Assessment of Composted Pelletized Poultry Litter as an Alternative to Chemical Fertilizers Based on the Environmental Impact of Their Production

: Reducing the use of chemical fertilizers in agriculture is one of the EU Green Deal’s priori-ties. Since poultry production is increasing worldwide, stabilized poultry litter such as composted pelletized poultry litter (CPPL) is an alternative fertilizer option. On the contrary, compared to chemical fertilizers, the environmental impacts of composted products have not been adequately studied, and no data are currently available for CPPL produced by a closed composting system, such as the Hosoya system. The aim of this research was to assess the role of CPPL as a potential alternative for chemical fertilizer by evaluating the environmental impact of CPPL production via the Hosoya system using common chemical fertilizers. Based on life cycle assessment (LCA), the environmental impact (11 impact categories) was determined for the production of 1 kg of fertilizer, as well as for the production of 1 kg of active substances (nitrogen (N), phosphorus pentoxide (P 2 O 5 ), and potassium chloride (K 2 O)) and the theoretical nutrient (NPK) supply of a 100 ha ﬁeld with CPPL and several chemical fertilizer options. The production of CPPL per kilogram was smaller than that of the chemical fertilizers; however, the environmental impact of chemical fertilizer production per kilogram of active substance (N, P 2 O 5 , or K 2 O) was lower for most impact categories, because the active substance was available at higher concentrations in said chemical fertilizers. In contrast, the NPK supply of a 100 ha ﬁeld by CPPL was found to possess a smaller environmental impact compared to several combinations of chemical fertilizers. In conclusion, CPPL demonstrated its suitability as an alternative to chemical fertilizers.


Introduction
Chemical fertilizers provide nutrients to plants quickly and easily. Since relatively low amounts of chemical fertilizers with an increased active substance content are sufficient for productivity [1][2][3], the introduction of chemical fertilizers has decreased the usage of manure to a low level in intensive farming systems. Chemical fertilizers, on the other hand, can hasten the decomposition of soil organic matter, resulting in the degradation of soil structure. Excess fertilization also has the potential to pollute waterbodies by causing leaching and acidity [4][5][6][7]. Furthermore, several studies have shown that the production and use of chemical fertilizers produce high levels of NO x and N 2 O; moreover, the use of fertilizers also increases soil CO 2 emissions [8][9][10][11][12][13][14][15][16][17][18][19][20]. With the overarching aim of making Europe climate neutral and sustainable by 2050, the EU introduced the European Green Deal. One of its key targets is to reduce the overall use of chemical fertilizers. The positive effects of the use of manure as a fertilizer for soil-plant systems, particularly on the environment, highlight the importance of organic matter-based fertilizer applications. The European Commission presented the "Farm to Fork Strategy" in the spring of 2020. This cycle assessment standard is primarily developed for industry, with less frequent application in agricultural systems and byproducts.

Definition of the Goal and Scope of LCA
The main objective of this analysis was to assess the role of CPPL as a potential alternative to chemical fertilizers by evaluating the environmental impact of CPPL production via the Hosoya system using common chemical fertilizers. Based on a life cycle assessment, the environmental impact (11 impact categories) was determined for: • The production of 1 kg of fertilizers: 1 kg of composted pelletized poultry litter (CPPL) and 1 kg of the following chemical fertilizers: ammonium nitrate (AN), calcium ammonium nitrate (CAN), urea, triple superphosphate (TSP), monoammonium phosphate (MAP), and potassium chloride (KCl); • The production of 1 kg of active substances separately for the N, P2O5, and K2O content of fertilizers to provide comparable inputs to assess fertilizer production per unit of nutrient; • The nutrient (NPK) supply of a 100 ha field with 1.5 Mg/ha of CPPL (based on Szabó et al.'s [54] method), and with chemical fertilizer combinations with an equivalent NPK supply to analyze the environmental impacts of CPPL as a multi-element fertilizer.

Life Cycle Inventory Analysis
In the framework of inventory analysis, the input and output materials and energy flows were quantified for the Hosoya composting system using the data of a regionally important poultry producer company in Hungary. In the Hosoya composting plant, deep litter from broiler and layer poultry stock farms and filtered sewage sludge generated by slaughterhouses and hatcheries were collected and treated. The capacity of the plant is 10 mg/day. Poultry houses were littered with heat-treated and grinded straw pellets. Due to the high absorbance capacity of these straw pellets, the deep litter manure also had a low moisture content. The parameters of the broiler and layer manure and litter are shown in Table 1.

