sustainability

Article Phosphorus Processing—Potentials for Higher Efficiency

Ludwig Hermann 1,*, Fabian Kraus 2 and Ralf Hermann 1

1 Proman Management GmbH, Weingartenstrasse 92, 2214 Auersthal, Austria; [email protected] 2 Kompetenzzentrum Wasser Berlin gGmbH, Cicerostrasse 24, 10709 Berlin, Germany; [email protected] * Correspondence: [email protected]; Tel.: +43-699-1815-9915



Received: 6 April 2018; Accepted: 2 May 2018; Published: 8 May 2018


Abstract: In the aftermath of the adoption of the Sustainable Development Goals (SDGs) and the Paris Agreement (COP21) by virtually all United Nations, producing more with less is imperative. In this context, phosphorus processing, despite its high efficiency compared to other steps in the value chain, needs to be revisited by science and industry. During processing, phosphorus is lost to phosphogypsum, disposed of in stacks globally piling up to 3–4 billion tons and growing by about 200 million tons per year, or directly discharged to the sea. Eutrophication, acidification, and long-term pollution are the environmental impacts of both practices. Economic and regulatory framework conditions determine whether the industry continues wasting phosphorus, pursues efficiency improvements or stops operations altogether. While reviewing current industrial practice and potentials for increasing processing efficiency with lower impact, the article addresses potentially conflicting goals of low energy and material use as well as Life Cycle Assessment (LCA) as a tool for evaluating the relative impacts of improvement strategies. Finally, options by which corporations could pro-actively and credibly demonstrate phosphorus stewardship as well as options by which policy makers could enforce improvement without impairing business locations are discussed.

Keywords: Sustainable Development Goals; Paris Agreement; phosphorus; phosphogypsum; processing efficiency; eutrophication; acidification; economic and regulatory framework; Life Cycle Assessment (LCA)

1. Introduction The scientific committee of the present publication has invited us to present and publish our reflections about phosphate processing within the societal, economic and environmental framework to which all member states of the United Nations are now committed. In this context, we refer to the 17 Sustainable Development Goals of “Transforming our world: the 2030 Agenda for Sustainable Development adopted by the UN General Assembly (193 nations) on 25 September 2015” and The Paris Agreement (COP21) adopted by 195 nations at the 21st Conference of the Parties of the UNFCCC on 12 December 2015. The latter has entered into force on 4 November 2016, thirty days after the date on which at least 55 Parties to the Convention accounting in total for at least an estimated 55% of the total global greenhouse gas emissions have ratified the agreement. In response to the prevailing economic model held responsible for the inefficient resource use, the European Commission has adopted a Circular Economy Package, also in 2015. The Circular Economy aims at redesigning, reusing and recycling resources, materials and products to keep them in the loop and avoid waste. In contrast to the UN-based initiatives, it directly addresses the economic model and may serve as a tool for transition towards sustainable economic principles.

Sustainability 2018, 10, 1482; doi:10.3390/su10051482 www.mdpi.com/journal/sustainability Sustainability 2018, 10, 1482 2 of 19

Consequently, humanity, for the first time in history, has a binding global framework with clear targets underlying societal and economic policies and activities. This normative framework is supposed to protect our planet from nothing less than the risk of catastrophic consequences induced by the ongoing overuse of natural resources and excessive emission of greenhouse gases. However, it is apparently in conflict with—at least the perceived—short-term economic interest of businesses and governments as demonstrated by the Trump administration in the United States. Nonetheless, some industry stakeholders have started to become receptive to the opportunities and potentials unveiled by the present paper and inclined to align its processing activities accordingly.

2. Societal, Environmental and Economic Framework

2.1. Resource Use and Decoupling Steffen et al. [1] saw the timespan from 1901 to 2000 as the century of great acceleration: the global population grew 3.7-fold, total material extraction 8-fold, use of fossil fuels 12-fold, greenhouse gas (GHG) emissions 13-fold, extraction of ores and minerals 27-fold and the global economy at constant prices 23-fold. Hence, per capita GHG emissions increased by a factor 3.5 and ore and mineral extraction by a factor 7.3, outpacing the concurrent economic growth by 17%. The figures reveal that material extraction outpaces population growth by a factor two, indicating that per capita resource use has doubled, from 4.6 to 9.2 tons. Since the global economy during the 20th century expanded by a factor 23 (at constant prices), the per capita income increased six-fold. Hence, the global economy grew by a much larger pace than resource use and population, showing already a spontaneous decoupling of resource use from population growth and per capita income without targeted policy measures [2]. Resource decoupling means reducing the rate of use of (primary) resources per unit of economic activity, commonly expressed as GDP. What we can call increasing resource use efficiency or “dematerialization” is based on using less material, energy, water and land resources for the same economic output. From 1970, per capita resource extraction was stagnating while per capita income continued to rise until 2000, as nicely shown in Figure1 by a comparison of global material extraction and global metabolic rates over time [2]. However, from the beginning of the 21st century, resource use efficiency has declined, i.e., resource use per capita has been on the rise again. While resource use in Western industrialized countries continued stagnating or declining, resource use in Asia has risen and outpaced global GDP growth. The accelerated pace of extraction and consumption of resources goes hand in hand with the increase in global trade. Figures suggest that free trade and globalization has induced production to shift from countries with high resource efficiency to countries with lower resource efficiency. Population is still growing and estimated to reach 9 billion people in 2050, living in urban agglomerations on a planet with limited resources [3]. In the light of the universal agreements on sustainable development (SDGs) and climate change (COP21), it is evident that we cannot continue with business as usual. Deep and permanent decoupling of resource use from human well-being is a universal requirement to which we are all committed. Engineers need to develop, scientists to assess and investors and operators to implement processes that truly increase resource efficiency and reduce the environmental footprint of our industrial operations. We need to produce more with less! Figure1 shows historic (1990–2005) unsustainable global ratios between material extraction and GDP, as well as between metabolic rates and income. Sustainability 2018, 10, 1482 3 of 19 Sustainability 2018, 10, x FOR PEER REVIEW 3 of 19

Figure 1. Global material extraction vs. global global me metabolictabolic rates rates during during 1900–2005 1900–2005 (source: (source: UNEP-IRP, UNEP-IRP, Decoupling natural resource use and environmentalenvironmental impacts from economiceconomic growthgrowth [[2].2].

2.2. Sustainability Sustainability On 1111 December December 1987, 1987, the UNthe GeneralUN General Assembly Assemb definedly indefined a resolution in a Sustainable resolutionDevelopment Sustainable Developmentas Development as Development that meets the that needs meets of the the needs present of the without present compromising without compromising the ability the of ability future ofgenerations future generations to meet their to meet own thei needs.r own It needs. reflected It reflected the conclusions the conclusions of the report of the “Our report Common “Our Common Future” Future”by the World by the Commission World Commission on Environment on Environmen and Development,t and Development, chaired by Grochaired Harlem by Gro Brundtland. Harlem Brundtland.The report, commonly The report, known commonly as the Brundtland known as Report, the Br wasundtland the first Report, official UNwas publication the first official addressing UN publicationthe interdependency addressing of the population interdependency growth, povertyof population and environmental growth, poverty degradation. and environmental It contains degradation.a comprehensive It contains concept a of comprehensive sustainable development concept of and sustainable proposes developm legal principlesent and for proposes environmental legal principlesprotection for and environmental sustainable development protection and [4]. sustainable development [4]. At the time when the report was prepared, 30-years30-years ago, the world was facing problems that sound very familiar to us: unilateralism, unilateralism, falling falling commodity commodity prices prices and and rising rising inequality. inequality. Virtually Virtually all the societal, economic economic and and environmental environmental issues we are currently dealing with were addressed in the report and one could conclude that nothing has happenedhappened since its firstfirst publication.publication. Nevertheless, we havehave seenseen periodic periodic progress progress in in terms terms of resourceof resource efficiency efficiency (1970–2000) (1970–2000) and weand have we noticedhave noticed a strong a strongincrease increase in public in public awareness awareness that—through that—through several several multilateral multilateral efforts effort ands global—leadand global—lead to the to two the twomilestones milestones recently recently achieved: achieved: The 17 The Sustainable 17 Sustainable Development Development Goals andGoals the and Paris the Agreement Paris Agreement to limit tothe limit global the temperature global temperature increase increase by “well by below “well 2 ◦belowCelsius”. 2° Celsius”. On 25 September 2015, the UN General Assembly Assembly (193 (193 nations) nations) has has adopted adopted “Transforming “Transforming our World: thethe 2030 2030 Agenda Agenda for for Sustainable Sustainable Development”. Development”. The 17The Sustainable 17 Sustainable Development Development Goals (SDGs)Goals (SDGs)came into came force into officially force officially on 1 January on 1 2016.January SDG1 2016. and SDG1 SDG2 and are SDG2 eradicating are eradicating poverty and poverty hunger and as hungerthis was as considered this was considered the most important the most and import indispensableant and indispensable requirement forrequirement sustainable for development. sustainable development.In addition, the In SDGs addition, aim atthe achieving SDGs aim universal at achiev healthing universal services, health quality services, education, quality gender education, equality, genderclean water equality, and clean sanitation, water and clean sanitation, energy, goodclean jobsenergy, and good inclusive jobs and economic inclusive growth, economic sustainable growth, sustainableinfrastructure, infrastructure, reduced inequalities, reduced inequalities, sustainable citiessustainable and communities, cities and communities, responsible consumption, responsible consumption,protecting the protecting planet, life the below planet, water life and below life onwater land and as welllife on as peace,land as justice well as and peace, partnerships justice and for partnershipsthe promotion for of the the promotion goals. The of 17 the Sustainable goals. The Development 17 Sustainable Goals Development are presented Goals in Figureare presented2. in Figure 2. Sustainability 2018, 10, 1482 4 of 19 Sustainability 2018, 10, x FOR PEER REVIEW 4 of 19

