A phosphorous flow analysis in Spain

1 A Phosphorous Flow Analysis in Spain 1 Jesús Álvarez a, Marc Roca a, Cesar Valderrama a,b*, José Luis Cortina a, b,c 2 a Chemical Engineering Department, UPC-BarcelonaTECH, C/ Eduard Maristany, 10-14 (Campus 3 Diagonal-Besòs), 08930 Barcelona, Spain 4 b Barcelona Research Center for Multiscale Science and Engineering, C/ Eduard Maristany, 10-14 5 (Campus Diagonal-Besòs), 08930 Barcelona, Spain 6 c Water Technology Center CETaqua, Barcelona, Spain 7 8 *Correspondence should be addressed to: César Valderrama 9 Departament of Chemical Engineering, Universitat Politècnica de Catalunya-Barcelona Tech 10 C/ Eduard Maristany, 10-14 (Campus Diagonal-Besòs), 08930 Barcelona, Spain 11 Tel.: 93 4011818 12 Email: [email protected] 13 14 Abstract 15 Phosphorus (P) is a vital macronutrient required to improve the agricultural yields but its excessive 16 use as a fertilizer has resulted in pollution of water bodies leading to eutrophication. With no reserves 17 of phosphorus source in Spain, increased dependence on phosphorus in agriculture have not only 18 increased dependence on imports but also has raised concerns on its future availability as a 19 resource. A Phosphorous Flow Analysis (PFA) was conducted for Spain for the year 2012 focusing 20 on the food production and consumption systems. The results obtained were finally compared with 21 PFA at both country level and continent level (EU-27). To quantify food and non-food flows systems, 22 *Revised manuscript with no changes marked Click here to view linked References 2 country specific data were considered. The sectors covered were crop production (CP), animal 23 production (AP), food processing (FP), non-food production (NF) and consumption (HC). The findings 24 reveal that a total of 325 kt P was imported by Spain in 2012; 66% of which was accumulated in 25 markets stock of food and feed, fertilizers and non-food (91 kt P) while 33% was lost to the 26 environment through land-fill, losses to water bodies, land accumulation and incineration. The largest 27 proportion of losses is associated with water bodies (44.7 kt P) followed by agriculture and land 28 accumulation (42.1 kt P). Wastewater treatment plants (WWTPs) received around 79.5 kt P within 29 wastewater, with 60% being removed in sewage sludge. The 31.7 kt P discharged within final effluent 30 represented the 71% of the total losses to water bodies. Around 69% of the sewage sludge was 31 recycled to agriculture and 27% was sent directly to landfill including the ashes from incineration. Net 32 accumulation was 1.84 kg P/cap which was similar to values reported for the EU-27 average (2.5 kg 33 P/cap). 34 Keywords: Substance flow analysis; MFA; secondary resources; waste management 35 36 1. Introduction 37 The United Nations growth forecast for world population of about 9.7 billion by 2050 (e.g., an 38 increase of 33% over the next 35 years) will undoubtedly represents an increase in demand for 39 fertilizers. This is also based on the forecast made by Food and Agriculture Organization (FAO) for a 40 1.8% annual increase in crop production by 2050 (FAO, 2015). Thus, the key to the shortand long-41 term stability of the food chain is to close the cycles of the main resources, which are necessary to 42 support them (e.g., nutrients as phosphorus (P) and nitrogen (N)). P is an essential element to 43 sustain life since it is part of the crucial biological processes, such as reproduction (e.g., DNA), body 44 3 structures (e.g., bones) and energy supply in the form of ATP (Oelkers and Valsami-Jones, 2008) 45 and it cannot be substituted. It also plays a vital role in enhancing soil fertility, agricultural productivity 46 and therefore, on the global food security. 47 Although there is an increase in the global demand, the low diversity of the phosphate rock deposits 48 and the fact that it is considered a non-renewable resource makes P a critical raw material for a 49 nation dependent on agriculture (Sattari et al., 2012). The availability of the phosphate rock reserves 50 is restricted to five major countries (e.g., China, USA, Russia, Morocco and Sahara) and this global 51 imbalance underlies serious challenges at world scale (Childers et al., 2011, Jasinski, 2014, Cooper 52 et al., 2011). Past estimates suggested a time span of 50-100 years for the complete depletion of 53 these primary P reserves (De Haes et al., 2009; Vaccari and Strigul, 2011; Cordell et al., 2010, 54 Cordell et al., 2009a), but current estimates are relying on 300–400 years depending on the 55 dynamics of demand and supply under current extraction rates (Reijnders, 2014; Scholz and Wellmer 56 2013; Jasinski, 2014). There is also the probability that the price of P increases in the future with 57 increasing demand and depletion as well as the increase of the cost of production and this may affect 58 the affordability and may also escalate the price of food. This scenario could further create 59 geopolitical tensions which could in turn make it difficult for dependent nations to procure P from the 60 main producers. 