abundance of water to produce water-intensive goods for export 11 . Understanding and calculating WF of agricultural products is essential for the development of a well-thought-out national agricultural, economic and foreign trade policy. A rational international trade in water-intensive products can help reduce water scarcity or can increase water consumption in water-scarce regions 28,29 . One of the largest consumers of water in the world is agriculture 30,31,32,33 . In fact, water abundance is one of the main factors increasing land productivity,, agricultural productivity and, consequently food security 34 . Moreover, as 70% of the freshwater consumed by humans is used in agriculture, it is therefore essential to better understand the complex relationship between water and agriculture 35 .
Poland is one of the largest agricultural producers in Europe, especially in regard to the production of vegetables, including carrots. Annually, 700-800,00 tons of carrots are produced, of which more than 30,000 tons are exported 36 . Therefore, the problem of the carrot WF in terms of its production and exports seems important, especially since Poland is one of the countries with relatively small freshwater resources, compared to other European countries, and approx. 2.5 times lower amount of water per capita than the European average 37 .

Purpose And Scope
Carrot production technologies vary depending on the production region, soil quality, and potential quality of the harvested crops (conventional and organic production), hence they are characterized by different consumption of production materials and the use of machines in the production process 38 . Therefore, it can be assumed that different production technologies have a different WF. This study aimed to analyze WF of conventional and organic carrot production in southern Poland in terms of LCA. The results were analyzed to indicate which stages of individual carrot production technologies have the greatest water consumption, and thus the environmental impact. The research covered 20 plantations, 10 of which are conventional and the other 10 organic, with WF analysis for the production area and for the harvested crops. Due to the relatively large amounts of water needed to sustain food production for an ever-growing population, its scarcity in agriculture is an increasing problem. Therefore, WF calculation can be used to identify and assess water use in various carrot production technologies. WF analysis can also be used to determine the potential environmental impact of water use in conventional and organic farming technologies. According to Jolliet et al. 39 , WF analysis can be used to support the sustainable development goals, hence the results can be used to monitor progress in introducing sustainable production. In addition, WF is regarded as a serious assessment tool for the effects of the consumption of water-related goods and services 40 , and the obtained study results can serve this purpose by e.g., indicating which particularly water-intensive means of production used in carrot production should be produced in countries with high water availability, and imported thence. Due to Poland's very large carrot exports and relatively low water resources, the WF analysis may support the development of foreign trade policy.

Subject of the research
The farms with carrot plantations included in the research are located in southern Poland, where high-quality soils are abundant. All farms have a long carrot production tradition and are equipped with specialized eld work machinery. The varieties of carrots used (Kalina, Kometa, and Anka) are the most common in Poland, and their yields ranged from 35-49 t/ha (40 t/h on average) for organic production and 43-65 t/ha (54 t/ha on average) in conventional production. The average area of plantations is 0.94 ha for organic and 1.19 ha for conventional plantations. Both conventional and organic crops were not irrigated. The average transport distance is 0.9 km for organic plantations, and 1.2 km for conventional. The research covered 10 organic and 10 conventional plantations.

System boundaries
In the Life Cycle Assessment (LCA) methodology, a system boundary is de ned to establish the test subject and what could possibly have been omitted. One of the most frequently used approaches in LCA research is the so-called "cradle-togate" method, i.e. taking into account all processes, from the extraction of raw materials from the ground (cradle), to transport, re ning, processing and production, until the product is ready to leave the factory gate (in this case farm) to be transported to the consumer. Figure 1 shows the system boundaries for organic and conventional farming. In both cases, the cradle-to-gate approach was used, omitting the processes related to supplying the means of production to the farm and the post-harvest preparation of carrots for sale, and the sale process itself. The processes related to soil production, mineral and organic fertilization, sowing seeds, mechanical and chemical protection of plants, harvesting, and transport from the eld to storage facilities on the farm were analyzed in detail.

