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Phosphorus Circular Economy: Closing Loops through Sustainable Innovation

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A special issue of Sustainability (ISSN 2071-1050). This special issue belongs to the section "Sustainable Engineering and Science".

Deadline for manuscript submissions: closed (15 April 2018) | Viewed by 85068

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Special Issue Editors

Prof. Dr. Gerald Steiner

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Guest Editor

1. Department of Knowledge and Communication Management, Danube-University Krems, Dr. Karl-Dorrek-Straße 30, 3500 Krems, Austria
2. Weatherhead Center for International Affairs (WCFIA), Harvard University, 1737 Cambridge Street, Cambridge, MA 02138, USA
Interests: sustainability-oriented innovation systems/-processes; sustainable resource management; phosphate rock mining; organizational and regional innovation systems; organizational communication
Special Issues, Collections and Topics in MDPI journals

Mr. Bernhard Geissler

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Department for Knowledge and Communication Management, Danube University Krems, Dr.-Karl-Dorrek-Straße 30, 3500 Krems, Austria
Interests: global food security; sustainable phosphate rock mining and management; efficiency and performance benchmarking; operations research; closed-loop supply chain management

Special Issue Information

Dear Colleagues,

The necessary optimization of the predominately complex supply chain requires inevitable understanding of the underlying system dynamics; this holds especially true for the unique characteristics of phosphorus. The finiteness of the primary source phosphate rock requires a transdisciplinary approach in order to generate, utilize, and transfer knowledge between stakeholders. On its own, no discipline will be able to solve the underlying problems of future P supply, therefore, we aim to include the overall supply chain, from extraction, mining, processing, to the use phase. Recycling holds an exceptional position since it is of greater importance for closing potential loops. Therefore, unlike previous works, we will not focus solely on the recycling of sewage sludges, as previous studies show enormous potential, especially during mining and beneficiation processes. Furthermore, we want to emphasize the interrelations between the single phases of the supply chain, particularly the role of market prices and the role of technology which both leading to often unconsidered underlying dynamics. From our perspective innovation will be a key element for technological developments, prices of raw materials and intermediates, and, most importantly, for closing loops all along the supply chain.

Prof. Dr. Gerald Steiner
Mr. Bernhard Geissler
Guest Editors

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Keywords

sustainable phosphorus management
closed-loop supply chains
transdisciplinarity
efficiency
circular economy
innovation

Published Papers (14 papers)

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Editorial

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8 pages, 1637 KiB

Open AccessEditorial

Sustainable Mineral Resource Management—Insights into the Case of Phosphorus

by Gerald Steiner and Bernhard Geissler

Sustainability 2018, 10(8), 2732; https://doi.org/10.3390/su10082732 - 02 Aug 2018

Cited by 7 | Viewed by 4424

Abstract

Although it is among the most abundant elements in Earth’s crust (11th [1]) and water (13th [2]), phosphorus (P) is commonly referred to as “life’s bottleneck”, as “life can multiply until all the
phosphorus is gone, and then there [...] Read more.

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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Research

Jump to: Editorial, Review

13 pages, 383 KiB

Open AccessArticle

A Model for the Optimal Recovery of Multiple Substances from Waste Water with a Focus on Phosphate

by Jan C. Bongaerts

Sustainability 2018, 10(8), 2867; https://doi.org/10.3390/su10082867 - 13 Aug 2018