Figure 2. Sustainable Development Goals [5]. Figure 2. Sustainable Development Goals [5].

Finally, on 12 December 2015, 195 governments agreed at the 21st Conference of the Parties (COP21)Finally, of The on 12United December Nations 2015, Framework 195 governments Convention agreed for Climat at thee Change 21st Conference (UNFCCC) ofon thelong-term Parties (COP21)greenhouse of The gas United emission Nations goals Framework [5]: (1) Keep Convention the increase for Climatein global Change average (UNFCCC) temperature on long-termto “well greenhousebelow” 2 °C gas above emission pre-industrial goals [5]: levels. (1) Keep (2) theAim increase to limit inthe global increase average to 1.5 temperature°C (this would to significantly “well below” ◦ ◦ 2reduceC above risks pre-industrial and impacts of levels. climate (2) change. Aim to (3) limit Aimthe for increaseglobal emissions to 1.5 Cto (thispeak wouldas soon significantly as possible reduce(recognizing risks and that impacts the transition of climate to a change. low carbon (3) Aim economy for global will take emissions longer to for peak developing as soon ascountries) possible (recognizingand (4). Undertake that the rapid transition reductions to a low thereafter carbon in economy accordance will with take the longer best available for developing science. countries) and (4).On Undertake 5 October rapid2016, reductionsthe threshold thereafter for entry in into accordance force of withthe Paris the bestAgreement available was science. achieved—at leastOn 555 Parties October to 2016,the Convention the threshold accounting for entry intoin total force for of at the least Paris an Agreementestimated 55% was of achieved—at the total global least 55greenhouse Parties to gas the emissions Convention have accounting deposited in their total instru for atments least of an ratification, estimated acceptance, 55% of the approval total global or greenhouseaccession with gas the emissions Depositary. have The deposited Paris Agreement their instruments entered into of ratification, force on 4 November acceptance, 2016. approval The first or accessionsession of with the theConference Depositary. of the The Parties Paris serving Agreement as the entered Meeting into of force the Parties on 4 November to the Paris 2016. Agreement The first session(CMA of1) thetook Conference place in Marrakech, of the Parties Morocco serving during as the 15–18 Meeting November of the 2016. Parties to the Paris Agreement (CMAThe 1) took Paris place Agreement in Marrakech, followed Morocco The United during Nation 15–18s Framework November Convention 2016. on Climate Change (UNFCCC)The Paris adopted Agreement at the followed “Rio Earth The Summit” United Nationsin 1992 that Framework entered into Convention force on on21 March Climate 1994 Change and (UNFCCC)The Kyoto adoptedProtocol, at adopted the “Rio in Earth Kyoto, Summit” Japan, inon 199211 December that entered 1997 into and force entering on 21 into March force 1994 onand 16 TheFebruary Kyoto 2005. Protocol, In contrast adopted to the in previous Kyoto, Japan,agreem onents, 11 The December Paris Agreement 1997 and included entering clearly into forcedefined on 16targets February and 2005a Working. In contrast Program to the [6] previous requesting agreements, each nationThe to Paris prep Agreementare, communicate included clearlyand maintain defined targetssuccessive and aNationally Working ProgramDetermined [6] Contributions requesting each (NDCs) nation that to prepare, it intends communicate to achieve. andParties maintain shall successivepursue domestic Nationally mitigation Determined measures, Contributions with the (NDCs)aim of achieving that it intends the objectives to achieve of. Partiessuch contributions. shall pursue domesticThe NDCs mitigation submitted measures, so far withare not the sufficient aim of achieving for meeting the objectives the temperature of such contributions. target. However, The NDCs the submittedagreement so also far requires are not sufficient a review forand meeting update theof th temperaturee national contributions target. However, every the five agreement years, withalso a requiresfirst evaluation a review in and 2023. update of the national contributions every five years, with a first evaluation in 2023. 2.3. Circular Economy 2.3. CircularConcurrently Economy with the UN-lead agreements, the European Commission adopted a Circular EconomyConcurrently Package withincluding the UN-lead revised legislative agreements, prop theosals European on waste Commissionand—responding adopted to the a national Circular Economyand regional Package initiatives including for nutrie revisednt (phosphorus) legislative proposals recycling—a on waste total and—respondingrecast of the European to the Fertilizer national andRegulation. regional The initiatives package for largely nutrient consists (phosphorus) of an EU recycling—aAction Plan for total the recast Circular of theEconomy European covering Fertilizer the Regulation.economic cycle The from package extraction, largely production consists of anand EU consumption Action Plan to for waste the Circularmanagement, Economy recovery covering and therecycling economic of secondary cycle from (raw) extraction, materials. production Its focus and is on consumption decoupling, to triggering waste management, enhanced economic recovery andgrowth recycling by shifting of secondary the economic (raw) materials.activities from Its focus linear is to on circular decoupling, flows triggering [7]. The Action enhanced Plan economicincludes growtha roadmap by shifting with short-, the economic medium- activities and long-term from linear targets, to circular addressing flows production, [7]. The Action consumption Plan includes and waste management. A graphic outline of a Circular Economy is shown in Figure 3. Sustainability 2018, 10, 1482 5 of 19 a roadmap with short-, medium- and long-term targets, addressing production, consumption and wasteSustainability management. 2018, 10, x A FOR graphic PEER REVIEW outline of a Circular Economy is shown in Figure3. 5 of 19