61 Due to the facts and projections as stated above, the EU has included, in 2014, the P-rock in the 62 critical materials list (EC, 2014a). Thus, nations and regions having no P reserves or having low 63 deposits (e.g., EU with only very few P-deposits in Finland (de Ridder et al., 2012; Reijnders, 2014)) 64 need to initiate a change in the cycle of this critical resource to reduce their dependence on primary 65 sources. The probable solution to the P-challenge has been directed to its sustainable management 66 consisting of its efficient use including higher and better recycling. Such potential solutions can be 67 4 identified by P flow analysis (PFA) studies that provide an insight into how humans have used P, and 68 how P has been transfer to the environment on different spatial scales (Chowdhury et al., 2014). The 69 PFA can also provide knowledge to identify in-sustainable uses for more sustainable P use (Cordell 70 et al., 2012). Various PFA´s have been conducted at a global level (Smil, 2000; Liu et al., 2008; 71 Cordell et al., 2009a) and also at a continent level like the EU (Richards and Dawson, 2008; Ott and 72 Rechberger, 2012) and Africa (Cordell et al., 2009a). PFA’s were also conducted on specific 73 countries like Australia (Cordell et al., 2010), China (Li et al., 2012), Japan (Matsubae et al., 2011; 74 Mishima et al., 2009), Austria (Egle et al., 2014; Seyhan, 2009), Belgium (Coppens et al., 2013), 75 Denmark (Klinglmair et al., 2015), Finland (Antikainen et al., 2005, 2008; Saikku et al., 2007), France 76 (Senthilkumar et al., 2012a,b), Germany (Gethke, 2012), Netherlands (de Buck et al., 2012; Smit et 77 al., 2010), Norway (Hamilton et al., 2015), Sweden (Linderholm et al., 2012a), Switzerland (Binder et 78 al., 2009; Lamprecht et al., 2011), Turkey (Seyhan, 2006; 2009), and United Kingdom (Cooper and 79 Carliell-Marquet, 2013). Such studies have given a qualitative as well as a quantitative description of 80 P flows which in turn have been used to forecast future P requirement and usage, recovery and 81 reuse options so as to secure both food as well as P availability. 82 The results of these analyses have some common findings despite the differences in terms of the 83 territory covered or the purpose of the study. It can be highlighted that some of these countries are 84 net phosphorous importers even those that are net food exporter (e.g., Australia). Substantial losses 85 and inefficiencies have been identified in the P cycles due to the low recycling rates for several P 86 flows with the largest losses within the systems to water and soil accumulations. Some studies 87 highlighted a considerable unexploited potential for improvement. Those efforts should be focused on 88 P removal and recovery at WWTP, as well as the developing more effective methods for recycling 89 bulky wastes such as animal manure, food waste and especially municipal sewage sludge, which 90 5 could potentially substitute a significant part of the total applied mineral P fertilizers. However, 91 resource recycling and, thereby, reducing P fertilizer use appeared to be less promising than 92 scenarios based on reduced food waste or redesigned agricultural systems. 93 Spain, like other European countries, has no P-rock mineral deposits and therefore depends on 94 imported mineral phosphate fertilizers to support Spanish fertilizer industries and agriculture. 95 Therefore, the food security in Spain is at present highly dependent on a secure and affordable 96 supply of mineral fertilizers derived from imported phosphate rock. Based on this context, a PFA 97 analysis of Spain has been conducted focusing mainly on the agriculture, food and fertilizers 98 production and consumption system. Since these are the flows where most of the phosphorus 99 transfer occurs, but including flows from industrial processes and waste management processes 100 which interact with P system. The flow diagram and system boundaries used in the PFA analysis 101 were based on a global perspective, which includes the food system (food consumption–production–102 waste chain), as well as non-food flows (detergent, fertilizer and forestry industries), in addition to 103 obtaining quantitative information on imports, exports, major areas of loss or accumulation. The 104 objective behind the PFA analysis is to identify the areas requiring the primary resources of P and 105 simultaneously to identify available secondary resources. An analysis of the potential contribution of 106 secondary P resources associated with urban wastewaters, identified by the EU as one of the target 107 contribution against the P scarcity, was carried out and results compared to other PFAs as reported 108 worldwide. The study has extracted data on P cycles, industrial and agricultural uses to develop the 109 mass flow analysis using databases available for public consultation. For data not available, 110 published data from mass flow analysis on other country or region was taken into account. This PFA 111 on a global perspective will be especially relevant for the proposed EU approaches: circular economy 112 (EC, 2011, 2014d) and bio-based economy (EC, 2012). 