Cited by 2 | Viewed by 2905

Abstract

In recent times, the issue of a “Phosphate Peak” has entered the academic debate and it is widely present in social media. Arguments in favour and against are similar to those mentioned in the much earlier debate on the “Oil Peak”. However, whereas the “Oil Peak” is supply driven, the “Phosphate Peak”, if at all, is demand driven. In contrast with oil, most of which is chemically transformed in CO₂, vapor and other constituting elements, phosphate is not “consumed” during its primary use as a fertilizer. Hence, whilst phosphate rock, from which phosphate is mined, is a depletable resource, phosphate itself is potentially recyclable and re-usable. Research on the technologies for such a recovery is manifold and, specifically, efforts are spent on waste water as a source of phosphate. This, if successful, could lead to a changing perception of waste water treatment plants as a set of backstop technologies to eliminate an environmental problem into a “secondary liquid mine” from which phosphate, but not only phosphate, could be extracted for re-use. Hence, for that purpose, an economic model of efficient extraction of phosphate and other elements from waste water in a waste water treatment plant could give guidance to operators. This paper presents such a model describing the optimal simultaneous extraction of several elements, including phosphate, from a “secondary liquid mine”. The elements are assumed to be present in given proportions (ratios) in this “mine” and the model shows that these ratios have an impact on the optimal extraction path and on resulting “implicit” shadow pricing rules to be adopted by the waste water treatment plant operator. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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17 pages, 287 KiB

Open AccessArticle

Concentrated Phosphorus Recovery from Food Grade Animal Bones

by Edward Someus and Massimo Pugliese

Sustainability 2018, 10(7), 2349; https://doi.org/10.3390/su10072349 - 06 Jul 2018

Cited by 36 | Viewed by 4478

Abstract

Disrupted nutrient recycling is a significant problem for Europe, while phosphorus and nitrogen are wasted instead of being used for plant nutrition. Mineral phosphate is a critical raw material, which may contain environmentally hazardous elements such as cadmium and uranium. Therefore, phosphorus recovery from agricultural and food industrial by-product streams is a critically important key priority. Phosphorus recovery from food grade animal bone by-products have been researched since 2002 and a specific zero emission autothermal carbonization system, called 3R, has been developed in economical industrial scale, providing the animal bone char product (ABC) as output. Different animal bone by-products were tested under different conditions at 400 kg/h throughput capacity in the continuously operated 3R system. Different material core treatment temperatures (between >300 °C and <850 °C) were combined with different residence times under industrial productive processing conditions. It was demonstrated that material core treatment temperature <850 °C with 20 min residence time is necessary to achieve high quality ABC with useful agronomic value. The output ABC product has concentrated >30% phosphorus pentoxide (P₂O₅), making it a high quality innovative fertilizer. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

19 pages, 2880 KiB

Open AccessArticle

Transition of the Swiss Phosphorus System towards a Circular Economy—Part 2: Socio-Technical Scenarios

by Michael Jedelhauser, Jonas Mehr and Claudia R. Binder

Sustainability 2018, 10(6), 1980; https://doi.org/10.3390/su10061980 - 13 Jun 2018

Cited by 21 | Viewed by 4377

Abstract

A transition towards a circular economy of phosphorus (P) in Switzerland is a multi-faceted challenge as P use is subject to a variety of influencing factors comprising policy interventions, consumption trends, or technological innovations on different spatial scales. Therefore, scenarios for P use that take into account both the social and the technical dimension of change are needed for investigating possible pathways of a transition towards more sustainable P futures. Drawing on the multi-level perspective of transition theory, we develop scenarios on the landscape level, i.e., a balanced and healthy human diet, on the regime level, i.e., P recovery from sewage sludge (ash) and meat and bone meal, and on the niche level, i.e., urine separation. Based on the P system of the year 2015, we assess the quantitative implications of the scenarios for the Swiss P system. While scenario 1 mainly affects the agricultural system by reducing the overall P throughput, scenario 2 significantly changes P use in waste management, because P losses to landfills and cement plants decrease and the production of secondary P increases. Scenario 3 shows little quantitative impact on the national P system. From a qualitative transition perspective, however, urine separation entails fundamental socio-technical shifts in the wastewater system, whereas P recovery from sewage sludge (ash) represents an incremental system adaptation. The combination of flow- and transition-oriented research provides more general insights into how a circular economy of P can be reached. Furthermore, the analysis of P recycling scenarios reveals that transition processes in Switzerland are embedded in a global resource economy. Thus, a sole focus on concepts of national P self-sufficiency and the reduction of Switzerland’s P import dependency tend to fall short when analysing the economisation of secondary P materials in the face of transnational resource flows and markets. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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14 pages, 899 KiB