Figure 3. Outline of a Circular Economy, (source: https://www.ellenmacarthurfoundation.org/ Figure 3. Outline of a Circular Economy, (source: https://www.ellenmacarthurfoundation.org/ circular-economy [6]. circular-economy[6]. Apart from the European Commission, the Ellen MacArthur Foundation and McKinsey in cooperationApart from with the the European Stiftungsfonds Commission, für Umweltökonomie the Ellen MacArthur und Nachhaltigkeit Foundation haveand investigated McKinsey the in cooperationpotentials withof a transition the Stiftungsfonds towards a Circular für Umweltökonomie Economy and have und published Nachhaltigkeit a few studies, have investigated the most theprominent potentials being of a “Growth transition within: towards A circular a Circular economy Economy vision for and a competitive have published Europe”. a few [8] In studies, this thereport, most prominenta Circular beingEconomy, “Growth defined within: as an A ec circularonomy economyproviding vision added for value a competitive without consuming Europe” [ 8]. In thisprimary report, resources a Circular and Economy,based on the defined principles as an of: economy (1) preservation providing of addednatural valuecapital; without (2) optimization consuming primaryof resource resources yields and by basedcirculating on the materials principles and of: products; (1) preservation and (3) avoiding of natural externalities, capital; (2) i.e., optimization negative of resourceimpacts on yields air, soil bycirculating and water materialsas well as andon animal products; and and human (3) avoiding life. The externalities,authors claim i.e.,additional negative impactsbenefits on (largely air, soil savings) and water of up as to well €1.8 as trillion on animal per year and and human additional life. The 7% authorsGDP growth claim by additional 2030 in benefitsthree (largelysystems, savings) mobility, of food up toand€1.8 housing trillion (60% per yearof expenses and additional of EU households 7% GDP growth and 80% by of 2030 resource in three use), if circular principles were applied to the European economy. systems, mobility, food and housing (60% of expenses of EU households and 80% of resource use), The term “within” again refers to decoupling and more precisely to the research of the if circular principles were applied to the European economy. Stockholm Resilience Institute that has been culminated in the globally discussed publication of The term “within” again refers to decoupling and more precisely to the research of the Stockholm Steffen et al. (2015) about the planetary boundaries [9]. According to Will Steffen and his colleagues, Resilience Institute that has been culminated in the globally discussed publication of Steffen et al. safe operation planetary boundaries have already been transgressed for biosphere integrity (genetic (2015)diversity), about thenitrogen planetary and phosphorus boundaries [use.9]. According Abrupt and to catastrophic Will Steffen global and his environmental colleagues, safe change operation are planetaryimminent boundaries if we continue have alreadywith business been transgressedas usual. In their for biosphere recent paper integrity “A roadmap (genetic for diversity), rapid nitrogendecarbonization”, and phosphorus Johan use.Rockström Abrupt et and al. catastrophic[10] emphasized global the environmental urgent need for change a “Carbon are imminent Law” if werequiring continue halving with businessgreenhouse as gas usual. (GHG) In their emissions recent ever papery decade “A roadmap from 2020 for to rapid 2050. decarbonization”,In this scenario, JohanGHG Rockström emissions et would al. [10 peak] emphasized in 2020 and thecome urgent to about need zero for by 2050, a “Carbon giving Law”the planet requiring a 75% chance halving greenhouseto stay below gas the (GHG) 2 °C emissionstemperature every Paris decade Agreemen fromt target. 2020to Halving 2050. Inthe this GHG scenario, emissions GHG needs emissions to be wouldcomplemented peak in 2020 by and doubling come torenewable about zero energy by 2050, every giving 5–7 years, the planet a trajectory a 75% chance that we to have stay belowalready the 2 ◦Cstarted temperature by doubling Paris the Agreement use of renewable target. Halvingenergies theevery GHG 5.5 years. emissions Alongside needs with to be renewable complemented energy by doublingsources, renewable carbon capture energy and every storage 5–7 as years, well aas trajectory sustainable that agricultural we have alreadypractices started should by be doublingdeveloped the useand of renewableimplemented. energies Planetary every 5.5boundaries years. Alongside and areas with where renewable the safe energy operation sources, space carbon has capturebeen andtransgressed storage as are well shown as sustainable in Figure 4. agricultural practices should be developed and implemented. Sustainability 2018, 10, 1482 6 of 19

Planetary boundaries and areas where the safe operation space has been transgressed are shown in Figure4. Sustainability 2018, 10, x FOR PEER REVIEW 6 of 19

Figure 4. Planetary boundaries [7]. Figure 4. Planetary boundaries [7]. 3. Phosphorus Processing Following Sustainable and Circular Principles 3. PhosphorusThus Processing far, this paper Following has reviewed Sustainable the norm andative Circular framework Principles governing the activities of responsible policy makers and businesses, including phosphate processing companies. However, the Thus far, this paper has reviewed the normative framework governing the activities of responsible normative framework outlined above is not legally binding, making it difficult and potentially risky policy makersto base investment- and businesses, and/or including operations-related phosphate decisions processing on this companies.framework. This However, is probably the normativethe frameworksingle outlined most important above reason is not the legally circular binding,economy principles making have it difficult not had anda larger potentially impact until risky now. to base investment-Investors and/or do not operations-related put equity into more decisions sustainable on an thisd/or circular framework. practices This without is probably a tangible the return. single most important reason the circular economy principles have not had a larger impact until now. Investors do not put3.1. equity Why intoPhosphorus—Historic more sustainable Development and/or and circular Scarcity practices Considerations without a tangible return. The availability of resources in general and phosphorus in particular has been controversially 3.1. Whydiscussed Phosphorus—Historic repeatedly since Developmentscarcity of resources and Scarcity was first Considerations addressed 1798 by Thomas Robert Malthus writing about the limits to growth of mankind by scarce resources [8]. The term Super Phosphate was Theintroduced availability 1797 ofby the resources British physician in general George and Pearson phosphorus describing in particularCalcium Di-Hydrogenphosphate has been controversially discussed repeatedly since scarcity of resources was first addressed 1798 by Thomas Robert Malthus writing about the limits to growth of mankind by scarce resources [8]. The term Super Phosphate was Sustainability 2018, 10, 1482 7 of 19 introduced 1797 by the British physician George Pearson describing Calcium Di-Hydrogenphosphate (Ca(H2PO4)2) found in bones. Dilute sulfuric acid was first used in Bohemia in 1831 to convert biogenic phosphate in the form of bones and fossilized animal feces (coprolites) to a largely water-soluble form. In 1840, Justus von Liebig made a historic address before the British Association of Science explaining the role of minerals in plant growth and laying the groundwork for modern agricultural science. He was the first to demonstrate scientifically that insoluble phosphates such as bone could be made to release their phosphorus in a form more quickly available to growing plants if they were caused to react with sulfuric acid [9]. Following a similar concept, John Bennett Lawes treated coprolites with sulfuric acid and tested the resultant phosphate as a plant nutrient. In 1842, Lawes was granted a patent on this idea and he established the first commercial Super Phosphate Works. Within the next 20 years, 150,000 tons of Super Phosphate were produced every year in the United Kingdom [9]. The rapid growth of world demand in the 1850s severely depleted the known resources of phosphates—bones, coprolites and guano—prompting Liebig to express his concern that the excessive import of bones by England would not allow other countries a sufficient supply of fertilizers for maintaining soil-fertility. From 1855, Peruvian Guano sustained much of the global phosphate needs before resources were exhausted by the end of the 1870s [8]. During that period, Liebig’s perception of a forthcoming scarcity induced humanity to search for alternative resources and eventually large phosphorite deposits were found in South Carolina, USA. Mining began in 1867 and, having secured raw material supply, the phosphate industry developed in the USA and Europe. By 1889, the mine in South Carolina supplied more than 90% of the global phosphate demand and prospection in Florida was underway [9]. In the 20th century, prospection, mining and processing in other countries followed suit, Office Chérifien des Phosphates (predecessor of OCP Group) was founded in Morocco in 1920. During the 20th century, concerns about phosphorus scarcity reappeared in 1938/1939, 1972 and 1979, mainly in the United States [8]. In 2009, Dana Cordell published the “Peak Phosphorus” thesis in the article “The story of phosphorus: Global food security and food for thought” [10] supporting a wave of P-recycling activities taking off in the beginning of the 21st century in many industrialized countries. Meanwhile, Scholz and Wellmer [11,12] put the phosphorus story into perspective emphasizing the special position of phosphorus among the natural resources despite its comparatively high availability. Phosphorus, like the two other primary nutrients nitrogen and potassium, is a bio-essential element, indispensable and irreplaceable for plant nutrition and all life on earth. SDG 2—Eradication of Hunger—is not attainable without phosphorus, nitrogen, and potassium. Secondary and trace nutrients are doubtlessly beneficial for plant growth, but they are not indispensable for human life [12]. Provided humanity learns how to harvest effectively the energy available from renewable resources [13], long-term supply of reactive nitrogen from the atmosphere and of potassium from seawater should be assured. Other mineral and metal resources are replaceable by similar elements performing the same functionality. Phosphorus does not share its metabolic functionalities with any other element on the planet and thus cannot be replaced. Consequently, mining, processing and use of phosphorus should be subject to extended ethical and information requirements [12]. The good news is that using phosphorus as a fertilizer is only dispersing the element and—if managed properly—large fractions can be recovered, fertilize many sequences of crops and feed many generations of people. Good management means applying circular principles to phosphorus mining, processing, use, recovery and recycling as well as minimizing the environmental impacts of related activities and phosphate use in agriculture. The European Commission has acknowledged the significance of phosphorus, nitrogen and potassium by presenting a revised fertilizer regulation aiming at providing a level playing field for fossil and secondary nutrients as a first deliverable of the Circular Economy Package. Circular principles are a powerful tool to decouple economic growth from material use and essential nutrients are a great choice to start with. Waiting for actual scarcity is certainly not a smart option. Sustainability 2018, 10, 1482 8 of 19