113 6 2. Methodology 114 Material Flow Analysis (MFA), has been used to examine resources such as minerals, water or energy at 115 a wide range of geographical scales (from global to local) (Cordell and Neset 2014). The method was 116 established in the field of Industrial Ecology to aid environmental management for assessing the 117 ‘metabolism’ of human (anthroposphere) or technical (technosphere) systems. The method is based on 118 two scientific approaches: i) mass balance, which enables a systematic assessment and tracking of the 119 flow of materials (e.g., P) between various processes, as well as the imports to and exports from the 120 system (Cooper and Carliell-Marquet, 2013) and finally ii) the system analysis. An important concept 121 regarding mass balance under the MFA is related to the conservation of mass in which a material is 122 transformed during its flow but cannot be destroyed (Baccini and Brunner, 2012). 123 At the global level P flows have been quantified along the whole P use chain (Cordell et al., 2009a). 124 This quantification was then used for: i) predicting the future P use so as to ensure long term global 125 food demand (Cordell et al., 2009b), ii) developing a system so as to recover and reuse P in order to 126 ensure global P security (Cordell et al., 2011, 2013) iii) identifying synergies for a sustainable future 127 based on global P scarcity (Neset et al., 2013) and finally, iv) developing a framework to assess the 128 vulnerability of national and regional food systems towards the multiple-dimensional stressors of P 129 scarcity (Cordell and Neset, 2014). 130 2.1 System description and boundaries 131 The phosphorous flow analysis covers the state of Spain, organized in 19 autonomous regions and 132 including Baleares and Canarias islands. The P flows were focused, primarily, on agriculture and the 133 food production systems since both accounts for more than 50% of all P uses (MAPAMA, 2016a), but 134 also has considered other industrial uses such as phosphorous in fertilizers, detergents, beverages 135 7 and food. Contrary to other EU countries where sewage sludge is incinerated, this scenario in Spain 136 has a marginal contribution. The flows associated with the recovery of P from waste waters and the 137 application of sewage sludge to agriculture has also been considered in the analysis. 138 2.1.1 Data collection 139 The quantification of the P flow network required the use of several data sources, including official 140 statistical databases, surveys and interviews; and published reports. The statistical data mainly 141 contained the amounts of P substances such as P-containing products, sown crop areas, chemical 142 fertilizers being applied to field, crop harvests, milk production, the number of livestock and human 143 population. Data concerning the amount of material flows were collected from European and Spanish 144 MINETAD databases: FAOStat (FAO, 2009), Eurostat (EUROSTAT, 2016), Spanish Ministry of 145 Agriculture, Food, Fishing and Environment (MAPAMA) (MAPAMA, 2016 a, b, c, d), Spanish Ministry 146 of Energy, Tourism and Digital Agenda (MINETAD) (MINETAD, 2016), Spanish Agency for 147 Consumer Affairs, Food Safety and Nutrition (AESON) (AESON, 2016) and National Institute of 148 Statistics (INE) (INE, 2016). When data were not available, the mass balance principle was applied 149 and missing flows were estimated. It is worth to mention that uncertainty was also considered, 150 especially those associated with the variation of P concentrations in goods or the mass flow 151 variability. In the present study, P flows were quantified by multiplying the material flows with their 152 respective P contents (described as an amount of P2O5) and were expressed in kt P /y. 153 The base year of 2012 was chosen as it represented the most recent year for which an almost 154 complete dataset could be gathered, and because it was also the year that an extended review on 155 sewage sludge database was carried out (MAPAMA, 2016 e, f). When data for 2012 was not 156 available, data from 2013 was taken to represent the value. Similar approaches have also been used 157 8 in other PFA in Finland (Antikainen et al., 2005), Japan (Matsubae et al., 2011), Australia (Cordell et 158 al., 2010), United States of America (Suh and Yee 2011), France (Senthilkumar et al., 2014), United 159 Kingdom (Cooper and Carliell-Marquet, 2013) or Denmark (Klinglmair et al., 2015). However, it should 160 be noted that this is a static model and that annual variations may be significant and comparison 161 between years would be very valuable, which would be part of a continuous exercise when more data 162 becomes available. 