Water footprint calculation methodology
When analyzing water consumption in quantitative and environmental aspects, the applied LCA approach was used to assess the total consumption of resources in relation to environmental damage, i.e., water depletion 41 . LCA comprises four phases: goal de nition and scoping, inventory analysis, impact assessment, and interpretation. Quantitative impact indicators are presented in the middle phase of the impact assessment 42 . As mentioned above, in the LCA methodology, studying the impact of water consumption in production processes takes into account the total amount of water used by the production system, from water required to source raw and production materials, to water required to manufacture and operate machinery involved in the production process, to water used directly in the production process, etc. In the LCAbased methodology, most existing methods quantify water scarcity by taking into account the ratio of water use to its availability and express it as the scarcity, or stress index 43 . This study evaluated the effects of midpoint and endpoint water intake; the midpoint water intake study used a detailed WF calculating methodology developed by P ster et al., 44 . Water scarcity index (WSI) is estimated based on the withdrawal water to availability ratio (WTA) and modeled using a logistic function (S-curve) to t the resulting index values between 0.01 and 1 m 3 deprived/m 3 consumed. The curve is adapted using OECD water stress thresholds that moderate and severe water stress as 20% and 40% of withdrawals, respectively. Water withdrawal and availability data were obtained from the WaterGap model. The index is applied to the volume of drinking water used. The environmental impact of endpoint water use was calculated according to the methodology by P ster et al., 45 .
In endpoint analysis, the impact of water use is generally related to speci c endpoints in a given conservation area: Human Health, Ecosystems Quality or Resources 43 . The impact of water use on human health is determined by modeling the causal chain of water scarcity (lack of irrigation water) leading to malnutrition, and is expressed in DALYs. Ecosystem quality is determined by modeling the causal chain of freshwater consumption impact on terrestrial ecosystem quality, and is assessed by species disappearing per year (species*year). The impact of water consumption in the Resources category, on the other hand, is determined by modeling the causal chain of freshwater consumption impact with respect to water depletion, and the unit is excess cost ($ surplus) of extracting an additional cubic meter of water 46 . Detailed computation was made using the SimaPro software, ver. 8.1.0.60, commonly used in LCA analyzes. The functional unit to which the obtained results were related was the carrot production area (1 ha) and the carrot harvest volume (100 tons). The tests, calculations, and analysis of the results were carried out in accordance with the recommendations of ISO 14046 19  Life Cycle Inventory (LCI) is a stage of the LCA methodology and involves creating an inventory of input and output data for all process units included in the assessment 23 : the ow of raw materials, materials, water, energy and emissions to soil, water and air. During the research, individual carrot production technologies were analyzed in detail, with particular emphasis on the type of technological treatments and machines used, as well as their working time. The inventory of used materials (fertilizers, pesticides, water, fuel, etc.) and energy in individual carrot production technologies, as well as data selection, were taken with due diligence, according to ISO 14044 48 . Due to methodological di culties in calculating the environmental impact of carrot seeds (not listed in the SimaPro software), the seed material was omitted. Following the calculation of the area of individual plantations and the volume of carrot harvest were calculated, the nal results were compared against the adopted production area unit (1 ha) and the harvested crop unit (100 tons).
In respective technologies, two types of farm tractors were usually used for eld works. For light work, such as chemical spraying, weeding, or transport, tractors with approx. 26 kW were used, and for heavier work, mainly related to soil production -tractors with approx. 56 kW. The technology of soil production was usually quite similar: plowing was carried out in autumn with tractor plows. In the case of organic production, cattle or pig manure was applied before plowing. In the spring, other production treatments were applied: harrowing, cultivating and preparation of drills for sowing. Mineral fertilization was applied only in conventional crops, with the use of tractor-mounted centrifugal fertilizer spreaders. In the year of production, liming was applied only in one organic and one conventional plantation. Sowing was carried out with the use of tractor-mounted precision seeders. None of the researched plantations were irrigated as the rainfall was su cient. In the case of organic crops, mechanical plant care was applied, i.e. weeding with tractor hoes. In organic plantations, weeding was largely done by hand. Chemical protection of the plants consisted in applying pesticides (mainly herbicides and fungicides) using tractor sprayers. The carrot was harvested in one or two stages. In single-stage harvesting, combine harvesters were used to dig up the carrots, remove the aboveground parts, clean and collect the roots. In the two-stage technology, mowers were used to rst cut the carrot leaves, and then the harvesters dug up and cleaned the carrot roots. The carrot was transported in a similar manner, i.e., on agricultural tractors and trailers, the only difference being the amount of transport works, which in turn resulted in much higher carrot yield in conventional production. After transporting to the farm, the carrots were either sold or brie y stored. Post-harvest activities (sorting, washing, packing and shipping) basically did not differ regardless of the type of crop and were not included in the analysis. Table 1 and table 2 show the consumption of means of production and the amount of transport works in both carrot production technologies in question, i.e., organic and conventional.    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 speci c potential effects of pollutants affecting water and thus the environment 49 . Water stress is commonly de ned 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 use 50 . Figure 2 shows the WSI per cultivation area of conventional and organic carrot production. In order to explain in detail the impact of individual agricultural treatments on the water de cit 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 eutrophication 51,52 . 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 e cient 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, acidi cation, and eutrophication 43,42 . In the WF analysis, the impact of water consumption is generally related to speci c 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 53 . 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 signi cant impact on the value of individual categories in carrot production. This con rms the results of many studies, i.e. that the extraction, production and, above all, the use of diesel fuel bring signi cant damage to the environment 54,55 . 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 speci c 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 ve 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. 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 m 3 /100 t, while in organic technology its value is approx. four times lower and amounts to 4.95 m 3 /100 t of harvested carrots. In conventional production, the fertilization process causes water shortage at WSI = 13. 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 signi cant difference can be observed. In the case of harvesting, the WSI related to diesel consumption is 0.24 m 3 /100 t of harvested carrots, while in the consumption of diesel in the fertilization process, the WSI is 0.01 m 3 /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 m 3 /100 t of produce, and on the other hand, the use of fertilizer spreaders results in a water shortage at WSI = 0.13 m 3 /100 t of carrots.
The value of WF conventional carrot production technologies, with regard to the three impact categories, is presented in