3.2. Economic Framework of Phosphorus Processing After the establishment of the industry in the early 20th century, demand for phosphate fertilizers gradually increased, particularly after World War I. After World War II, fertilizer consumption soared Sustainability 2018, 10, x FOR PEER REVIEW 8 of 19 from slightly above 10 million tons per year in 1961 to 37 million tons in 1987 in-line with the consumption soared from slightly above 10 million tons per year in 1961 to 37 million tons in 1987 overallSustainability resource 2018 use, 10 development, x FOR PEER REVIEW shown in Figure1. Figure5 shows how demand shifted 8 fromof 19 early industrializedin-line with to developing the overall resource countries, use gradually development from shown the earlyin Figure 1970s 1. Figure and more 5 shows pronounced how demand after 1989 with a markedconsumptionshifted from decline earlysoared ofindustrialized from consumption slightly to above developing in developed10 million countries, tons countries per gradually year andin 1961from a continuous tothe 37 early million 1970s risetons and in more1987 developing in-linepronounced with the after overall 1989 resource with a usemarked development decline shownof consumption in Figure 1.in Figure developed 5 shows countries how demand and a countries [14] to around 50 million tons P2O5 consumed today. shiftedcontinuous from rise early in industrializeddeveloping countries to developing [14] to around countries, 50 milliongradually tons from P2O 5the consumed early 1970s today. and more pronounced after 1989 with a marked decline of consumption in developed countries and a continuous rise in developing countries [14] to around 50 million tons P2O5 consumed today.

Figure 5.FigureHistoric 5. Historic phosphate phosphate fertilizer fertilizer consumption consumption in in developed developed (grey) (grey) and anddeveloping developing countries countries (blue) [14]. (blue) [14]. Figure 5. Historic phosphate fertilizer consumption in developed (grey) and developing countries In contrast to common sense economic expectations, market prices did not follow the strong (blue) [14]. Ingrowth contrast path. to commonThey remained sense stable economic and even expectations, declined in real market terms, as prices shown didin Figure not follow6. The light the strong growthgrey path.In dotted contrast They and remained to solid common lines stable senseat the and economic bottom even of declinedexpectations, the graph in show realmarket terms,a marginallyprices as did shown notincreasing follow in Figure thephosphate strong6. The light nominal and declining real rock prices between 1960 and 2008, when a price spike interrupted the grey dottedgrowth and path. solid They lines remained at the bottomstable and of even the graphdeclined show in real a marginallyterms, as shown increasing in Figure phosphate 6. The light nominal long-term pattern. Figure 6 shows that fertilizer prices essentially follow food prices, also declining and declininggrey dotted real and rock solid prices lines between at the bottom 1960 andof the 2008, graph when show a a price marginally spike increasing interrupted phosphate the long-term nominalin real terms and betweendeclining 1960 real androck 2012, prices albeit between with higher1960 and volatility 2008, when compared a price to spikefertilizer interrupted prices. the pattern.long-term Figure6 pattern.shows thatFigure fertilizer 6 shows pricesthat fertilizer essentially prices followessentially food follow prices, food also prices, declining also declining in real terms betweenin 1960real terms and between 2012, albeit 1960 withand 2012, higher albeit volatility with higher compared volatility tocompared fertilizer to fertilizer prices. prices.

Figure 6. Historic fertilizer prices, 1960–2012 [14].

FigureFigure 6. 6.Historic Historicfertilizer fertilizer prices, prices, 1960–2012 1960–2012 [14]. [ 14]. Sustainability 2018, 10, 1482 9 of 19

In the context of phosphorus processing, we are more interested in the long-term trends than in short-term phenomena such as the price peaks in 1974/1975 and 2007/2008, which are due to a coincidence of different influencing factors but certainly not a sign of impending scarcity [14]. The long-term negative price development lead though to exploiting the existing equipment and very low R&D expenses by the industry. As the CEO of the OCP Group nicely explained in a speech given to Massachusetts Institute of Technology (MIT) Sloan alumni in February 2014 [15], OCP Group in 2006 had a negative equity of 1.5 billion USD after having gone through a long period of making losses year after year. Other companies may have performed better but in a market with declining real prices obviously not much room is left for innovation. The 2007/2008 peak and the following years during which prices only gradually returned to “normal” levels spurred investments and we have seen new state-of-the-art facilities being built and operated in several countries, particularly in Morocco, Saudi Arabia, Russia and China. Apart from investing in new capacity, industry started engaging in efficiency improvements and research in new fertilizer types (e.g., controlled release fertilizers) adapted to the requirements of precision agriculture. The increased capacity lead to prices declining again but not coming down to pre-peak levels. In February 2018, phosphate rock prices f.a.s. (free alongside ship) Casablanca (Morocco) stood at USD 86.00/ton, twice the level of February 2006 at USD 42.00/ton and slightly recovered from its post-peak low of USD 80.00/ton in December 2017 [16]. Consequently, phosphate fertilizer producers had been operating in a very difficult economic environment hampering research, innovation and investment into new technologies. However, the industry has used the last decade for vertical integration—most phosphate producers have access to own mines and control the whole value chain—and efficiency improvements with lower environmental impacts. In addition, several companies have started to test using secondary raw materials from recycling activities, for instance admixing ash to phosphate rock upstream of leaching and struvite to complex fertilizer blends (ICL) or producing ammonium nitrate from ammonia stripping at wastewater treatment plants (Yara).

3.3. Phosphorus Processing to Fertilizers In 2016, about 90% of the globally extracted phosphorus was processed to fertilizers and feed phosphates (estimated to represent 7% of P2O5 use) [9] by acidic digestion of phosphate rock concentrate [17]. Worldwide, in terms of P2O5, close to 61 million tons of phosphate rock (concentrate) were extracted and beneficiated, of which close to 45 million tons (74%) were processed to phosphoric acid and about 10 million tons (16%) to Single Super Phosphate [17]. Phosphoric acid is the starting material for most phosphate containing fertilizers in the market with close to 20 million tons Di Ammonium Phosphate (DAP), 13 million tons Mono Ammonium Phosphate (MAP) and 4 million tons of Triple Super Phosphate (TSP). The global capacity of NPK fertilizer production with variable phosphate concentrations close to 110 million tons in 2014. NPKs are partly produced using phosphoric acid as a starting material and partly by digesting phosphate rock (concentrate) with nitric acid. Di Ammonium phosphate (DAP) is the most consumed P fertilizer worldwide with a market share of more than 50% [17]. The various fertilizer processing routes and products are shown in Figure7. Sustainability 2018, 10, 1482 10 of 19 Sustainability 2018, 10, x FOR PEER REVIEW 10 of 19

FigureFigure 7. 7.Fertilizer Fertilizerprocessing processing routesroutes and corresponding products products [18]. [18 ].

