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URINE: A VALUABLE
PHOSPHORUS SOURCE
Waterless urinals (Mediamatic, n.d.)
To what extent can the application of struvite fertilizers in the
Netherlands form a solution to phosphorus depletion?
Thomas Budie, Mandy Fit, Julie Loyson & Anne Twaalfhoven University of Amsterdam; December 18th 2015 Word count: 8086 (excluding: Table of Content, Tables and Appendix) Supervisor: Njal van Woerden
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3 INHOUD ABSTRACT ... 4 INTRODUCTION ... 5 METHODS ... 7 THEORETICAL FRAMEWORK ... 9 RESULTS ... 13 Chapter 1: Technical possibilities ... 13 1.1.1 Different methods of recovering phosphorus from urine ... 13 1.1.2 Chemical Precipitation vs. Biological Removal ... 13 1.1.3 Central vs Decentral Recovery ... 14 1.2. Recovery and fertilization potential of struvite ... 15 1.2.1 Properties of struvite ... 15 1.2.2 Cost efficiency ... 16 1.3 Sufficiency of struvite fertilizers ... 17 Chapter 2: The Dutch practice ... 23 2.1 The business potential of struvite fertilizers ... 23 2.1.1 The market as governing source ... 23 2.1.2 Business behind phosphorus recycling ... 24 Chapter 3: Societal change ... 28 3.1 A political transition ... 28 3.1.1 The multi-level perspective: focus on symbiosis and timing ... 28 3.1.2 The multi-level perspective on phosphorus use ... 29 CONCLUSIONS & RECOMMENDATIONS ... 33 DISCUSSION ... 36 REFERENCES ... 38 APPENDIXES ... 45 Appendix 1: Personal communication with Alex Veltman (Waternet) ... 45 Appendix 2: Personal communication with Aalke de Jong (Waternet) ... 66 Appendix 3: Interview with Nico Elzinga (Desah) ... 69
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ABSTRACT
Global phosphorus mines are reaching peak production rates. A mondial phosphorus deficit may be approaching sooner than later. Based on the notion that current linear production systems should be re-thought according to industrial ecology, in which a minimum of materials is lost, this article argues for a more circular use of phosphorus. This could be accomplished through the recovery of phosphorus from urine by the precipitation of struvite. This article questions to what extend the struvite fertilizers in the Netherlands form a solution to phosphorus depletion. This question was addressed by taking an interdisciplinary approach. Through comparative literature studies and interviews with different stakeholders the following conclusions were drawn; a) Struvite is a high quality fertilizer and its production is technically feasible. b) Struvite is not yet established on national and international markets. c) Societal and governmental networks should work symbiotically to initiate a transition towards the implementation of struvite as to create a sustainable phosphorus cycle.
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INTRODUCTION
Setting the scene
Phosphorus is an essential element for all forms of life (Pierrou, 1976). Even so, it is a limiting nutrient for plant growth and is thus an important ingredient of many fertilizers (Cordell & White, 2011).
Naturally, phosphorus circulates between soils and biota (Pierrou, 1976; Fillipelli, 2002). However, this natural cycle was dramatically altered after the Green Revolution, when commercial fertilizers were perfected and applied in great amounts (Filippelli, 2002; Cordell & White, 2011). The additional phosphorus from phosphate mines used in fertilizers has at least doubled the natural influx (Fillipelli, 2002; Bouwman et al., 2009). This has led to severe environmental destruction including the depletion of arable soils, severe eutrophication and coastal dead zones (Cordell & White, 2011; Elser & Bennett, 2011). Nevertheless, global food security has become largely dependent on phosphate fertilizers.
Global phosphate reserves are predicted to reach peak production levels within decades (Cordell & White, 2011). This is alarming, as phosphate rock is non-renewable on human timescales and substitutes simply do not exist (Cordell & White, 2011).
Presently, universal policies and guidelines on the governance of phosphate reserves are non-existent (Cordell & White, 2011; Elser & Bennett, 2011). Phosphate rock reserves are rare. Morocco, the United States and China own the most significant mines (FAO, 2004). The fact that these mines are governed by only a few nations may eventually cause geopolitical conflicts (Cordell & White, 2011; Elser & Bennett, 2011). Hence, it is urgent that countries find ways to become self-sufficient in their phosphorus provision.