Open AccessArticle

Bridging Gaps in the Agricultural Phosphorus Cycle from an Animal Husbandry Perspective—The Case of Pigs and Poultry

by Michael Oster, Henry Reyer, Elizabeth Ball, Dario Fornara, John McKillen, Kristina Ulrich Sørensen, Hanne Damgaard Poulsen, Kim Andersson, Daniel Ddiba, Arno Rosemarin, Linda Arata, Paolo Sckokai, Elizabeth Magowan and Klaus Wimmers

Sustainability 2018, 10(6), 1825; https://doi.org/10.3390/su10061825 - 01 Jun 2018

Cited by 22 | Viewed by 6878

Abstract

Since phosphorus (P) is an essential element for life, its usage and application across agricultural production systems requires great attention. Monogastric species such as pigs and poultry can significantly contribute to global food security but these animals remain highly dependent on the supply of mineral inorganic P in their feeds. Pig and poultry, which represent 70% of the global meat production, are also major P excretors and thus represent important sources of environmental P inputs. Balancing the P cycle within farming systems is crucial to achieve P sustainable and resilient livestock production. Therefore, the interconnection of animal feed, livestock farming, manure, and soil/aquatic ecosystems requires multidisciplinary approaches to improve P management. With regard to a sustainable agricultural P cycle, this study addresses aspects of feeding strategies and animal physiology (e.g., phase feeding, P conditioning, liquid feeding, phytase supplementation, genetics), soil agroecosystems (e.g., P cycling, P losses, P gains), reuse and recycling (e.g., manure, slaughter waste), measures of farmers’ economic performance (e.g., bio-economic models), and P governance/policy instruments (e.g., P quota, P tax). To reconcile the economic and ecological sustainability of animal husbandry, the strategic objective of future research will be to provide solutions for a sufficient supply of high-quality animal products from resource-efficient and economically competitive agro-systems which are valued by society and preserve soil and aquatic ecosystems. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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29 pages, 3879 KiB

Open AccessArticle

Commercial African Catfish (Clarias gariepinus) Recirculating Aquaculture Systems: Assessment of Element and Energy Pathways with Special Focus on the Phosphorus Cycle

by Sebastian Marcus Strauch, Lisa Carolina Wenzel, Adrian Bischoff, Olaf Dellwig, Jan Klein, Andrea Schüch, Berit Wasenitz and Harry Wilhelm Palm

Sustainability 2018, 10(6), 1805; https://doi.org/10.3390/su10061805 - 30 May 2018

Cited by 37 | Viewed by 9560

Abstract

The reuse of effluent waters and sediments from African catfish (Clarias gariepinus) recirculation aquaculture systems requires a deeper understanding of the nutrient and energy flows and material pathways. Three semi-commercial systems, differing in stocking density, were sampled for nutritive and pollutant elements of the input- (tap water, feed) and output pathways (fillet, carcass, process water, sediments) by ICP-OES/MS and calorimetry. Highly water-soluble elements, e.g., potassium, accumulated in the water, whereas iron, copper, chromium and uranium where found in the solids. Feed derived phosphorous was accounted for, 58.3–64.2% inside the fish, 9.7–19.3% in sediments, and small amounts 9.6–15.5% in the process waters. A total of 7.1–9.9% of the feed accumulated as dry matter in the sediments, comprising 5.5–8.7% total organic carbon and 3.7–5.2% nitrogen. A total of 44.5–47.1% of the feed energy was found in the fish and 5.7–7.7% in the sediments. For reuse of water and nutrients in hydroponics, the macro-nutrients potassium, nitrate, phosphorus and the micro-nutrient iron were deficient when compared with generalized recommendations for plant nutrition. Low energy contents and C/N-ratio restrict the solely use of African catfish solids for biogas production or vermiculture. Using the outputs both for biogas supplement and general fertilizer in aquaponics farming (s.l.) (combined with additional nutrients) appears possible. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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17 pages, 1077 KiB