3.3. Relevant Waste Flows and Environmental Impacts 3.4. Relevant Waste Flows and Environmental Impacts Roughly three quarters of phosphate fertilizers are produced using phosphoric acid as an Roughly three quarters of phosphate fertilizers are produced using phosphoric acid as an intermediate intermediate product [17], leaving 4–5 tons phosphogypsum (PG) per ton of P2O5 in the acid as productrelevant [17 by-product/waste], leaving 4–5 tons[19]. Currently, phosphogypsum about 85% (PG) of 5.6–7.0 per ton billion of to P2nsO 5PGin produced the acid worldwide as relevant by-product/wastein the lifetime of phosphate [19]. Currently, industry about is disposed 85% ofof in 5.6–7.0 stacks billion in 52 countries. tons PG Three produced to four worldwide billion tons in theare lifetime accessible of phosphate for recovery. industry The stacks is disposed are growing of in stacks by some in 52 200 countries. million tons Three per to year four at billion the current tons are accessiblerate of phosphoric for recovery. acid The production stacks are [19]. growing by some 200 million tons per year at the current rate of phosphoricPhosphogypsum acid production is composed [19]. mostly of calcium sulfate and is a by-product of the reaction betweenPhosphogypsum sulfuric acid isand composed phosphate mostly rock in of the calcium manufacture sulfate of andphosphoric is a by-product acid. It is produced of the reaction in a betweenhydrated sulfuric form, acid the anddegree phosphate of hydration rock in dependi the manufactureng on the of process phosphoric conditions, acid. It issuch produced as the in a hydratedtemperature, form, the the P2 degreeO5-concentration of hydration and depending the free sulfate on the cont processent. The conditions, main forms such of phosphogypsum as the temperature, theproduced P2O5-concentration are the dihydrate and the form free (CaSO sulfate4·2H content.2O) and The the main hemihydrate forms of form phosphogypsum (CaSO4·½H2O). produced After separating the phosphoric acid from the insoluble rock constituents, typically1 by a tilting pan filter, are the dihydrate form (CaSO4·2H2O) and the hemihydrate form (CaSO4· 2 H2O). After separating thethe phosphoric wet phosphogypsum acid from is the sent insoluble to a residue rock pile constituents, (stack) for storage, typically usually by a after tilting washing pan filter, to remove the wet phosphogypsumtraces of phosphoric is sent acid to aand residue fluoride. pile Since (stack) hemihydrate for storage, and usually other hydrate after washing forms convert to remove rapidly traces ofto phosphoric the dihydrate acid form, and fluoride.dihydrate Sinceis the hemihydratedefault form. andPhosphogypsum other hydrate may forms contain convert low rapidlyresidual to concentrations of radium from the source rock (and other metals) and hence can potentially have a the dihydrate form, dihydrate is the default form. Phosphogypsum may contain low residual level of radioactivity associated with radon gas, which is the main reason regulators have limited or concentrations of radium from the source rock (and other metals) and hence can potentially have even forbidden its use, for instance the US EPA in Florida [9]. a level of radioactivity associated with radon gas, which is the main reason regulators have limited or Numerous solutions for phosphogypsum use have been investigated during several decades by even forbidden its use, for instance the US EPA in Florida [9]. many regional, national and global institutions such as the Aleff Group (UK) [20], the International FertilizerNumerous Association solutions [17], for the phosphogypsum Florida Industrial use and have Phosphate been investigated Research Institute during several (FIPR) decades[19], and by manythe International regional, national Atomic and Energy global Association institutions (IAEA) such as[9]. the The Aleff body Group of research (UK) [work20], the has International produced Fertilizermany publications Association proposing [17], the Florida different Industrial use options and including Phosphate agriculture, Research Instituteconstruction (FIPR) and [ 19ceramics.], and the InternationalThe IAEA Safety Atomic Report Energy published Association 2013 (IAEA)[9] was [considered9]. The body a potential of research game-changer work has by produced some manystakeholders publications and, proposingin some countries, different good use examples options including exist of beneficial agriculture, use of construction PG, for instance and for ceramics. soil The IAEA Safety Report published 2013 [9] was considered a potential game-changer by some Sustainability 2018, 10, 1482 11 of 19 stakeholders and, in some countries, good examples exist of beneficial use of PG, for instance for soil improvementSustainability 2018, in10, Brazil,x FOR PEER but REVIEW the real breakthrough may depend on a changing global 11 economic of 19 framework and technological progress in terms of efficient recovery technologies [21]. Disposing PG in improvement in Brazil, but the real breakthrough may depend on a changing global economic the sea as still practiced by OCP in Morocco is not a sustainable solution. However, as Mustafa Terrab, framework and technological progress in terms of efficient recovery technologies [21]. Disposing PG the CEOin the of sea the as OCP still Group,practiced stated by OCP in a in presentation Morocco is not at thea sustainable Massachusetts solution. Institute However, of Technology as Mustafa [15], OCPTerrab, plans to the phase CEO out of thisthe OCP practice. Group, stated in a presentation at the Massachusetts Institute of FromTechnology a regional [15], OCP environmental plans to phase point out this of practice. view, PG may be the single most critical processing issue of fertilizerFrom a regional production. environmental Large volumespoint of view, of acid PG ma processy be the water single insidemost critical and onprocessing top of theissue stacks are frequentlyof fertilizer leaching production. to theLarge ground volumes water of acid and process to adjacent waterrivers inside andand lakeson top [ 22of, 23the], stacks even decadesare afterfrequently the stack beingleaching closed to the and ground covered water by and vegetation. to adjacent Every rivers now and lakes andthen [22,23], the even dam decades at the topafter or the bottomthe cracks stack being leading closed to spills and ofcovered hundreds by vegetation. of thousands Every of now cubic and meters then ofthe acid dam process at the top water or the into the environmentbottom cracks [24] or leading into the to spills groundwater of hundreds through of thou so-calledsands of cubic sinkholes meters [25 of], acid as frequently process water occurring into in the environment [24] or into the groundwater through so-called sinkholes [25], as frequently Florida. An aerial image of a typical phosphogypsum stack is shown in Figure8. occurring in Florida. An aerial image of a typical phosphogypsum stack is shown in Figure 8.