Clearly, the world's current phosphorus consumption needs to be revised. A promising solution towards a more circular use of phosphorus lies in (human) wastewater treatment. Only 1% of wastewater is urine, yet urine contains over 50% of the phosphors present in sewage sludge (Wilsenach et al., 2006). Phosphorus can easily be extracted from urine by crystallizing it to struvite minerals, which can effectively be applied as fertilizer (Shu et al., 2006; Childers
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et al., 2011; Rahman et al, 2013). Several pilot studies have proven struvite retention from wastewater treatments to be technically and economically feasible (Shu et al., 2006; Brittion et al., 2007; Childers et al., 2011)
Presently, only the wastewater treatment plant (WWTP) of Amsterdam is recovering struvite from sewage water on a large scale. In current Dutch policies and regulations, sewage is considered a waste product rather than a potential source of valuable nutrients. However, several small scale projects are emerging. Here, urine is separated at its source by the use of diverting toilets allowing struvite production on site. The question remains whether such methods are efficient and will eventually amend the bigger issue.
Research Aim & Structure of the Report
By taking an interdisciplinary approach, we aim to determine how a transition can take place from a linear system to a circular use of phosphorus. This report will answer the question as to what extent the application of struvite fertilizers can be a part of the solution to phosphorus depletion. The question will be assessed using perspectives of biology, earth sciences, political science and business administration. The Dutch system will be the main point of focus, although general conclusions may be interpretable for other nations as well. First of all, the research methods will be briefly outlined. In the theoretical framework, we elaborate on the integrative theory of industrial ecology as it reflects the fundamental principle of our research and the common ground for the four different disciplines. Then, other relevant theories from all disciplines are discussed. Using insights from all four disciplines, the sub-questions as listed in table 1 will be answered. In which, subquestion 1.1 to 1.3 comprises an overview of what is technically and ideally possible. Next, subquestion 2.1 describes the current practice in the Netherlands, while subquestion 3.1 analyses the mismatch between technical possibilities and practice, and how these can be met. Finally, the interdisciplinary results will be combined in order to evaluate the significance and applicability of struvite fertilizers in the Netherlands, as a solution to phosphor depletion.
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METHODS
Scope
The aim of the research is to understand to what extent the application of struvite fertilizers in the Netherlands can form a solution to phosphorus depletion. The Netherlands already has an advanced water treatment system with multiple possibilities for phosphorus recovery. Putting the focus on national level allows for a more detailed approach and will provide more practical conclusions. However, general conclusions can still be applicable to other (western) nations with similar sewage systems.
Furthermore, there are multiple solutions needed to tackle the problem of phosphorus depletion, such as more responsible fertilizer use on the land. Therefore the aim of this research is not only to discuss the potential, but as well the limitations of struvite fertilizers in solving the depletion.
Research Design
The research design will involve a mixed-methods approach, with multi- trans- and interdisciplinary approaches. Table 1 provides an overview of the sub-questions and the methods. The subsub-questions will partly be addressed by literature study, combining insights from different disciplines and outbalance these in interdisciplinary conclusions.
Furthermore, additional interviews have been held two experts that work with the largest project for struvite fertilizers in the Netherlands: Fosvaatje by the wastewater treatment company Waternet in Amsterdam. The first expert was Alex Veltman, how is a chemical engineer that closely involved in the project. The second expert is Aalke de Jong, that is an expert on jurisdictions of struvite. Additionally, an interview was held with Nico Elzinga, process engineer at Desah: a consultancy company that is specialized in sustainable sanitation. The interviews had the form of an unstructured interview, in order to leave space for new topics to come up during the conversation (Walliman, 2010). The complete interviews can be found in the appendix (1, 2 and 3). This resulted in quantitative data about the current state of urine recycling in the Netherlands, as well as qualitative data on the experiences and views of actors. Communication
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with stakeholders from outside the academic world and the integration of stakeholder values and academic knowledge will give research a transdisciplinary character.