Definition of the Goal and Scope of LCA
The main objective of this analysis was to assess the role of CPPL as a potential alternative to chemical fertilizers by evaluating the environmental impact of CPPL production via the Hosoya system using common chemical fertilizers. Based on a life cycle assessment, the environmental impact (11 impact categories) was determined for:

•
The production of 1 kg of fertilizers: 1 kg of composted pelletized poultry litter (CPPL) and 1 kg of the following chemical fertilizers: ammonium nitrate (AN), calcium ammonium nitrate (CAN), urea, triple superphosphate (TSP), monoammonium phosphate (MAP), and potassium chloride (KCl); • The production of 1 kg of active substances separately for the N, P 2 O 5 , and K 2 O content of fertilizers to provide comparable inputs to assess fertilizer production per unit of nutrient; • The nutrient (NPK) supply of a 100 ha field with 1.5 Mg/ha of CPPL (based on Szabó et al.'s [54] method), and with chemical fertilizer combinations with an equivalent NPK supply to analyze the environmental impacts of CPPL as a multi-element fertilizer.

Life Cycle Inventory Analysis
In the framework of inventory analysis, the input and output materials and energy flows were quantified for the Hosoya composting system using the data of a regionally important poultry producer company in Hungary. In the Hosoya composting plant, deep litter from broiler and layer poultry stock farms and filtered sewage sludge generated by slaughterhouses and hatcheries were collected and treated. The capacity of the plant is 10 mg/day. Poultry houses were littered with heat-treated and grinded straw pellets. Due to the high absorbance capacity of these straw pellets, the deep litter manure also had a low moisture content. The parameters of the broiler and layer manure and litter are shown in Table 1. The progress of Hosoya composting followed several steps: Receipt of raw materials-storage, pre-treatment, and mixing: The raw materials were delivered by closed and covered manure transport vehicles. Dehydrated broiler and layer manure and litter were mixed (53% broiler manure and litter, 27% manure layer and litter, and 20% chicken meal). This mixture was stored until use in a closed manure storage building.
Storage of manure to oval tanks: Stored manure was transported to a loading hopper by front loaders. From the loading hopper, manure was transported to the entry points of the Japanese Hosoya-type manure oval tank system by belt feeders with rubber belts. The yearly capacity per a tank is 5000 mg/year. Moisture content optimization: For optimal composting, the moisture of the raw material must be adjusted to 40-45 w/w% by adding sewage sludge (50 L/intake) and water (100 L/intake).
Composting: Controlled and monitored composting took place in the tanks. Proper ventilation was provided by a perforated pipe system at the bottom of said tanks, where the air was blown by a compressor. Depending on the technological need, it was possible to change the air temperature from 15 to 70 • C. The moisture content of the raw materials decreased to 22-28 w/w% by the end of the procedure. Due to the intensive mixing and aeration, very intensive microbiological processes took place in the raw material during the decomposing process. The temperature varied between 60 and 70 • C for several days. At this temperature, weed seeds, which may have come from the litter, already lost their ability to germinate, and the number of colonies of several pathogenic bacteria decreased. The stirring machine with double rotors resulted in continuous mixing of the manure and litter in the tanks. The system completed a full run along the oval tank in approximately 4 h, and the speed of the run was 0.8 m/min. On a daily basis, a maximum of six full runs were able to be completed. One complete run resulted in the displacement of 1.5 m of manure and litter along the tank or a maximum of 9.0 m after six runs completed in 24 h. Otherwise, the raw materials would have cooled down too quickly and this would have hindered the process. The design of the tanks and the applied operational technology ensured a 14-day time period traveling time for fresh manure and litter to reach the exit point as compost ( Figure 2). Continuous operation ensured that the same amount of manure and litter entered the tank as the amount of compost leaving it. In the technology, 5 cm thick compost remained at the bottom of the tank as a microbial starter. This layer was mixed with the added amount of fresh manure and litter.
The progress of Hosoya composting followed several steps: Receipt of raw materials-storage, pre-treatment, and mixing: The raw materials were delivered by closed and covered manure transport vehicles. Dehydrated broiler and layer manure and litter were mixed (53% broiler manure and litter, 27% manure layer and litter, and 20% chicken meal). This mixture was stored until use in a closed manure storage building.
Storage of manure to oval tanks: Stored manure was transported to a loading hopper by front loaders. From the loading hopper, manure was transported to the entry points of the Japanese Hosoya-type manure oval tank system by belt feeders with rubber belts. The yearly capacity per a tank is 5000 mg/year. Moisture content optimization: For optimal composting, the moisture of the raw material must be adjusted to 40-45 w/w% by adding sewage sludge (50 L/intake) and water (100 L/intake).
Composting: Controlled and monitored composting took place in the tanks. Proper ventilation was provided by a perforated pipe system at the bottom of said tanks, where the air was blown by a compressor. Depending on the technological need, it was possible to change the air temperature from 15 to 70 °C. The moisture content of the raw materials decreased to 22-28 w/w% by the end of the procedure. Due to the intensive mixing and aeration, very intensive microbiological processes took place in the raw material during the decomposing process. The temperature varied between 60 and 70 °C for several days. At this temperature, weed seeds, which may have come from the litter, already lost their ability to germinate, and the number of colonies of several pathogenic bacteria decreased. The stirring machine with double rotors resulted in continuous mixing of the manure and litter in the tanks. The system completed a full run along the oval tank in approximately 4 h, and the speed of the run was 0.8 m/min. On a daily basis, a maximum of six full runs were able to be completed. One complete run resulted in the displacement of 1.5 m of manure and litter along the tank or a maximum of 9.0 m after six runs completed in 24 h. Otherwise, the raw materials would have cooled down too quickly and this would have hindered the process. The design of the tanks and the applied operational technology ensured a 14-day time period traveling time for fresh manure and litter to reach the exit point as compost (Figure 2). Continuous operation ensured that the same amount of manure and litter entered the tank as the amount of compost leaving it. In the technology, 5 cm thick compost remained at the bottom of the tank as a microbial starter. This layer was mixed with the added amount of fresh manure and litter. Drying: Due to drying progress, it was further decreased from 22-28 to 10-11 w/w%. Grinding: The dried, heat-treated, and sterile compost raw material was ground into a powder fraction, which became the raw material of the end products.
Pre-storage-nutrient supplementation: The ground compost was supplemented with meat and bone meal as additional nutrients with an 8.6% N content before granulation. Drying: Due to drying progress, it was further decreased from 22-28 to 10-11 w/w%. Grinding: The dried, heat-treated, and sterile compost raw material was ground into a powder fraction, which became the raw material of the end products.
Pre-storage-nutrient supplementation: The ground compost was supplemented with meat and bone meal as additional nutrients with an 8.6% N content before granulation.
Granulation: Granulation occurred after nutrient supplement. Cooling: The pellets could reach 80-95 • C temperature after granulation, so it was required to cool down to 20-25 • C.
Aroma coating-packaging: The shaped and cooled pellets were coated with microcomponents, fragrances, and biostimulators. Finally, the CPPL was packaged. As a result of the above process, the content of the end product was as follows (Table 2). The input flows for the production of 1 kg of CPPL are listed in Table 3. The inputs represent the energy and material flows required for LCA. A part of the data was provided by poultry manure treatment plant (manure, sludge, water, and fuel). However, data administration was based on our own calculations (electricity and emissions).
The inputs for the chemical fertilizers (AN, CAN, urea, TSP, MAP, and KCl) were provided by the Agribalyse database [55]. All parameters (e.g., raw materials, such as ammonia for AN, CAN, urea, and MAP, dolomite and nitric acid for CAN, phosphate rock for TSP and MAP, phosphoric acid for TSP, and potash salt for KCl; electricity; heat; steam in the chemical industry; tap water; and packaging) were included in the calculations, except for the transport processes to the application site, since transport is a highly changing variable in terms of distance, type of transport, and vehicle.