163 2.1.2. Software platform for modelling 164 The PFA follows the reference guides (Graedel and Allenby, 2010) and the main studies developed 165 for country/region levels described in the introduction. Quantitative modelling of P flow in such 166 complex system is usually done with the help of different mathematical and statistical tools (STELLA, 167 POWERSIM, VENSIM, STAN (Vienna University of Technology, 2012), and MATLAB/Simulink®. In 168 this study, the STAN code was used. STAN tool builds a graphical model with predefined 169 components (processes, flows, system boundary, text fields) where it is entered or import known data 170 (mass flows and stocks, volume flows and stocks, concentrations, transfer coefficients) for different 171 layers (good, substance, energy) and periods to calculate unknown quantities. The code includes the 172 possibility to consider data uncertainties. The algorithm uses mathematical and statistical tools such 173 as data reconciliation, error propagation and gross error detection. 174 2.2. Data management and uncertainty assessment 175 One of the main concerns of MFA is the identification of the potential errors and uncertainty of 176 results. This study has also employed cross-checking of original results through the use of alternative 177 calculations, comparing estimates to values obtained from the literature, and deriving mass balance 178 estimates where possible (Senthilkumar et al., 2012b). In some cases, various estimates have been 179 9 used for the same point, so there have been averages of these flows, which are shown in Table A1 180 (Supplementary Material). The approach was useful to confirm the results by highlighting erroneous 181 results. The double counting was also revised an avoided, for instance imported crops could be counted 182 twice under both crops and under the imported animal feed. To avoid this, commodities with a potential 183 risk of double counting were first identified. The use for each commodity was then determined and 184 categorized into a single flow, ensuring that it was removed from other flows. The information collected 185 shows the dispersion level of the results that have been used to obtain the average values. 186 Confidence range for PFA were obtained by using the HS approach developed by Hedbrant and Sörme, 187 (2001) and widely used in different PFA studies (Seyhan, 2009; Cooper and Carliell-Marquet, 2013, 188 Danius, 2002, Antikainen et al., 2005 and Asmala and Saikku, 2010). The methodology used has been 189 described with more details by Cooper and Carliell-Marquet (2013). Uncertainty levels are assigned to 190 various data sources and then applying an interval to each level. During situations when a series of 191 calculations were used in order to make estimates for the same data points, a confidence interval was 192 developed for each separate calculation as per the methodology described by Antikainen et al. (2005), 193 and finally, an average confidence interval was taken for the overall data points. The details of the 194 defined intervals used and examples are summarized within Table 1. 195 Table 1. Uncertainty intervals used on the PFA in Spain. Level Interval Source of information Example 1 */1,05 Official statistics at Spain scale. Spain population estimate 2 */1,1 Official Statistics at Spain scale. Value from literature. Area of land, crop yields, animal numbers from MAPAMA or INE. P contents from literature 3 */1,2 Official statistics scaled up to Spain scale. Values from literature. Detergent consumption scaled up to Spain scale. Specific values from other studies in literature. 16 products is only around 15%, thus, indicating that 85% of the inputs become manure. 239 The food and feed system receives inputs from agriculture as crops and animal products, as well as 240 imported food and feed materials. The total inputs are 296.28 kt P/y and the output is 223 kt P/y. The 241 difference between both flows suggests an annual stock of 73.28 kt P/y, and this indicates its 242 accumulation within this system. This accumulation may be due to the partial information that justifies the 243 output of P towards other processes; it may also be related to the generation of food stock as cereals, 244 due to market needs or interests. Animal feed was estimated at 77.52 kt P/y and it is the largest output 245 followed by human food consumption with 73.76 kt P/y. It is estimated that the Spanish system 246 generates around 22.96 kt P/y as waste, giving an efficiency of 92 %. 