Open AccessArticle

Achieving Sustainable Phosphorus Use in Food Systems through Circularisation

by Paul J. A. Withers, Donnacha G. Doody and Roger Sylvester-Bradley

Sustainability 2018, 10(6), 1804; https://doi.org/10.3390/su10061804 - 30 May 2018

Cited by 43 | Viewed by 5905

Abstract

The notion of a phosphorus (P) circular economy provides the philosophy, framework, and opportunity to enable food production systems to become more efficient, sustainable, and resilient to a future P scarcity or sudden price shock. Whilst P recovery and recycling are central strategies for closing the P cycle, additional gains in environmental performance of food systems can be obtained by further minimising the amounts of P (a) introduced into the food system by lowering system P demand and (b) lost from the system by utilising legacy P stores in the landscape. This minimisation is an important cascading component of circularisation because it reduces the amounts of P circulating in the system, the amounts of P required to be recycled/recovered and the storage of unused P in the landscape, whilst maintaining agricultural output. The potential for circularisation and minimisation depends on regional differences in these P flow dynamics. We consider incremental and transformative management interventions towards P minimisation within circular economies, and how these might be tempered by the need to deliver a range of ecosystem services. These interventions move away from current production philosophies based on risk-averse, insurance-based farming, and current consumption patterns which have little regard for their environmental impact. We argue that a greater focus on P minimisation and circularisation should catalyse different actors and sectors in the food chain to embrace P sustainability and should empower future research needs to provide the confidence for them to do so without sacrificing future regional food security. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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19 pages, 282 KiB

Open AccessArticle

An Assessment of the Drivers and Barriers for the Deployment of Urban Phosphorus Recovery Technologies: A Case Study of The Netherlands

by Marissa A. De Boer, Anjelika G. Romeo-Hall, Tomas M. Rooimans and J. Chris Slootweg

Sustainability 2018, 10(6), 1790; https://doi.org/10.3390/su10061790 - 29 May 2018

Cited by 49 | Viewed by 5875

Abstract

Phosphorus (P), being one of the building blocks of life, is essential for a multitude of applications, primarily for fertilizer usage. Sustainable management of phosphorus is becoming increasingly important in light of adverse environmental effects, ambiguous reserves, increasing global demand and unilateral dependence. Recovery of phosphorus from the biggest loss stream, communal wastewater, has the potential to tackle each of these problems. The implementation of phosphorus recovery technologies at wastewater treatment plants is not widespread, despite prolonged efforts primarily done by researchers over the past decade. This study aimed to assess the drivers and barriers of a phosphorus recovery transition. Several key stakeholders involved in this transition in The Netherlands were interviewed. The Netherlands was taken as a case study, since it serves as a frontrunner in the implementation of phosphorus recovery technologies. This study shows that the main barriers from the point of view of fertilizer companies are the different and unclear characteristics of the phosphorus recovery product struvite compared to common fertilizers. Moreover, the end-of-waste status of struvite is mentioned as a prominent barrier for a phosphorus transition, since it hinders free market trade. Many water boards indicate that the main barrier is the high investment cost with an uncertain return on investment for onsite struvite recovery processes. The specified main driver for water boards for onsite struvite phosphorus recovery technology is the reduction of maintenance costs, and for phosphorus recovery from sewage sludge ash, the low organic pollutant in the P recovery product. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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15 pages, 403 KiB

Open AccessArticle

Modeling Global Trade in Phosphate Rock within a Partial Equilibrium Framework

by Nikolay Khabarov and Michael Obersteiner

Sustainability 2018, 10(5), 1550; https://doi.org/10.3390/su10051550 - 14 May 2018