The Life Cycle Impact Assessment
In practice, LCA software is used to carry out life cycle impact assessments. The openLCA software was chosen for this life cycle assessment. Greendelta, a German software development company, created the software in 2006. The software is available for free download and use, and it allows for quick, accurate, and flexible modeling. The openLCA development team ensures that the software is updated on a regular basis.
There are several methods for assessing the impact of a project. The TRACI method, for example, is used in the United States. In Europe, the EcoIndicator, ReCiPe, ILCD, and CML methods are more widely used [56][57][58][59]. In this research, the CML 2001 impact assessment method was used. This method was created at the University of Leiden in the Netherlands in 1992, and its name is derived from the acronym Centrum voor Milieukunde (CML) [57]. The most significant influence of CML's methodology is in the field of "impact assessment". The aim of the CML method is to quantitatively explore all direct material and energy exchange relationships between the natural environment and the product system. On the one hand, the method is based on the assumption that emissions with the same effect can be summarized across media and, on the other hand, on the impact-oriented classification of material and energy flows for impact assessment. The method is in line with international standardization efforts, as it covers target definition (goal and scope), life Agriculture 2021, 11, 1130 6 of 18 cycle inventory (inventory analysis), impact analysis (impact assessment), and evaluation (interpretation of the results) [57].
Within the openLCA software, the Agribalyse database was used because it provides a large number of LCIs of agricultural products [60][61][62].
The impact of emissions and consumption on the environment is illustrated with the following impact categories based on other authors [63,64]: Abiotic depletion potential for elements (kg Sb-eq) (ADPe): The 'abiotic depletion potential for elements' refers to the extent of the use of non-renewable sources and minerals. It shows the per capita use of antimony (Sb) and equivalent substances per year.