247 3.2 P accumulation and losses 248 P in Spain is accumulated in two different ways; on one hand P accumulated in market stocks of food 249 and feed, fertilizers and non-food, accounting for a total of 90.99 kt P/y, and on the other hand P lost to 250 the environment through incineration, landfill, losses to water bodies and land accumulation, which 251 accounts to a total of 111.56 kt P/y. The largest proportion of losses to environment is due to the losses 252 to water bodies, accounting 44.69 kt P/y, followed by agricultural land accumulation with 42.09 kt P/y as it 253 is shown in Figure 4. The main contributor of P losses to water bodies is the WWTPs treated effluents, 254 estimated in 31.72 kt P/y, which represents around 71 % of total losses to natural water bodies. 255 17 256 Figure 4. P accumulation and losses according to PFA in Spain. The P accumulation in the soils is estimated to be around 42.09 kt P/y, which is equivalent to 12 % of the 257 total input to agricultural land, or equivalent to 26% the amount of P within mineral fertilizer uses. The 258 loss of P through landfill was estimated around 24.78 kt P/y. The largest proportion of this amount is 259 within urban organic waste landfilled, which is estimated to contain up to 16.47 kt P/y. Sewage sludge 260 and waste incineration ash is assumed to be disposed also to landfill with 6.19 and 2.12 kt P/y 261 respectively. 262 263 3.3 P flows affecting environmental compartments. 264 P is an essential resource and should also be considered as a pollutant. As agricultural fertilizers 265 enhance crop growth, increased nutrient loading to aquatic ecosystems promotes eutrophication 266 leading to an abundance of algae and aquatic plants, thereby causing a detrimental impact on the 267 local ecosystem. Freshwaters are generally more responsive to P increases than other nutrients; 268 73.29 11.64 6.06 44.69 16.47 8.31 42.09 Food & Feed Non food Fertilizers Water Bodies Landfill Incineration Accumulating in soils 6% 8% 6% 36% 21% 8% 22% 3% 4% 18 hence P is considered the main driver of eutrophication in lakes, rivers and estuaries of Spain. P 269 enters water bodies through point sources, such as final effluent discharges from WwTw (more than 270 2900 in Spain (MAPAMA, 2016f)) and through non-point or diffuse sources, such as soil erosion from 271 agricultural fields or surface runoff of fertilizers and inappropriate use of animal manures (MAPAMA, 272 2016g). The water treatment industry receives P loads within wastewaters up to 79.47 kt P/y, which is 273 either discharged to natural water bodies or removed after transfer to sewage sludge. It is estimated that 274 around 31.72 kt P/y is discharged (Figure 5) into the treated effluent, indicating a P removal efficiency of 275 around 61 %. 276 277 Figure 5. Phosphorous flows through Spanish wastewater treatment works (WwTw) kt P/y according to 278 PFA. 279 Approximately 69 % of the 47,75kt P/y removed within sewage sludge is recycled in agriculture uses and 280 27 % is directed to landfill and composting and 4 % is sent to other uses. The P flow recycled to 281 agriculture via the treated sewage sludge represents up to 10 % of the total P input to agricultural uses. 282 Incinerated 6.19 P entering wastewater treatment works 79.47 P discharged to water bodies 31.72 P removed within sewage sludge 47.75 Recycled to agriculture 32.89 Landfill 6.62 Compost and other disposal 2.05 19 Accordingly, phosphorus management options in Spain should increase the efficiency and reduce the 283 losses with a special focus centered on the reduction of the P discharges to water bodies (31.72 kt 284 P/y). Such improvements could help to control both the environmental and resource scarcity issues 285 that are associated with the phosphorus challenge (García Albacete et al., 2012; Garrido-Baserba et 286 al., 2015). On a regional level, P balance studies have focused on the river basin levels that are 287 related to the P losses to surface waters and on the identification of eutrophication risk (Buzás, 1999; 288 De Wit and Behrendt, 1999; Delgado and Scalenghe, 2008; Torrent et al., 2007; Ulen et al., 2007). In 289 general, studies have been limited to quantifying the inputs and outputs of a system, but they have 290 not been able to emphasize the nature of flow of the nutrients (N and P) through the system. In 291 contrast, PFA studies focus on P flows throughout entire society and take different sub-sectors and 292 internal flows into consideration. 