Finally, an important part of the research will consist of calculating the potential of struvite recovery from wastewater and separated urine in meeting the fertilizer demand of the Netherlands. This in particular is an integrative method because the insights from literature study and interviews will be integrated for an assessment of different forms of implementation of struvite fertilizers.
Chapter Subquestion Methods
Technical opportunities
1.1. What are different methods of recovering phosphorus from urine?
Literature study / interviews
1.2. How useful is struvite in terms of recovery and fertilization?
Literature study / interviews
1.3. To what extent could the Netherlands produce enough phosphorus from wastewater or separated urine to meet its fertilizer demand? Quantitative assessment / Literature study / interviews The Dutch practice
2.1. What could be the influence of businesses in phosphorus recycling? What are the barriers and how can they be overcome?
Literature study / interviews
Societal change
3.1. Which type of transition will most likely overcome political barriers for the application of struvite fertilization?
Literature study / interviews
Table 1: Subquestions and their methods.
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THEORETICAL FRAMEWORK
Creating common ground: industrial ecology & circular thinking
The disciplines of Biology, Earth Sciences, Politics and Business meet in the concept of Sustainable Development. Sustainable Development is regarded as an intrinsically interdisciplinary term, as it is composed of environmental, technological, societal and economical dimensions (Despeisse et al., 2012). Due to the increased realization of the limited nature of the earth’s resources, sustainable development has gained a prominent position in business practices and industrial designs (Despeisse et al., 2012).
In order to create industrial systems that are self-sustainable and environmentally friendly the concept of Industrial Ecology (IE) has been suggested. In IE, notions of the natural sciences are applied to industrial and societal systems. It is the perception that, ideally, industrial systems should function like ecosystems, in which material flows are naturally balanced and resource inputs and waste outflows are minimized (Ehrenfeld, 2000; Despeisse et al., 2012). According to Ehrenfeld (2000), IE has the potential to shape paradigmatic thinking. It shall be the fundamental principle in the transition towards a system of closed material flows in which concepts of Cradle to Cradle and Circular Economy have become the norm.
Having emerged from multiple disciplines, the discipline of IE has been used as an overarching guideline to this research. We analyse phosphorus material flows and aim to identify possibilities for recycling. Sub-questions 1-3 in particular deal with the different methods of urine recycling and discuss to what extend these methods can establish a minimum mineral loss. Additionally, it is noted that a transition towards a self-sustainable system can only be accomplished when waste products are no longer regarded as waste. In sub-questions 4 and 5 political and business insights are used as to depict what structural barriers need to be overcome in order to accelerate a transition towards a lucrative market for struvite fertilizers.
Conclusively, integration of the different disciplinary insights will provide a more holistic and precise overview of the complex phosphorus issue.
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The bio-chemical phosphorus cycle & anthropogenic alteration
Phosphorus recovery from urine builds on the theory that in natural, undisturbed systems, the flow of phosphorus is cyclic and a only a minimum share of the mineral is lost.
In short; soluble phosphorus is freed from apatite minerals in acidic conditions and can subsequently be utilized by plants and microorganisms (Smeck, 1985). Once phosphorus is taken up by a plant it is assimilated in organic compounds (Smeck, 1985; Fillipelli, 2002). Eventually, this organic phosphorus is returned to soil in plant and animal residues where it can be used again.
This cycle has been disturbed dramatically. Due to unsustainable land use and the largely increased influx of phosphorus through fertilizers, large amounts of the mineral are lost in sinks and will no longer be available for human purposes (Bouwman et al., 2009, Cordell et al., 2009; Cordell & White, 2011). This paper argues that the cyclic flow of phosphorus should be restored so that losses are kept to a minimum and an actual phosphorus deficit is prevented.
Peak phosphorus
In 1956, M. King Hubbert forecasted a decline in U.S. oil production around 1970 by using his bell-shaped Hubbert curve. Eventually, a peak occurred in 1971, but recent discovered resources resulted in a production rebound and thus challenged the theory (Patterson, 2015).
For the same reason, this model is only applicable for phosphorus availability to a certain extent. The preliminary insecurities are the referred reserves, resources and (geo)potential resources (Scholz & Wellmer, 2013). It smooths the past historic production in order to create a symmetric curve and an estimation of the future recoverable resources (Wellmer, 2008).