2.
Abiotic depletion potential for fossil fuels (MJ) (ADPf): The 'abiotic depletion potential for fossil fuels' is shown in megajoules, instead of unit antimony equivalents (kg Sb-eq) of the resource. 3.
Acidification potential (kg SO 2 -eq) (AP): The acidification potential refers to compounds that cause acid rain (SO 2 , NO x , NO, and N 2 O), usually denoted by the SO 2 equivalent.

4.
Eutrophication potential (kg PO 4 -eq) (EP): The eutrophication potential refers to the effects of over-fertilization or an excess supply of nutrients on terrestrial and aquatic environments, with a focus on the two most important nutrients, nitrogen (N) and phosphorus (P). Eutrophication is indicated as the PO 4 equivalent.

5.
Global warming potential (kg CO 2 -eq) (GWP): The global warming potential is an index improved by the impact of the comparison of different gases on the atmosphere. A higher value of the GWP means a more negative impact on the environment. The basis of the GWP is usually a period of 100 years as the CO 2 equivalent by its measurement. 6.
Ozone layer depletion potential (kg CFC-11-eq) (ODP): To determine the ozone depleting potential, the CFC-11 equivalent is used to describe the emissions of all ozone-depleting substances. 7.
Photochemical oxidation potential (kg C 2 H 4 -eq) (POP): The photochemical oxidation potential describes the ethylene equivalent emissions from photochemical oxidation due to a high NOx concentration. 8.
Fresh water aquatic ecotoxicity potential (kg 1.4-DB-eq) (FAETP): This indicates the amount of contaminants in freshwater that have an impact on aquatic life pollution. 9.
Human toxicity potential (kg 1.4-DB-eq) (HTP): The maximum concentration of compounds that are hazardous to humans. 10. Marine aquatic ecotoxicity potential (kg 1.4-DB-eq) (MAETP): The marine aquatic ecotoxicity potential shows the effects of different chlorine compounds in the atmosphere on marine life and aquatic environments. 11. Terrestrial ecotoxicity potential (kg 1.4-DB-eq) (TETP): This shows the impact of various chlorine compounds on the environment and on humans.

Methods for the Interpretation of LCA Results
During the interpretation of the LCA results, comparative analyses were carried out to assess the environmental impacts of CPPL. At first, the environmental impact of 1 kg of CPPL was assessed compared to chemical fertilizers.
Then, the environmental impacts were determined separately for the production of 1 kg of active substances (N, P 2 O 5 , and K 2 O) ( Table 4). Table 4. Active substance content of fertilizers (N%), (P 2 O 5 %), and K 2 O%) and the amount of fertilizer needed to apply 1 kg of the active substance.

Fertilizers
Nitrogen content (N%) Finally, the environmental impact of producing the nutrient supply of a 100 ha field was assessed and evaluated. The production of 1.5 Mg/ha of CPPL was compared to the production of the CPPL equivalent macro-element content of N, P, and K fertilizers combined. The application of 1.5 Mg/ha (as an optimum based on Szabó et al. [54]) of CPPL was 82.5 kg/ha of active N content, which is in line with Kátai's [65] recommendation of 80 kg/ha as the minimum N requirement for soils with low and medium nitrogen supplies. First, the active substances of 1.5. Mg/ha of CPPL were calculated, and then the CPPL equivalent quantity of the chemical fertilizers was determined for 100 ha (Table 5). In order to supply the CPPL equivalent N, P, and K dosages on a 100 ha field, six combinations of chemical fertilizers were set, and the overall quantity of the combinations was determined (Table 6). The environmental impact of CPPL and the six combinations of chemical fertilizers for fertilization of 100 ha was calculated using the quantity required for NPK fertilization of 100 ha and the previously calculated environmental impacts of 1 kg of CPPL and chemical fertilizers.
The CPPL and NPK combinations were identified to have low, medium, and high environmental impact. Three categories were defined based on dividing the difference between the maximum and minimum environmental impact category values into three equal intervals.