293 It should be highlighted that Spain is a net P importer providing a weak position in terms of 294 sustainability due to the risk of supply of this raw material and in consequence its agriculture and 295 economic system dependence on external markets. The current P cycle is inefficient compared with 296 other European and non-European countries with large quantities lost in industrial, consumption, 297 waste management routes and P accumulation in soils. It is well known that the increasing long-term 298 phosphorus demand would likely require demand management measures to reduce business-as-299 usual demand by two-thirds, and the remaining third could be met through a high recovery rate of P 300 from human excreta, manure, food waste and mining waste (Cordell et al., 2011). The results indicate 301 that P cycle in Spain has a huge potential for improvement by defining more effective methods of 302 resource recycling and by promoting policies aimed at designing a sustainable P cycle considering 303 other global environmental and social challenges, including: climate change, energy supply, water 304 scarcity, land-use changes, population growth and urbanization trends. 305 20 3.4 Assessment of PFA of Spain with other countries. 306 Cooper and Carliell-Marquet (2013) and Li et al. (2016) have used indicators of new sustainable 307 phosphorus practices that could be useful for monitoring changes over time, defining and comparing 308 performance across countries. The main indicators that have been identified in the literature (fertilizer 309 application, mineral fertilizer application, human consumption, wastewater flow and total input and out-310 put person flows) are summarized in Table 3. 311 Table 3. Definition of P flow indicators (Cooper and Carliell-Marquet, 2013) and (Li et al., 2016). Indicator Definition Units Fertilizer application P fertilizer application on agricultural land kg/ha Mineral fertilizer application Ratio p mineral fertilizer and total P fertilizer applied on agricultural land % Human consumption P utilization from food and non-food commodities kg/cap WWTP effluent Average P discharged in wastewater treatment plant kg/cap Total input Average total input to the country per person kg/cap Total output Average total output from the country per person kg/cap Exported food Average P export through food per person kg/cap Landfill Average P being landfilled in the country kg/cap Manure application Animal manure applied to agriculture land kg/ha Agriculture loss P loss from agriculture land to streams kg/ha Land accumulation P accumulated in agricultural land kg/ha Soil in P input to agricultural land kg/ha Soil out P output from agricultural land kg/ha Agricultural efficiency Ratio P input and output in agriculture % P recovery P recovered from sewage in WWTP % 21 The PFA results have been reported using total quantities of P (in kt P) and were further normalized in 312 terms of population (kg P/cap), land area (kg P/ha) or efficiency estimates (%). Using these ratios it is 313 possible to compare between countries, territories or cities with different population sizes and agricultural 314 areas. A selection of the main published PFA from Japan, USA, Oceania (Australia and New Zealand) 315 and Europe (France, Finland, United Kingdom, Denmark) and a study from the EU27 are summarized in 316 Table 4. 317 Table 4. A comparison of P flows and selected indicators for different countries and regions. Indicator Units Spain a France b UK c Finland d EU27 e Japan f NZ g Australia h USA i Fertilizer application kg/ha 22.89 10.00 4.00 14.90 6.75 87.00 18.00 1.00 4.00 Mineral fertilizer application % 0.52 0.37 0.27 0.61 0.42 0.73 0.57 0.43 0.81 Human consumption kg/cap 1.56 1.80 0.80 1.00 1.54 0.80 2.30 2.10 1.20 WWTP effluent kg/cap 1.68 0.70 0.40 0.10 0.24 0.10 0.90 0.50 2.60 Total input kg/cap 6.88 7.50 2.20 41.20 4.87 5.70 54.70 25.90 25.30 Total output kg/cap 2.33 2.70 0.40 3.10 2.99 0.00 20.30 6.90 17.60 Exported food kg/cap 0.54 2.10 0.30 0.50 0.49 0.00 10.40 5.20 1.30 Landfill kg/cap 0.35 0.80 0.30 0.50 1.56 0.70 8.60 0.60 1.60 Manure application kg/ha 9.72 10.60 9.70 8.60 9.17 31.60 13.20 1.20 1.00 Agriculture loss kg/ha 0.89 1.60 0.80 1.10 0.44 8.60 4.70 0.10 2.00 Land accumulation kg/ha 3.06 5.80 2.20 12.70 4.85 81.10 85.60 1.70 1.60 Soil in kg/ha 25.60 26.70 15.60 24.90 17.45 118.80 31.40 2.20 7.80 Soil out kg/ha 21.65 20.90 13.40 12.20 12.16 37.00 24.00 0.50 6.10 Agricultural efficiency % 0.85 0.70 0.80 0.50 0.70 0.30 0.70 0.10 0.80 P recovery % 0.44 0.28 0.41 0.24 0.38 0.47 0.00 0.33 0.30 22 Year 2012 2002-06 2009 1995-99 2005 2005 2012-14 2001 2007 a: this study, b: (Senthilkumar et al., 2014), c: (Cooper and Carliell-Marquet, 2013), d: (Antikainen