Nevertheless, the theory itself is useful as it says that extraction of phosphorus results in investments and thus, a higher extraction rate. Eventually, this will lead to the decline of phosphorus concentrations until economic infeasibility/physical depletion (Singer & Menzie, 2010). Consequently, food insecurity or extreme high food prices follow.
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Neoclassical economics
The basis of the market system does not acknowledge the finite nature of non-renewable resources, since greater depletion and consumption is seen as a benchmark for success (Cordell and White, 2011). Rather, it is based on the principles of neoclassical economics that assume that nonrenewable resource scarcity leads to a price rise, which will in turn trigger new investments and fuel technological innovation (Ayres, 2007). When describing the current Dutch practice and possibilities for societal change, it is useful to acknowledge that Neoclassical economics do not recognize a limit to growth and is therefore is in conflict with circular economics, which operates within our planetary boundaries (Daly, 1992).
However, organizations can also respond by recognizing new business opportunities (Barney, 1995). In the case of phosphorus, growing scarcity creates
economy of scale for the exploitation of recovery possibilities and niche
innovations for businesses, especially phosphorus-reliant industries (Shu et al., 2006). The economic feasibility of crystallising struvite can be tested through an evaluation of influences (Porter, 2008).
The Multi-Level Perspective on transitions
The Multi-Level Perspective (MLP) offers an analytical framework by which socio-technological transitions like the application and legislation of struvite fertilization can be analysed (Geels, 2002). Within the framework, socio-technological transitions are seen as a rearrangement of the structures of society. The MLP is different and more comprehensive than top-down or stakeholder management approaches, because the MLP takes into account the whole system of society and acknowledges the power of social structures such as routines, relationships and cultural values. Transition management can solely strategically try to manage these structures to find the best suited solutions.
Figure 1 displays how a previously relatively constant regime of social structures can be disrupted and transformed by landscape pressures and niche-innovations.
The MLP allows us to categorize actors and practices involved in phosphorus use, according to their position in the framework: niche, regime or
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landscape. Furthermore, the MLP stresses the importance of the symbiotic potential between regime and niche-innovators, which will be further discussed under subquestion 3.1.
Figure 1. Multi-level perspective on transitions (adapted from Geels, 2002). Landscape pressures are long-term, macro-level, developments that create new societal and technical demands. Niche-innovations are specific networks of new technologies, practices and thoughts that meet these new societal demands.
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RESULTS
CHAPTER 1: TECHNICAL POSSIBILITIES
1.1.1 DIFFERENT METHODS OF RECOVERING PHOSPHORUS FROM URINE
A number of strategies exist in order to reduce phosphorus use such as reductions in food waste and phosphorus containing detergents. Furthermore, application of no-till agriculture and bio-fertilizers could lead to a lower fertilizer requirement. This is because, respectively, it leads to less runoff and improved phosphorus release/uptake in the rhizosphere (plant root zone) (Koppelaar & Weikard, 2013).
Recycling options are food-waste recycling and wastewater treatment. This research concerns wastewater treatment, with the treatment of urine in particular. Currently, the most widely applied method of phosphorus recovery from this mineral-rich source is through struvite crystallization.
1.1.2 CHEMICAL PRECIPITATION VS. BIOLOGICAL REMOVAL
At a global level, a mere 10% of phosphorus from human waste is reallocated to agriculture (Elser & Bennett, 2011). Common methods are chemical precipitation and biological phosphorus removal. Chemical precipitation involves adding coagulants, such as aluminium or iron, that bind to inorganic phosphorus. However, chemical precipitation leads to large sludge volumes, requires costly chemicals and reduces the biodegradability of the produced sludge through produced inorganic solids (Shu et al., 2006). Furthermore, chemical phosphate removal could produce metal phosphates (e.g. FePO4) which are unusable as fertilizers (Wilsenach et al., 2007).