Cited by 4 | Viewed by 3455

Abstract

Against the background of combined population and consumption growth, the global sustainable development agenda foresees limits to the expansion of agricultural land. The application of fertilizer is necessary to replenish soil nutrients and keep crop yields high. Phosphate rock (PR) is the main raw material for the production of commercial phosphorus fertilizers. The international PR market is highly concentrated in terms of reserves and supply: a few countries export the major share of all PR traded globally. As many countries are highly dependent on phosphorus import, the modeling of international PR trade and thus exploration of what-if scenarios is of great interest. For modeling purposes, we employ the partial equilibrium framework. The model is driven by a subset of the United Nations (UN) Comtrade database at a yearly time step spanning the period 1997–2016. The only inputs to the model are slope coefficients of demand–supply curves. The transportation costs are internalized by creating a costs ensemble on the basis of historical data. While reasonably sensitive to its inputs, the model fits very well to reported global annual traded quantities and prices and considerably improves per-trade-partner quantity estimates as compared to simple period-averaging approaches. This is the first application of a partial equilibrium approach to global PR market modeling, including validation. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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19 pages, 4262 KiB

Open AccessArticle

Phosphorus Processing—Potentials for Higher Efficiency

by Ludwig Hermann, Fabian Kraus and Ralf Hermann

Sustainability 2018, 10(5), 1482; https://doi.org/10.3390/su10051482 - 08 May 2018

Cited by 31 | Viewed by 9062

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. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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17 pages, 1324 KiB

Open AccessArticle

Transition of the Swiss Phosphorus System towards a Circular Economy—Part 1: Current State and Historical Developments

by Jonas Mehr, Michael Jedelhauser and Claudia R. Binder

Sustainability 2018, 10(5), 1479; https://doi.org/10.3390/su10051479 - 08 May 2018

Cited by 32 | Viewed by 4831

Abstract

Current phosphorus (P) use in European countries is highly dependent on mineral P imports and not sustainably managed. In order to identify and implement measures for sustainable P management, a comprehensive understanding of national P flows and stocks and their temporal dynamics is essential. We conduct a substance flow analysis (SFA) of the Swiss P system of the year 2015, and study the dynamics of the national P system by looking into its development since 1989. Furthermore, we investigate how political-legislative interventions affected the P system during this period. The results show that between 1989 and 2015, the P efficiency in Swiss agriculture increased from 59% to 94%, mainly due to a considerable reduction of fertilization in the agricultural subsystem. At the same time, Switzerland's P import dependency decreased from 33% to 24% between 1989 and 2002 because of a reduction of mineral fertilizer import and use. Between 2002 and 2015, the import dependency stagnated because further improvements in P use efficiency in agriculture were outweighed by a decrease of P recycling and an increase of P losses in the waste management system. By embedding these temporal dynamics in their political-legislative context, we found that top-down interventions such as incentives for a balanced nutrient budget in agriculture, restrictions of the use of animal by-products in the agri-food system or the ban of direct sewage sludge recycling in agriculture significantly affected and shaped the national P system. Our analysis provides profound quantitative and qualitative insights into past and present P management in Switzerland and is followed by part 2 of the paper, where we analyze possible future pathways of P management. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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18 pages, 21472 KiB

Open AccessFeature PaperArticle

Phosphorus Supply Chain—Scientific, Technical, and Economic Foundations: A Transdisciplinary Orientation

by Michael C. Mew, Gerald Steiner and Bernhard Geissler

Sustainability 2018, 10(4), 1087; https://doi.org/10.3390/su10041087 - 05 Apr 2018

Cited by 29 | Viewed by 10370

Abstract

Natural mineral resources, such as phosphates, represent global assets of tremendous economic value to stakeholders. Given its special characteristics and its essentiality for all life on Earth, phosphorus (P) bears additional value to society as it is both indispensable and not substitutable. Most peers in the field, as well as those coming to phosphorus research, are aware of the complex underlying system dynamics of the P supply chain. In view of the manifold problems involved, scientists from various disciplines as well as practice need to find (new) ways to generate, utilize, transfer, and integrate knowledge. This manuscript serves as a best-practice example as it originates from a long-lasting science/practice collaboration and is the result of a mutual learning process. As a cornerstone of the special issue on “Phosphorus Circular Economy: Closing Loops through Sustainable Innovation” we provide state-of-the-art scientific knowledge as well as practical expert insights from the perspectives of geology, technology, economics, and policy making. This manuscript shall help scientific peers, the public, respective companies, and policymakers to address the issue of sustainable phosphorus management. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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Review