Environmental Impact by Producing 1 kg of CPPL and Chemical Fertilizers
The environmental impact of CPPL production and different chemical fertilizers was evaluated per kilogram of the end product ( Table 7). Out of the 11 impact categories, 9 cases (ADPe, ADPf, GWP, ODP, POP, FAETP, HTP, MAETP, and TETP) of CPPL production had the smallest environmental impact. In the case of the abiotic depletion potential for elements, the best performing chemical fertilizer was TSP, but it was still five times higher than that of CPPL. For the abiotic depletion potential for fossil fuels, the environmental impact of producing 1 kg of CPPL was 93-99% smaller than the chemical fertilizer production.
Only the acidification and eutrophication potentials were the highest in the production of CPPL. The environmental impact of 1 kg of any chemical fertilizer production was 58-93% smaller in the case of the acidification potential and 24-88% smaller in the case of the eutrophication potential compared to CPPL production.
Among the chemical fertilizers, the GWP was the smallest in the production of KCl fertilizer. The highest emissions were found in the N fertilizers, especially in AN. The production of AN produced a five times higher GWP than CPPL.
The ozone depletion potential was the lowest in CPPL production and in KCl (7% higher than CPPL), while urea had the highest (85% higher than CPPL).
In comparison, the environmental impact of CPPL production was 64-93% smaller in the case of the photochemical oxidation potential. The smallest emission value was calculated for KCl production, while the highest was for TSP amongst the chemical fertilizers.
In addition, of the chemical fertilizers, KCl fertilizer production generated the smallest emissions in the fresh water aquatic ecotoxicity potential (seven times higher than CPPL), the marine aquatic ecotoxicity potential (11 times higher than CPPL), and the terrestrial ecotoxicity potential (three times higher than CPPL). The highest emissions were produced by MAP production. The emission values of CPPL production were 92-95% smaller than the MAP production in the case of these impact categories.
The human toxicity potential was the smallest for TSP, while urea had the highest. The emissions from CPPL production were 81-94% smaller than that of the chemical fertilizers.
In summary, for the production of 1 kg of product, CPPL had the lowest environmental impact in 9 out of the 11 impact categories (ADPe, ADPf, GWP, ODP, POP, FAETP, HTP, MAETP, and TETP), while only 2 impact categories (AP and EP) had a higher environmental impact than the chemical fertilizer production.

Environmental Impact by Producing of 1 kg of Active Substance
The environmental impact was determined for 1 kg of active substance (N, P 2 O 5 , and K 2 O) in addition to 1 kg of end product. Accordingly, the AN, CAN, and urea fertilizers were included for 1 kg of the N active substance, while the TSP and MAP fertilizers were included for 1 kg of the P 2 O 5 active substance and the KCl fertilizer was included for 1 kg of the K 2 O active substance content of CPPL.

Environmental Impact by Producing of 1 kg of the Nitrogen Active Substance
Based on the emissions during production, a comparison of the CPPL product and the most major N fertilizers (AN, CAN, and urea) was carried out (Table 8). First, 1 kg of the N active substance was the functional unit. In 6 out of the 11 impact categories (AP, EP, GWP, ODP, POP, and TETP), the environmental impact was higher for CPPL production than for the N fertilizers. In the instance of CAN, the highest abiotic depletion potential for elements was estimated (17 times higher than CPPL). The values of AN and urea were 6.5 and 11 times higher than those of CPPL.
Chemical fertilizers demonstrated abiotic depletion potential for fossil fuels values ranging from 54.8 (AN) to 58.8 MJ/kg N (urea), while CPPL had a value of less than a 10th of these.
The acidification potential of the AN and CAN fertilizers was approximately equal, and the emissions from urea production were the smallest. The acidification potential of CPPL was 96-98% higher than that of the N fertilizers.
CPPL's eutrophication potential was considerably higher than that of the nitrogen fertilizers. The estimated emission values of AN and CAN were equal, while urea had the smallest EP. The emissions show a 15-26 times difference between CPPL and the N fertilizers.
CPPL had the highest global warming potential (nearly 5 kg CO 2 /kg of the N active substance). CAN and AN were close to 4 kg (on average, 16% less emissions than CPPL). Urea had the lowest global warming potential value, which was nearly half that of CPPL.
In comparison to the nitrogen fertilizers, the ozone depletion, photochemical oxidation, and terrestrial toxicity potential values were all higher for CPPL. During the production of CPPL, the values of the above-mentioned impact categories were, on average, 30% higher than in the case of AN, CAN, and urea production.
During the production of CPPL, the values for the impact categories such as the freshwater aquatic ecotoxicity and marine aquatic ecotoxicity potentials, as well as the human toxicity potential, were the smallest. The emissions from the production of CAN were the highest of the impact categories: the freshwater aquatic ecotoxicity potential was 45% higher, while the human toxicity and marine aquatic ecotoxicity potentials were 62-63% higher than CPPL production. The emissions from the production of urea were the lowest of the three N fertilizers in these three impact categories. The freshwater aquatic ecotoxicity potential was 24% higher, while the human toxicity and marine aquatic ecotoxicity potentials were 49-50% higher than CPPL production.
Although only five impact categories (ADPe, ADPf, FAETP, HTP, and MAETP) had lower environmental impacts for CPPL, it should be taken into account that N fertilizers have a much higher N content and were much more concentrated.