Biological removal uses bacteria that incorporate phosphorus into their cell biomass. Treatment plants that possess a biological nutrient removal system (BNR) and a digester could solve these issues through (controlled) struvite crystallization. The concept of BNR and digestion is fairly complicated: under aerobic conditions, bacteria take up phosphate in excess of their nutrient
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requirement (luxury phosphorus) by building polyphosphates (Waternet, 2015). The hydrolysis of these polyphosphates in anaerobic conditions result in the release of orthophosphate, ammonium and CO2 - which increases the pH-level. Above pH-levels of 8.0, the increasing phosphate concentration leads to supersaturation (Wilsenach et al., 2007). As soon as the molar ratio of Mg:N:P exceeds 1:1:1 the solution precipitates with the added magnesium: Mg2+ + NH4+ + PO43- + 6 H2O -> MgNH4PO4.6 H2O (Veltman, personal communication, 2015).
In terms of recovery rates, up to 97% of the dissolved phosphorus content can be removed if the pH level is 9.0 since this results in the minimal solubility of struvite. However, if molar ratios decline, the removal efficiency decreases and a mixture of struvite and hydroxyapatite could appear. In order to achieve the highest efficiency, a magnesium dose of 1.3:1 is recommended (Jaffer et al., 2002). Hence, the process requires a continuous input of magnesium. According to Shu et al. (2006), 50-80% of the total phosphorus in wastewater can be recovered through struvite crystallization.
1.1.3 CENTRAL VS DECENTRAL RECOVERY
All of these processes happen at central treatment plants, where the incoming wastewater is a diluted mixture of urine, faeces and other materials such as cellulose. The result is a large amount of wastewater, which has to be transported, treated and incinerated. This is highly inefficient as urine contains 25%-67% of the phosphate content in wastewater, while it accounts for just 1% of the total volume (Wilsenach et al., 2007). The huge range of this figure is because of the different diets between developed/developing countries. For instance, Swedish diets have 67% of the excreted P in urine, while average Chinese diets contain a mere 40% (Mihelcic et al., 2011). In addition, treating urine is more efficient because the phosphorus is already dissolved and thus recovery rates are higher (Shu et al., 2006).
No-mix toilets and waterless urinals could collect urine separately, which increases the capacity and effluent quality of WWTP’s (Elser & Bennett, 2011). However, the current sewage infrastructure is not adapted to no-mix toilets.
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Replacing the complete sewage system would be economically infeasible. Decentral treatment at households, neighbourhoods or communal buildings could be an option. The struvite would be produced locally, while the treated liquid would be discharged via the existing sewage system. The required bed reactors are however rather complicated and economically inviable at smaller scales (Wilsenach et al., 2007). The efficient recovery of phosphorus through decentral urine separation does not yet outlift the high maintenance costs of reactors and the low struvite prices (Veltman, personal communication, 2015). An exploration of how this can be improved will be discussed in chapter 3.
Because of these reasons, it is considered that nowadays central treatment of urine at WWTP’s can make a more significant contribution to phosphorus recovery. Nevertheless, emerging neighbourhoods and cities could be equipped with a no-mix sewage system. Eventually, this is useful if decentral treatment becomes economically viable.
1.2. RECOVERY AND FERTILIZATION POTENTIAL OF STRUVITE 1.2.1 PROPERTIES OF STRUVITE
Many experiments have been done in order to assess the effectiveness of struvite compared to commercial fertilizer. According to the available literature, struvite is a good quality fertilizer. Gonzalez Ponce et al. (2007) compared the effectiveness of struvite in contrast to insoluble phosphate rock and two other conventional soluble phosphate fertilizers on ryegrass. They concluded that struvite is at least as effective and in some cases even more effective than the other sources. Struvite has several advantageous properties that account for this effectiveness.
First of all, struvite is a so called slow-release fertilizer (Shu et al., 2005; Latifian et al., 2012; Rahman et al., 2013), meaning that its nutrients are released into the soil at low rates. Therefore, it has a long residual effect at plant root zones, making the uptake of nutrients more efficient (Rahman et al., 2013). Its slow release rate also highly reduces nutrient loss through leaching, making struvite a more eco-friendly option than commercial fertilizers (Rahman et al.,
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2013). This property makes struvite highly preferable at coastal zones, as it reduces the risk of eutrophication of nearby waters (Shu et al., 2005).