Figure 8. Phosphogypsum stack in Huelva, Spain—closed since 2010 (Source: Mesa de la Ria). Figure 8. Phosphogypsum stack in Huelva, Spain—closed since 2010 (Source: Mesa de la Ria). The nature of the phosphogypsum management issues is probably best demonstrated by a 2015 Thesettlement nature between of the the phosphogypsum US Environmental management Protection Agency issues and is probablythe world bestleading demonstrated phosphate by a 2015fertilizer settlement producer between Mosaic the Fertilizer US Environmental LLC binding Protection Mosaic to commit Agency close and to the 2 billion world USD leading in funding phosphate fertilizerand penalties producer to Mosaic ensure Fertilizerthe proper LLCtreatment, binding storag Mosaice and todisposal commit of an close esti tomated 2 billion 30 million USD tons in funding of hazardous waste (mainly phosphogypsum) at six facilities in Florida and two in Louisiana. Under and penalties to ensure the proper treatment, storage and disposal of an estimated 30 million tons of the settlement, Mosaic Fertilizer will establish a USD 630 million trust fund, which will be invested hazardousuntil it waste reaches (mainly full funding phosphogypsum) of USD 1.8 billion. at six facilitiesThese funds in Florida will cover and the two future in Louisiana. closure of Under and the settlement,treatment Mosaic of hazardous Fertilizer wastewater will establish at four a Mosaic USD 630 facilities—the million trust Bartow, fund, New which Wales will and be Riverview invested until it reachesplants full in fundingFlorida and of USDthe Uncle 1.8 billion. Sam plant These in fundsLouisiana—as will cover well the as futurethe long-term closure care of and of treatmentthose of hazardousfacilities and wastewater three additional at four facilities Mosaic that facilities—the are already undergoing Bartow, New closure Wales [25]. and Riverview plants in Florida and the Uncle Sam plant in Louisiana—as well as the long-term care of those facilities and three3.4. additional Life Cycle facilities Assessment that as a are Powe alreadyrful Tool undergoing for Decision Making closure [25]. Life cycle assessments should be performed in full compliance with the corresponding standard 3.5. LifeISO Cycle 14040:2006. Assessment It includes as a Powerful the definition Tool for of Decisionthe goal Makingand scope of the LCA, the inventory analysis Lifephase cycle (LCI), assessments the impact assessment should be phase performed (LCIA) inand full the compliance interpretation, with reporting the corresponding and critical review standard including the limitations, relations between the phases and conditions for the use of choices and ISO 14040:2006. It includes the definition of the goal and scope of the LCA, the inventory analysis options. The LCA technique, the methodologies and the application as such is not standardized, phaseleading (LCI), theto frequently impact assessment insurmountable phase (LCIA)difficulti andes in the comparing interpretation, different reporting LCAs andperformed critical by review includingdifferent the institutions. limitations, The relations problem between is accentuated the phases by the and conflict conditions of interest for the between use of the choices non- and options.disclosure The LCA of process technique, details theby suppliers methodologies and oper andators the of techniques application and as the such need is of not far standardized, reaching leading to frequently insurmountable difficulties in comparing different LCAs performed by different Sustainability 2018, 10, 1482 12 of 19 institutions. The problem is accentuated by the conflict of interest between the non-disclosure of processSustainability details 2018 by, suppliers 10, x FOR PEER and REVIEW operators of techniques and the need of far reaching transparency 12 of 19 as a prerequisite of plausible LCAs. The comparative LCA performed on behalf of the German Environmentaltransparency Protection as a prerequisite Agency of [ 18plausible] has been LCAs conceived. The comparative as a model LCA LCA performed for phosphate on behalf of fertilizers the producedGerman from Environmental fossil and recycled Protection materials. Agency Several[18] has databasebeen conceived flaws haveas a model been revealedLCA for phosphate and corrected fertilizers produced from fossil and recycled materials. Several database flaws have been revealed and full transparency will be provided as soon as the report is published [18]. and corrected and full transparency will be provided as soon as the report is published [18]. The preliminary results of the normalized LCA of phosphate fertilizers on the German market [18] The preliminary results of the normalized LCA of phosphate fertilizers on the German market exhibit[18] two exhibit relevant two environmentalrelevant environmental impacts: impacts: eutrophication eutrophication and human and human toxicity. toxicity. Eutrophication Eutrophication is mainly causedis bymainly applying caused fertilizers by applying to cropland fertilizers and to cropland losing phosphate and losing to phosphate water bodies. to water Long-term bodies. Long-term eutrophication is alsoeutrophication due to phosphogypsum is also due to stacksphosphogypsum directly releasing stacks directly acidic releasing process wateracidic process to rivers water [22, 23to ]riversbut does only marginally[22,23] but does contribute only marginally to the global contribute impact to reflected the global in impact the LCA, reflected if no in long-term the LCA, sensitivityif no long-term analysis is performed.sensitivity The analysis main is contributor performed. toThe the main human contributor toxicity to impact the human category toxicity is cadmiumimpact category (Cd), ais toxic metalcadmium present in(Cd), relatively a toxic highmetal concentrationspresent in relatively in sedimentary high concentrations phosphates. in sedimentary The relevance phosphates. of the two mainThe impact relevance categories of the intwo comparison main impact to categories others is in exhibited comparison in Figureto others9. is exhibited in Figure 9.

FigureFigure 9. LCA 9. LCA normalization normalization of of baseline baseline for for averageaverage P P fertilizers fertilizers sold sold in inGermany Germany [18]. [ 18].

Despite its flaws in revealing the regional impacts of phosphogypsum stacks, regardless if Despite its flaws in revealing the regional impacts of phosphogypsum stacks, regardless if caused caused by accidents [24,25] or by continuous leaching [22,23], LCA is a powerful tool for evaluating by accidentsthe direct [ 24environmental,25] or by continuous impact of options leaching for [impr22,23ovement], LCA in is case a powerful of conflicting tool interests. for evaluating In the the directLCA environmental study, the conflicting impact of optionsinterests forare improvementbetween energy in caseconsumption of conflicting with interests.its corresponding In the LCA study,greenhouse the conflicting gas emissions interests and are huma betweenn toxicity, energy since consumption removing cadm withium its from corresponding phosphate fertilizers greenhouse gas emissionsconsumes andenergy human from fossil toxicity, fuels, since regardless removing if wet cadmiumchemical or from thermochemical phosphate processes fertilizers are consumes used. energyThe from critical fossil question fuels, is regardless whether the if wetadditional chemical use of or energy thermochemical justifies the removal processes of cadmium are used. in The terms critical questionof the is impact whether categories the additional of the LCA. use of energy justifies the removal of cadmium in terms of the impact categoriesAs Figure of 9 the clearly LCA. shows, phosphate processing only marginally (<0.1%) contributes to the global warming potential by greenhouse gas (GHG) emissions. Even if more energy is needed for As Figure9 clearly shows, phosphate processing only marginally (<0.1%) contributes to the global producing controlled release fertilizers or removing cadmium from phosphate rock or phosphoric warming potential by greenhouse gas (GHG) emissions. Even if more energy is needed for producing acid, the impact on greenhouse gas emissions is unlikely to become relevant, since the additional controlledGHG releaseemissions fertilizers remain ormarginal. removing In cadmiumaddition, fromfossil phosphatefuels such rockas natural or phosphoric gas in the acid, study the for impact on greenhousecalcination, gasmay emissions be replaced is by unlikely renewable to becomeenergy such relevant, as concentrated since the solar additional power in GHG the future, emissions remainwhereas marginal. cadmium In addition, accumulated fossil in fuels soils suchwill remain as natural and gasonly in gradually the study be for taken-up calcination, by crops, may be replacedconsequently by renewable increasing energy the suchweekly as human concentrated cadmium solar intake power rate already in the exceeding future, whereas the European cadmium accumulatedFood Safety in soilsAuthority’s will remain (EFSA) and recommendations only gradually (tolerable be taken-up weekly by intake crops, of 2.5 consequently µg/kg body weight) increasing the weeklyfor toddlers, human children cadmium and vegetarians. intake rate According already exceedingto the Scientific the Report European of EFSA, Food individual Safety Authority’s dietary (EFSA)survey recommendations results varied between (tolerable a weekly weekly minimum intake lower of 2.5 boundµg/kg average body weight)of 1.15 to fora maximum toddlers, upper children bound average of 7.84 µg/kg body weight and a minimum lower bound 95th percentile of 2.01 and a and vegetarians. According to the Scientific Report of EFSA, individual dietary survey results varied Sustainability 2018, 10, 1482 13 of 19 between a weekly minimum lower bound average of 1.15 to a maximum upper bound average of 7.84Sustainabilityµg/kg body2018, 10 weight, x FOR PEER and REVIEW a minimum lower bound 95th percentile of 2.01 and a maximum13 of 19 Sustainability 2018, 10, x FOR PEER REVIEW 13 of 19 µ uppermaximum bound 95th upper percentile bound 95th of 12.1 percentileg/kg of body 12.1 µg/kg weight body reflecting weight differentreflecting dietarydifferent habits dietary and habits survey methodologiesandmaximum survey [upper methodologies26]. Figure bound 1095th [26].shows percentile Figure the 10 increaseof shows 12.1 µg/kg the of globalincrease body weight warming of global refl warmingecting potential different potential if applying dietary if applying habits cadmium removalcadmiumand processes,survey removal methodologies a marginalprocesses, [26]. increasea Figuremarginal 10 from showsincrease a verythe from increase low a very basis of globallow of basis only warming of 0.1% only potential of0.1% the of globalifthe applying global impact per citizen.impactcadmium per removal citizen. processes, a marginal increase from a very low basis of only 0.1% of the global impact per citizen.