Environmental Impact by Producing of 1 kg of the Phosphate Active Substance
The impact assessment of emissions was carried out during the production of phosphate fertilizers in the same way as it was for the N fertilizers. The functional unit used in the comparison of CPPL, TSP, and MAP was 1 kg of the P 2 O 5 active substance ( Table 9). The environmental impact of CPPL was highest for 6 out of the 11 impact categories (AP, EP, GWP, POP, FAETP, and HTP), while for ADPe and MAETP, CPPL was the second largest emitter. Table 9. Impact assessment of the production of 1 kg of phosphate content. The value of the abiotic depletion potential for elements was the highest in the production of MAP, being 5 times higher than CPPL and 14 times higher than TSP.

Impact
The abiotic depletion potential for fossil fuels was smallest for CPPL, being roughly half that of the value of MAP and one-third that of TSP.
In terms of the acidification potential, the emissions during the production of CPPL were, on average, 98% higher than the acidification potential of TSP and MAP.
The highest emissions based on the eutrophication potential were calculated for the production of CPPL. In comparison to the emissions of TSP and MAP production, P 2 O 5 emissions per kilogram were 20 and 56 times higher, respectively.
In the case of the P fertilizers, the values of GWP were similar. The production of CPPL, on the other hand, emitted 83-84% greater CO 2 than the P fertilizers.
Similarly to GWP, the ozone-depleting potential value for CPPL was the highest. CPPL produced emissions that were more than 80% higher than that of the P fertilizers.
The value of the photochemical oxidation potential was the lowest for MAP production. The emission rates for CPPL and TSP were nearly similar. These results were 73-74% higher than the emissions produced by the MAP production process.
The freshwater aquatic ecotoxicity and human toxicity potential values were the highest in the production of CPPL. In comparison to CPPL, the freshwater aquatic ecotoxicity potential was 55% smaller during TSP production and 27% smaller during the production of MAP. In the case of the human toxicity potential, the TSP emissions were the lowest, whereas the MAP production emissions were only 10% lower than in the case of CPPL.
The greatest emissions in the production of MAP were observed in both the marine aquatic and terrestrial ecotoxicity potentials. In terms of the marine aquatic ecotoxicity potential, the MAP and CPPL emissions were nearly similar. TSP production had a 28% lower emission rate than CPPL production. For the terrestrial ecotoxicity potential, the emission value of CPPL production was the lowest. TSP production was 5% higher than the emissions of CPPL, while MAP production was 19% higher.
It can be concluded that the emissions were clearly lower in just three cases-for ADPf, ODP, and TETP-during the production of CPPL. However, it must be taken into account that the phosphate content of CPPL (approximately 3%) was lower than that of the fertilizers.

Environmental Impact by Producing 1 kg of Potassium Content
A comparison was made based on the emissions of CPPL and KCl fertilizer production. For this, 1 kg of the K 2 O active substance served as a functional unit (Table 10). Only ADPe had a lower environmental impact than CPPL (two and a half times lower), while KCl had a lower emission value for the other 10 impact categories. In terms of the abiotic depletion potential for fossil fuels, the production of KCl fertilizer emitted 36% less than CPPL.
The amount of acidification and eutrophication potentials during the production of CPPL was 99% higher than that of the production of KCl.
In comparison to KCl fertilizer production, the global warming and ozone depleting potential values were 94% and 96% higher during the production of CPPL, respectively.
The emission rates were similar according to the results of the photochemical oxidation and terrestrial ecotoxicity potentials. In both impact categories, CPPL production had an 89% higher environmental impact.
In the case of the human toxicity and marine aquatic ecotoxicity potential impact categories, similar rates were obtained. The emission rate of CPPL production was 56-57% higher per 1 kg of the K 2 O active substance. The freshwater aquatic ecotoxicity potential values for the two products were different: the KCl fertilizer production emitted 73% lower emissions than CPPL production.
However, it should be noted that (as with the N and P 2 O 5 substances) CPPL contained much less K 2 O (2.5% K 2 O) than the more concentrated KCl fertilizer (60% K 2 O).