et al., 2005), e: (Ott and Rechberger, 2012), f: (Matsubae et al., 2011), g: (Li et al., 2016), h: (Cordell et al., 2010), i: (Suh and Yee 2011). The comparison as shown in Table 4 has the limitation of covering a time frame from 2001 to 2014, 318 which makes it difficult to draw conclusions; however some trend can be identified. PFA studies 319 specifically showed significant differences between countries and also between regions within 320 countries as discussed qualitatively by Schröder et al. (2011) and compared by Jedelhauser and 321 Binder (2015). The European PFA studies differ in data, methodology and outcomes. In any case, 322 national PFA studies provide positive inputs as they use national parameters, specific knowledge and 323 assumptions to quantify the flows, as well as country specific aspects such as agricultural system 324 types, food habits, and waste management policies. 325 A comparison of P recovery efficiency in Spain vis-à-vis other countries (data taken from Table 4) is 326 graphically represented in Figure 6. It is evident that regardless of the country studied, the P recovery 327 efficiency is below 50% with New Zealand showing a zero recovery. This indicator provides an 328 appropriate guide to identify the use of the main secondary source of P. In the case of Spain, this 329 parameter has reported 44% (0.44) above the average of EU27 (0.38) and UK with 0.41 and far away 330 from France with 0.28. This is mainly due to the different legislation within the EU27 member states 331 regarding the agricultural use of sludge from WWTPs. 332 23 333 Figure 6. Comparison of P recovery efficiency of Spain with model countries and regions (source data 334 Table 4). 335 Figure A2 provides the country wise annual sludge potential from municipal WwTw in kg dry matter per 336 hectare of utilized agricultural area and hence, it represents the theoretical recycling potential of sewage 337 sludge in agriculture. The actual utilization is given in percentage of the total annual amount. For most 338 member states corresponding data are available for 2008 or 2009. It can be seen that in Portugal, Spain 339 and UK, highest proportion of sludge have been applied to agriculture which justifies its higher recovery 340 rate than average in EU27. In the case of France and Finland, 50% and 25% of sludge has been applied 341 to agriculture which is also reflected in the lower average ratios obtained. Country wise (EU member 342 states) heterogeneity is observed in Figure A3 regarding the disposal of sludge from the WwTws. 343 Basically, there are only five possible destinations for sludge, but each member state distributes sludge 344 in different proportions as evident from Figure A3. Regarding the destination of the sludge, it is clear that 345 there are three major trends depending on the sludge disposal. 346 The country wise use of fertilizers in terms of the application ratios (kg/ha) and the ratio of applied 347 0.44 0.28 0.41 0.24 0.38 0.47 0.0 0.33 0.30 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Spain France UK Finland EU27 Japan NZ Australia USA P recovery 24 mineral fertilizer to the total applied fertilizer are shown in Figure 7. Fertilizer uses indicate an overdosing 348 trend in Spain up to 4 times the average for EU27 and only approximate the values reported for New 349 Zeeland and far away for the highest values reported for Japan. 350 351 352 24.9 10.0 4.0 14.9 6.8 87.0 18.0 1.0 4.0 0 10 20 30 40 50 60 70 80 90 100 Spain France UK Finland EU27 Japan NZ Australia USA kg P / ha 0.48 0.37 0.27 0.61 0.42 0.73 0.57 0.43 0.81 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Spain France UK Finland EU27 Japan NZ Australia USA Mineral Fertilizer application 25 Figure 7. Comparison of a) fertilizer application (kg/ha) and b) mineral/total fertilizer application of Spain 353 with model countries and regions (source data Table 4). 354 While making a comparison in the case of the ratio of mineral to the total fertilizers, the performance of 355 Spain has approached the average value of the EU27, and is below the highest values reported for 356 countries where the use of sewage sludge in agriculture is reduced option as are the cases of Japan 357 USA or Finland in Europe (Meyer et al., 2015; Nelson and Janke, 2007). 358 The comparative data of the P accumulation on land with respect to different countries (as depicted in 359 Table 4) is shown graphically in Figure 8. In this sense, the performance of Spain is below the EU27 360 average and lower than those reported for France or Finland. The availability of P to the plants is highly 361 dependent on the properties of the soil, especially on the content of calcium, iron and aluminium rich 362 minerals. 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