FigureFigure 10. Global10. Global warming warming potential potential increase increase byby thethe net energy energy effort effort for for cadmium cadmium removal removal by by calcinationcalcinationFigure (rock 10. (rockGlobal decadmiation) decadmiation) warming orpotential solventor solven increase extractiont extraction by the (acid (acid net decadmiation)decadmiation) energy effort [18].for [18 cadmium]. removal by calcination (rock decadmiation) or solvent extraction (acid decadmiation) [18]. A significantA significant reduction reduction of theof the human human toxicity toxicity potentialpotential is is achieved achieved which which has has a tangible a tangible impact impact on theA percentagesignificant ofreduction contribution of the of human phosphate toxicity fert potentialilizers to theis achieved total toxicity which humans has a tangible are exposed impact to. on the percentage of contribution of phosphate fertilizers to the total toxicity humans are exposed to. Theon the results percentage represent of contribution the average oftoxicity phosphate potential fertilizers for people to the livingtotal toxicity in Germany, humans where are exposed more than to. The results represent the average toxicity potential for people living in Germany, where more than 50%The resultsof phosphate represent fertilizers the average in the toxicity market potential are produced for people from livingRussian in phosphateGermany, whererock concentrate more than 50% ofwith50% phosphate ofnegligible phosphate fertilizers cadmium fertilizers in theconcentrations. in marketthe market are producedareIn countriesproduced from wherefrom Russian Russian sedimentary phosphate phosphate rock-based rock rock concentrate concentrate fertilizers with negligibleprevail,with cadmiumnegligible the impact cadmium concentrations. is even moreconcentrations. pronounced. In countries In Thecountries where relevant sedimentarywhere toxicity sedimentary potential rock-based decrease rock-based fertilizers achievable fertilizers prevail, by the impactcadmiumprevail, is eventhe removal impact more isis pronounced.shown even more in Figure pronounced. The 11. relevant The toxicity relevant potential toxicity potential decrease decrease achievable achievable by cadmium by removalcadmium is shown removal in Figure is shown 11. in Figure 11.

Figure 11. Human toxicity potential decrease due to cadmium removal by calcination (rock Figure 11. Human toxicity potential decrease due to cadmium removal by calcination (rock decadmiation) decadmiation)Figure 11. Human or solvent toxicity extraction potential (acid decrease decadmiation) due to [18]. cadmium removal by calcination (rock or solvent extraction (acid decadmiation) [18]. decadmiation) or solvent extraction (acid decadmiation) [18]. Sustainability 2018, 10, 1482 14 of 19

3.6. Circular Principles and Resource Efficiency InSustainability terms of 2018 using, 10, by-x FOR or PEER secondary REVIEW products, the phosphate industry, similar to the entire 14 chemical of 19 industry, is an early adapter of circular principles. In Europe, about 70% of sulfuric acid used for 3.5. Circular Principles and Resource Efficiency rock digestion is secondary (used) acid originating from other processes [18]. The phosphate industry absorbs mostIn terms ammonium of using sulfate by- orcoming secondary as aproducts, by-product the ofphosphate caprolactam industry, production similar asto N-carrierthe entire and the nitro-phosphatechemical industry, process is an early (also adap knownter of as circular Odda principles. process) does In Europe, not generate about 70% waste of sulfuric flows atacid all by used for rock digestion is secondary (used) acid originating from other processes [18]. The phosphate producing nitro phosphoric acid and calcium ammonium nitrate (CAN), the latter being a by-product industry absorbs most ammonium sulfate coming as a by-product of caprolactam production as N- and acarrier widely and accepted the nitro-phosphate nitrogen fertilizer process[ (also27]. However,known as Odda due toprocess) using does very not old generate processes, waste dating flows back to theat 19th all by and producing 20th centuries, nitro phosphoric and the frequentacid and calcium usage of ammonium old production nitrate facilities(CAN), the that latter have being not a been revampedby-product for decades, and a widely there accepted is a significant nitrogen gapfertilizer between [27]. However, the efficiency due to options using very available old processes, and those used indating practice. back to the 19th and 20th centuries, and the frequent usage of old production facilities that Resourcehave not efficientbeen revamped production for decades, processes there facilitate is a significant waste management gap between andthe efficiency a faster transition options to circularavailable principles. and those Phosphate used in processingpractice. offers a variety of options to increase the resource efficiency and separateResource commercially efficient production viable resources processes from facilitate waste waste streams. management Hereafter, and we a discussfaster transition two examples to of lowcircular hanging principles. fruits for Phosphate increased proces materialssing offers and energya variety efficiency of options in to the increase phosphate the resource industry efficiency and some and separate commercially viable resources from waste streams. Hereafter, we discuss two examples more challenging options. of low hanging fruits for increased materials and energy efficiency in the phosphate industry and Resourcesome more efficiency challenging in termsoptions. of phosphate use is determined by P solubilization during digestion and by co-crystallizationResource efficiency in phosphogypsum.in terms of phosphate Energy use is determined efficiency dependsby P solubilization on heat recoveryduring digestion rates from exothermicand by reactionsco-crystallization (sulfur in burning, phosphogypsum. acid neutralization) Energy efficiency and ondepends the heat on heat employed recovery for rates phosphoric from acid concentrationexothermic reactions [18,28 ].(sulfur burning, acid neutralization) and on the heat employed for phosphoric Almostacid concentration 92% of the [18,28]. world’s phosphoric acid processes outside of China operate the Dehydrate (DH, aboutAlmost 76% of92% global of the PA world’s production) phosphoric and acid Hemihydrate processes outside processes of China (HH, operate about the 15% Dehydrate of global PA (DH, about 76% of global PA production) and Hemihydrate processes (HH, about 15% of global PA production), the classical one-crystal processes with P2O5 recovery rates of 95% (DH) and 93% (HH), production), the classical one-crystal processes with P2O5 recovery rates of 95% (DH) and 93% (HH), respectively. The lower recovery rate of the HH process is compensated by a significantly higher P2O5 respectively. The lower recovery rate of the HH process is compensated by a significantly higher P2O5 concentration in the acid—40–46% vs. 26–32%—requiring less steam for water evaporation to the concentration in the acid—40–46% vs. 26–32%—requiring less steam for water evaporation to the usual 54% P O concentration in merchant grade acid (MGA) [29]. At least two proven processes usual 54%2 5P2O5 concentration in merchant grade acid (MGA) [29]. At least two proven processes that that increaseincrease thethe PP recoveryrecovery rates to to 97–98% 97–98% and and produce produce a acleaner cleaner and and dryer dryer phosphogypsum phosphogypsum are are availableavailable and reportedlyand reportedly easily easily implementable implementable with with moderatemoderate CAPEX CAPEX investments: investments: Nissan’s Nissan’s H and H and Prayon’sPrayon’s DA-HF DA-HF processes, processes, using using double double crystallization crystallization and single single filtration filtration according according to the to flow the flow sheet insheet Figure in Figure 12[28 12]. [28].

FigureFigure 12. 12.Prayon Prayon DA-HF DA-HF processprocess flow flow sheet sheet [28]. [28 ]. SustainabilitySustainability 20182018,, 10,, x 1482 FOR PEER REVIEW 1515 of of 19 19

Apart from OCP’s SAFI MP1 and MP2 (Nissan H process) and a few other plants, the described efficiencyApart enhancement from OCP’s SAFIprocesses MP1 andare not MP2 widely (Nissan used, H process) despite and their a fewenvironmental other plants, and the economic described advantagesefficiency enhancement [28]. If the transition processes to a are Circular not widely Economy used, is despitetaken seriously, their environmental industrial implementation and economic ofadvantages higher resource [28]. If theefficiency transition processes to a Circular should Economy become is takena priority. seriously, Having industrial a direct implementation impact on the of phosphatehigher resource recovery efficiency rate, processes the double should crystallizatio become a priority.n processes Having reduce a direct co-crystallization impact on the phosphate of P in phosphogypsumrecovery rate, the and double its water crystallization content from processes close to reduce 20% to co-crystallization 6% thus giving a of very P in good phosphogypsum example for theand interdependency its water content fromof resource close to efficiency 20% to 6% and thus wa givingste management. a very good exampleIn addition, for the these interdependency processes do notof resource cause a efficiencyconflict of and interest—they waste management. just require In addition, revamping these phosphoric processes do acid not plants cause awith conflict some of moderateinterest—they investment just require [30]. revamping phosphoric acid plants with some moderate investment [30]. AA low hanging fruit fruit for energy efficiency efficiency improv improvementement is is enhancing the the heat heat (steam) recovery recovery duringduring sulfuric sulfuric acid acid production. In In conventional conventional sulfuric sulfuric acid acid plants, plants, about about 40% 40% of of the recoverable heatheat is is wasted, wasted, as shown by th thee Sankey diagram in Figure 13.13.