Environmental Impact of a Medium-Sized Farm's Nutrient Replenishment
The environmental impact of producing the nutrient supply of a 100 ha field was assessed and evaluated. The production of 1.5 Mg/ha of CPPL (150 Mg/100 ha) was compared to the production of the equivalent macro-element contents of the N, P, and K fertilizers combined (Table 11). With the production of 150 Mg of CPPL, the abiotic depletion potential for elements and abiotic depletion potential for fossil fuels indicators were the smallest. Meanwhile, the production of various fertilizer combinations produced 93-95% higher emissions than CPPL on average.
However, compared to the chemical fertilizer treatments, the environmental impact of 150 Mg of CPPL production was higher in terms of the acidification potential (94% on average) and the eutrophication potential (90% on average). The possible reason for this, based on de Vries et al.'s [66] research, is that the main contributor to the high acidification potential of CPPL is ammonia, while the high eutrophication potential is due to nitrate emissions.
In comparison to the NPK1 and NPK3 combinations, CPPL produced a smaller global warming potential by 5.5% on average. CPPL's GWP values were similar to those of the NPK2 and NPK4 combinations. The GWP of those combinations where the N fertilizer was urea (NPK5 and NPK6) was 29-33% lower than CPPL due to low environmental impact of urea production, because urea is the most concentrated nitrogen fertilizer (46% N) and smaller amounts of it cover the desired quantity.
There was no substantial difference between the NPK combinations and CPPL in terms of the ozone depletion potential (the values varied between 0.0042 and 0.0053 kg CFC-11-eq).
In those combinations where TSP was used for the P fertilizer (NPK1, NPK3, and NPK5), the photochemical oxidation potential value was, on average, 47% higher than the during the production of CPPL. Meanwhile, the value of this category was 7.5% higher when MAP was used.
The emissions were similar for the impact categories of the freshwater aquatic ecotoxicity potential, the marine aquatic ecotoxicity potential, the human toxicity potential, and the terrestrial ecotoxicity potential. When comparing the production of NPK to the production of CPPL, the freshwater ecotoxicity potential values were around 57% higher, on average, for the NPK fertilizer combinations. The emission value during the production of the chemical fertilizer combinations was, on average, 69-71% higher than the production of CPPL in terms of the human toxicity and marine aquatic ecotoxicity potentials. The terrestrial ecotoxicity potential was also higher in the production of chemical fertilizers, with an average of 50%.
Overall, Table 11 shows that the production of CPPL has a lower environmental impact than the production of equivalent macro-nutrient chemical fertilizers (7 out of the 11 impact categories were of "low environmental impact"). Out of all the chemical fertilizer combinations, NPK5 had the most favorable environmental impact. The NPK1, NPK2, NPK3, and NPK4 fertilizer combinations had the highest environmental impact, since AN or CAN fertilizers were the N source.
Additional calculations were carried out to determine the transportation-related environmental emissions associated with the CPPL and NPK fertilizer combinations mentioned above. To estimate distances of 10, 20, 50, and 100 km, a vehicle with a carrying capacity of 15 t was used. The results of CPPL and NPK fertilizer production were added to the emission data. As a result, transportation had no significant effect on the production-induced changes in emission rates.