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18 pages, 593 KiB

Open AccessReview

Fertilizer Effect of Phosphorus Recycling Products

by Wilhelm Römer and Bernd Steingrobe

Sustainability 2018, 10(4), 1166; https://doi.org/10.3390/su10041166 - 13 Apr 2018

Cited by 42 | Viewed by 6042

Abstract

Between 2004 and 2011 the German Government funded 17 different projects to develop techniques of phosphorus recycling from wastewater, sewage sludges, and sewage sludge ashes. Several procedures had been tested, such as precipitation, adsorption, crystallization, nano-filtration, electro-dialysis, wet oxidation, pyrolysis, ion exchange, or bioleaching. From these techniques, 32 recycling products were tested by five different institutes for their agronomic efficiency, that is, their plant availability, mainly in pot experiments. This manuscript summarizes and compares these results to evaluate the suitability of different technical approaches to recycle P from wastes into applicable fertilizers. In total, 17 products of recycled sewage sludge ashes (SSA), one meat and bone meal ash, one sinter product of meat and bone meal, one cupola furnace slag, nine Ca phosphates from crystallization or from precipitation, Seaborne-Ca-phosphates, Seaborne-Mg-phosphate, and 3 different struvites were tested in comparison to controls with water soluble P, that is, either single super phosphate (SSP) or triple super phosphate (TSP). Sandy and loamy soils (pH: 4.7–6.8; CAL-P: 33–49 ppm) were used. The dominant test plant was maize. Phosphorus uptake from fertilizer was calculated by the P content of fertilized plants minus P content of unfertilized plants. Calculated uptake from all products was set in relation to uptake from water soluble P fertilizers (SSP or TSP) as a reference value (=100%). The following results were found: (1) plants took up less than 25% P in 65% of all SSA (15 products); (2) 6 products (26%) resulted in P uptake of 25 and 50% relatively to water soluble P. Only one Mg-P product resulted in an uptake of 67%. With cupola furnace slag, 24% P uptake was reached on sandy soil and nearly the same value as TSP on loamy soil. The uptake results of Ca phosphates were between 0 and 50%. Mg-P products from precipitation processes consistently showed a better P supply in relation to comparable Ca-P compounds. With struvite the same P uptake as for water soluble P was reached. The fertilizer effect of the tested P recycling products can clearly be differentiated: TSP = struvite > Mg-P = sinter-P > Ca-P, cupola-slag > thermally treated sewage sludge ashes > meat-and-bone meal ash = Fe-P. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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22 pages, 3128 KiB

Open AccessReview

What Is the Optimal and Sustainable Lifetime of a Mine?

by Friedrich-Wilhelm Wellmer and Roland W. Scholz

Sustainability 2018, 10(2), 480; https://doi.org/10.3390/su10020480 - 11 Feb 2018

Cited by 15 | Viewed by 5143

Abstract

The first stage of the circular economy, mining, is examined from the perspective of sustainability. The authors discuss how to maximize the use of phosphate rock, a primary commodity. To attract investment capital in a market economy system, a mine has to operate profitably, i.e., its lifetime must be optimized under economic conditions, for example, according to Taylor’s Rule. From a sustainability perspective, however, the lifetime should extend as long as possible and the grades mined be as low as possible. The authors examine methods for optimizing a mine’s lifetime under economic conditions according to practical experience and learning effects to optimize exploration and exploitation. With the condition of sustainability, a recently developed concept of cut-off grade for a layered phosphate deposit is examined and considerations for prolonging a mine’s lifetime are discussed. As there are big losses from the current and potential future value chains above and below the current cut-off grade, we argue that the losses and use efficiency of phosphorus are key parts of a circular economy. Full article

(This article belongs to the Special Issue Phosphorus Circular Economy: Closing Loops through Sustainable Innovation)

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