Figure 13. Sankey diagram of heat flows from sulfur conversion [31]. Figure 13. Sankey diagram of heat flows from sulfur conversion [31]. By implementing enhanced heat recovery system (e.g., Outotec’s Heros®), the conversion ® efficiencyBy implementing of sulfur combustion enhanced could heat be recovery increased system from close (e.g., to Outotec’s 58% to 71%, Heros a big), step the in conversion resource efficiency.efficiency ofThe sulfur system combustion produces coulda low-pressure be increased stea fromm of closeabout to10 58% bars to for 71%, constant a big stepuse. inSmart resource heat recoveryefficiency. systems The system do not produces hamper athe low-pressure production steamof sulfuric of about acid 10if shut bars down for constant for maintenance use. Smart [31]. heat recoveryAnother systems example do not for hamper energy the efficiency production by low of sulfuric pressure acid steam if shut recovery down forare maintenance closed loop [steam31]. dryers,Another cutting example the energy for use energy for drying efficiency by by60%, low from pressure 800–1000 steam kWh recovery per ton are of closedwater to loop less steam than 400dryers, kWh. cutting Closed the loop energy steam use dryers for drying are typically by 60%, used from for 800–1000 biomass kWh drying per tonbefore of water its use to as less a fuel. than Outotec400 kWh. has Closed built a looppilot steamdryer dryersfor testing are different typically materials used for biomasscontaining drying up to before80% water. its use Until as anow, fuel. (sewage)Outotec hassludges built and a pilot slurries dryer (e.g., for testing digestion different residues) materials have containingbeen succes upsfully to 80% dried water. to 90–95% Until now,dry matter.(sewage) The sludges CLS dryer and slurriesmay be (e.g.,a valuable digestion option residues) for drying have slurries been successfully and products dried in the to 90–95% phosphate dry industrymatter. The [32]. CLS dryer may be a valuable option for drying slurries and products in the phosphate industryApart [32 from]. materials and energy for direct use in the plant, phosphate ores may contain fluorine, rare earthApart elements from materials (REE), anduranium, energy radium, for direct cadmiu use inm the and plant, other phosphate elements that ores are may transferred contain fluorine, to the productrare earth or elementsthe waste (REE), streams uranium, without radium, having cadmiuma positive andfunctionality. other elements On the that contrary, are transferred some of tothese the componentsproduct or the are waste undesirable streams or without classified having as pollutant a positive that functionality. may hamper Onthe thebeneficial contrary, use some of fertilizers of these orcomponents the recycling are potential undesirable of waste or classified streams, as in pollutant particular that regarding may hamper the use the of beneficial phosphogypsum use of fertilizers [33,34] Inor a the linear recycling economy potential and a of business waste streams, as usual in scenario, particular these regarding resources the use are of extracted phosphogypsum as long as [33 they,34] canIn a be linear sold economyand supplied and ain business response as to usual an appare scenario,nt market these resourcesdemand and are dire extractedctly contribute as long as to they the profits of the phosphate industry. In a Circular Economy, solutions should be sought by joint efforts Sustainability 2018, 10, 1482 16 of 19 can be sold and supplied in response to an apparent market demand and directly contribute to the profits of the phosphate industry. In a Circular Economy, solutions should be sought by joint efforts of larger stakeholder groups forming clusters. Their common task is developing solutions that could bring about mid-term commercial and environmental benefits. Phosphate ore is a relevant resource for uranium with some 20,000 tons globally addressable. Prayon and Union Minière (now Umicore) developed the so-called DEHPA/TOPO two-stage solvent extraction process for recovery of uranium from Moroccan phosphoric acid [35]. The first uranium recovery plant from phosphate ores was operational in Florida in 1976. Prayon successfully recovered uranium from phosphoric acid from 1980 until 1998 in Belgium. When the investment decision was taken, the price for U3O8 was USD 42.00/lb. The plant was closed when the price for U3O8 was USD 10.00/lb. A profitable extraction of uranium from phosphate ores was not possible from these days onwards [35]. Another valuable resource associated with some phosphate ores are rare earth elements (REE). Among others, the ores of the Kirovsky and Kovdorsky mines in the Murmansk region (Russia) contain REE in concentrations apparently making extraction commercially feasible. The Russian fertilizer producer Acron extracted and processed 200 tons of rare earth oxides – Cerium, Lanthanum and Neodymium—from its apatite concentrate. Acron is currently the only Russian industrial producer of REE [18]. Solvent extraction processes are appropriate for extracting REE from phosphoric acid and revenues from two groups of elements—radionuclides and REE may support each other to achieve commercially viable technology developments [36]. The examples for higher phosphorus recovery rates and energy efficiency are arbitrarily selected for demonstration that technology suppliers have solutions for improvement. Other suppliers may have similar improvements and examples must not be understood as a recommendation for the suppliers mentioned above.

4. Conclusions The United Nations—indeed all nations on our planet—have committed themselves to the 17 Sustainable Development Goals and to the Paris Agreement (COP21) to curb greenhouse gas emissions drastically for preventing a temperature increase of more than 2 ◦C. (On 1 June 2017, Donald Trump announced that the United States would withdraw from the COP21 Agreement. According to Article 28 of the Agreement, the earliest possible effective US withdrawal date could be 4 November 2020, four years after the Agreement became effective in the US.) The UN has set the normative framework for sustainable and inclusive development. In this spirit, the European Commission has adopted the Circular Economy Package. If we take this framework seriously—it is highly recommended to do so if we intend to operate within the safe space of our planet—business as usual is not an option. For the first time in industrial history, we have a global and a European framework, albeit not legally binding, for decoupling growth from materials use. The global agreements reflect a shared conviction that, by continuing the unlimited use of natural resources, the conditions for life on our planet will be destroyed. Conditions for life are not exacerbated by scarcity, but by abundance, use of resources to an extent that nature cannot tolerate. In nature, circular principles prevail. Atoms do not disappear, they simply change chemical bonding and physical state. Human interference dissipates and transfers them to places where they cause damage. While burning fuels, we transfer carbon and other greenhouse gases to the atmosphere instead of keeping it in our soils. While producing fertilizers and using them, we dissipate phosphorus and transfer it to aquatic bodies causing eutrophication and killing aquatic life. The fact that nothing disappears, and that nature provides a model for how we should deal with our resources gives rise to optimism. We just need to learn to copy nature, and the Circular Economy, judged from this point of view, is obviously a smart concept. Sustainability 2018, 10, 1482 17 of 19

Investigating the strong and week points in phosphate processing revealed the by-product phosphogypsum disposed of in stacks or still discharged to the ocean being the single most critical issue: it contributes to P losses and eutrophication. A comparative life cycle assessment performed on behalf of the German EPA exhibited two major environmental impacts of phosphate fertilizers: eutrophication and human toxicity. Eutrophication is mainly due to fertilizer application but can be influenced by producing fertilizers which release nutrients in synchrony with plant uptake. New fertilizers and new fertilizing practices must be developed hand in hand to avoid dissipation of P and the transfer of (concentrated) pollutants to feed and food. How LCA can be used to evaluate conflicting options has been demonstrated by comparing the normalized impact of reducing the human toxicity and producing additional greenhouse gas emissions for that purpose. Using some additional energy for producing controlled release fertilizers will probably bring similar results but was not subject of the study. Eventually, several technology options are discussed which do not lead to a conflict of interests and simply need modest CAPEX investments to be implemented, even in existing facilities. These technologies lead to higher phosphorus use efficiencies or to higher energy efficiencies without any negative environmental impacts. Most of these processes are mature and ready for implementation. The good news is that during the last decade we have seen several new facilities using best available technologies. Some include extraction of rare earth elements at industrial scale using technologies that are suitable for targeted separation of a variety of substances. Once in use, value materials as well as pollutants may be extracted. It can be concluded that despite the apparent problems related to phosphate processing, policy makers, academia and industry jointly launch initiatives towards cleaner, more efficient production of products with a lower impact. These initiatives would, however, be more convincing if industry lobbying for higher pollution limits would be replaced by a joint societal commitment to all-inclusive Circular Economy principles.

Author Contributions: L.H. conceived and wrote the paper. F.K. did the Life Cycle Assessment of decadmiation technologies. R.H. did research on waste flows. Funding: This research received no external funding except for the Life Cycle Assessment case study which was funded as part of a comprehensive study by the German Environmental Agency, UFOPLAN research no. 3716 31 330 0. Conflicts of Interest: The authors declare no conflicts of interest.

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