Discussion
Although this study evaluated 11 environmental impact categories, the most extensively used and calculated impact category, the global warming potential, was used in order to understand the relevance of the calculated environmental impacts of CPPL and chemical fertilizers.
Since there is a lack of scientific knowledge in the field of environmental impact assessment that includes Hosoya technology's composted and pelletized poultry litter products, the CPPL product was compared with other organic matter treated with semiclosed and closed composting methods (Table 12).
Fresh laying hen manure and carcasses were composted by Zhu et al. [67]. When compared to CPPL based on Hosoya technology, the investigated composting technology emitted 3-6 times less CO 2 . Although, during the 11-week experiment, these compost piles were only remixed and reconstructed once compared to the continuously mixed Hosoya compost. Fresh air was introduced into each compost bin via an air distribution plate to provide ventilation. The emissions were studied during the sewage sludge composting process in the frame of the scientific research program by ADAME [68]. According to their results, the observed emissions ranged between 0.089 and 0.298 kg CO 2 -eq. In the framework of the ADAME program, the emissions from composting livestock waste were also evaluated. The measured emission rate in this investigation was five times higher than the emission value from the Hosoya composting technology.
Luske [69] examined the composting of chicken and cattle manure. The emissions generated from this composting plant were approximately 50% less (0.147 kg CO 2 -eq/kg of the product) compared to the emissions of Hosoya composting technology. The study also demonstrated that the composition and proportion of the input components have a major impact on emissions. Furthermore, composting technology (mixing, aeration, etc.) plays an important role in GWP production. The continuously mixed Hosoya composting technology investigated in this study was moderate compared to the results of other studies. The environmental effects of chemical fertilizer production have been widely studied. The CO 2 -equivalent gas emissions calculated for 1 kg of active substances were summarized to evaluate the results of the present study with other research works (Table 13).
The emissions from the production of AN varied between 3.5 and 7.2 kg CO 2 eq/kg of N at the European level. The highest emission value was measured in China, where 10 kg of CO 2 -equivalent emissions per 1 kg of N-substance were detected [70].
The emission factor of CAN production was also smaller in Europe. The rate of the N substance was 3.7 kg CO 2 -eq [70], while it was 4.2 kg CO 2 -eq for 1 kg of the N substance in this study. The emission factors in Russia, the USA, and China varied between 7.7 and 10.6 kg CO 2 -eq.
In the case of urea production-related emissions, the European emission factors were as follows: 1.6 [71], 1.9 [69], and 3.5 kg CO 2 -eq/kg of N [72]. The value observed in this study was approximately the average of these three factors (2.4 kg CO 2 -eq/kg of N). Higher emission values were calculated in China [70].
Among the P fertilizers, the global warming potential values generated by the production of TSP range from 0.4 to 1.6 kg CO 2 -eq/kg of P 2 O 5 in Europe and throughout the world (1.42 kg CO 2 -eq/kg of P 2 O 5 in this study) [70][71][72].
The emissions from the production of MAP are already much more variable. According to Brentrup et al. [70], the average emission factor is 1.4 in Europe, 1.7 in Russia and the USA, and 2.89 kg CO 2 -eq/kg of P 2 O 5 in China. The factor calculated in present study is between the former two values (1.6 kg CO 2 -eq/kg of P 2 O 5 ). Albaugh et al. [73] recorded a much higher factor in the USA, which was 6.4 kg CO 2 -eq/kg of P 2 O 5 . Based on Zhang et al.'s work [74], it varies between 7.8 and 8.9 kg CO 2 -eq/kg of P 2 O 5 in China. The global warming potential of the N and P fertilizer production in this study is similar to that of other studies in Europe. In general, it was also found that China has the highest values.
The emission factor (0.66 kg CO 2 -eq/kg of K 2 O) in the present study for the production of the KCl fertilizer was close to the highest calculated value in China (0.55 kg CO 2 equivalent) [74]. Based on other studies, the rate of this emission factor is between 0.14 and 0.36 kg CO 2 -eq/kg of K 2 O [73,75,76].
Since Hungary is in the region of Central Eastern Europe, the global warming potential of CPPL production for utilization of 100 ha was also assessed in Europe, including references for Russia. NPK combinations were calculated based on the relevant GWP references for Europe and Russia (listed in Table 13) using the method applied in this study to calculate NPK fertilizer combinations, which is described in Tables 5 and 6. The GWPs were calculated from the average of the European and Russian global warming potential values (Table 14). The global warming potential for producing 150 Mg of CPPL was 40,880 kg CO 2 -eq. In comparison, the average CO 2 equivalent emissions of NPK1 were 27% higher than those of CPPL. The GWP of NPK2 and NPK3 was 19% higher than that of CPPL, while NPK4 had an 11% higher environmental impact. However, for the combinations of NPK5 and NPK6, where the N fertilizer was urea, the environmental impact was 32-36% smaller.

Conclusions
As a final statement, considering the environmental impact by producing 1 kg of active substances, CPPL has a higher environmental impact compared to individual chemical fertilizers. On the contrary, considering that CPPL provides nutrients as a complex fertilizer, the CPPL equivalent combinations of chemical fertilizers have a higher impact in the case of the abiotic depletion potential for elements and abiotic depletion potential for fossil fuels, the photochemical oxidation potential, the human toxicity potential, the freshwater and marine aquatic ecotoxicity potentials, and the terrestrial ecotoxicity potential.
Considering the results, the nutrient (NPK) supply of a 100 ha field with 1.5 Mg/ha of CPPL, as well as combinations of chemical fertilizers with an equivalent NPK supply, CPPL is a potential alternative for the complex fertilization of arable lands. The only exemption is in those cases when urea was used in the NPK combinations (NPK5 and NPK6), due to its low environmental impact. Thus, CPPL can be used as a substitute for chemical fertilizer combinations where N replenishment is not provided by urea. Nevertheless, CPPL provides organic components; a high micro-element content; a number of other beneficial effects on soil fertility, structure, and organic matter content; and water management properties. Therefore, in further research, not only NPK but the micro-element content of CPPL too shall be included in further investigation to assess CPPL as a potential macroand micro-element complex fertilizer alternative for sets of chemical fertilizers.