Conclusions
One of the effects of human impact on the environment is water consumption. What is more, agriculture is the largest consumer of water. The aim of the study was a comparative analysis of WF associated with two different carrot production technologies: conventional and organic. The LCA methodology used in the research takes into account the potential effects of depriving humans and ecosystems of water resources, as well as the speci c potential effects of emitted pollutants affecting the aquatic environment. WF was analyzed based on two functional units: the production area (hectare) and harvest volume (tons), which enables a more accurate interpretation of the obtained results and a reliable assessment of the impact of conventional and organic technologies on the environmental aspects of water consumption.
The LCA analysis showed that despite the lack of irrigation, carrot production requires signi cant water use and has a signi cant environmental impact, regardless of the technology used. The results of the research clearly show that the organic production of carrot brings bene ts not only by supplying healthy vegetables to the market. It also bene ts the environment, as evidenced by benign effect on ecosystems in various impact categories and good environmental indicators (WSI, Human Health, Ecosystem Quality, Resources). For example, the WSI of the production area is over ve times lower in the case of organic farming (WSI = 1.9 m3/ha), compared to conventional production (WSI = 10.4 m3/ha).
The value of WF in individual impact categories, i.e. Human Health, Ecosystem Quality and Resources, is the most signi cantly impacted by the fertilization process in conventional production (67.0%-67.7%), and in organic farming, by carrot harvest (41.9%-43.1%). In terms of crop volume, WSI in conventional technology is 19.56 m 3 /100 t, where the fertilization process itself causes water shortage at WSI = 13.3 m 3 /100 t. In organic farming, the WSI is 4.95 m 3 /100 t of harvested carrots, and the greatest value share is that of the harvesting process with WSI = 2.16 m 3 /100 t. The listed agricultural treatments with an unfavorable environmental impact in terms of water consumption can become the foundation for the environmental modernization of the production technologies. The signi cant differences in WF of fertilization processes in conventional and organic production reveal the great potential of organic fertilizers in terms of environmentally friendly vegetable production. Due to the signi cant impact of diesel consumption on WF during certain treatments, it seems advisable to modernize the production technology not only by replacing some treatments or production materials, but also by involving the use of less energy-consuming equipment. The results can be used to shape sustainable development plans in agricultural areas. It can also be used to outline policy directions regarding foreign trade in water-consuming agricultural products. Further research will focus on the development of various carrot production technology variants, adapted to local water resources, ensuring high yields on the one hand, and on the other, limiting the negative environmental effects of water use.

Declarations Acknowledgments
Publication was supported with a grant from the Ministry for Higher Education for statutory activities.
Competing interests I declare that the authors have no competing interests as de ned by Nature Research, or other interests that might be perceived to in uence the results and/or discussion reported in this paper.

Additional information
Correspondence and requests for materials should be addressed to Z.K.