Due to its low solubility in neutral conditions, struvite does not burn roots when over-applied (Shu et al., 2005; Rahman et al., 2013). As the crystals dissolve, they slightly increase soil pH levels. Hence, struvite works well on acidic soils. Additionally, due to its low specific gravity, struvite is not easily washed out by rainfall. Struvite can thus be successfully applied in areas that face frequent floods (Rahman et al., 2013).
Initially, concerns existed about the amounts of toxic substances and heavy metals that would be present in the crystals obtained from waste water (Uysal et al., 2007; Latifian et al., 2012). Several studies have now shown that heavy metal contents for struvites are safely below legal standards (Uysal et al., 2007; Latifian et al., 2012). In fact, Latifian et al. (2012) were able to prove that struvite contain less heavy metals than commercial fertilizers. However, it should be noted that heavy metal contents are determined by the conditions at which struvite is formed, and should always be monitored. In addition, Uysal et al. (2007) showed that struvite does not contain toxins such as PCB’s.
Finally, although struvite is often referred to as a phosphorus source, the crystals contain significant amounts of nitrogen and magnesium as well (Rahman et al., 2013). These too are vital elements for plant growth.
1.2.2 COST EFFICIENCY
According to Shu et al., the average concentration of phosphorus in wastewater is 4mg/litre. This would mean that there should be a recovery rate of 96,78% in order to recover 1 kg P from 100m3 wastewater per day (Shu et al., 2006).
While generating a valuable product, controlled struvite crystallization also reduces cleaning costs as it prevents struvite formation in pipelines (Veltman, personal communication, 2015). Savings on chemicals and sludge handling could therefore, be an effective incentive for WWTP’s to accumulate struvite. An economic valuation of this is as follows (WWTP of 100m3 per day) (see table 2): Revenues for struvite are up to $0,74 per day. It is estimated that the cleaning and downtime costs are AUD $16,45 per day. The estimated
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chemical costs are AUD $0,27 per day with a sludge volume of 3.5 litre. The struvite sludge has a volume of 0.7 litre, resulting in a saving of AUD $1.133 per day (Shu et al., 2006). With these figure, the savings of a WWTP that treats 55.000 m3 wastewater per day is AUD $436.211,5 per year. A struvite plant costs on average 2 million dollars, which would be paid off in 4,6 years according to this scenario (Veltman, personal communication, 2015).
It can be concluded that struvite is a highly effective, eco-friendly and sustainable fertilizer. 1 kg of struvite would be enough to fertilize 2.6 ha of arable land when the desirable fertilizing rate is 40kg/ha/year (Rahman et al., 2013).
Costs 100 m3/d 100 m3/year 55000 m3/year
Struvite gains $0,74 $270,1 $148.555
Reduction chemicals $0,27 $98,55 $54.202,50
Reduction sludge handling $1,133 $413,55 $227.449,75
Reductions cleaning and downtime $16,45 $6.004,25 $6.004,25
Total $18,59 $6.786,45 $436.211,5
Table 2: Costs reductions and gains for struvite recovery (Shu et al., 2006).
1.3 SUFFICIENCY OF STRUVITE FERTILIZERS
To what extent could the Netherlands produce enough phosphorus from wastewater or separated urine to meet its fertilizer demand?
Through fertilizers, imported feed/food and imported feed additives, large amounts of non-renewable phosphorus flows into the Netherlands. Smit et al. (2015) have analyzed the entire phosphorus flow of the Netherlands. The major phosphorus systems that exist in the Netherlands are agriculture, industry, household/retail, waste, surface water and lost phosphorus (e.g. incineration or cement processing).
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Figure 2 illustrates the subsystem agriculture. The thickness of the flows resemble the relative share and where applicable the accumulation of phosphorus is mentioned in the rectangles (e.g. arable land has an annual accumulation of 6,3 Mkg). Flows that possess of an E or I refer to export and import. As can be observed, the primary P inflow is imported or produced feed (F8) and fertilizer (F4). The main outflow are agricultural products to the industry (F13). The difference between these two flows (11,8 Mkg) is the accumulation of P in the soils.
Figure 2: P flows in the agricultural subsystem in 2011 (Mkg P/a) (Smit et al., 2015).
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Figure 3: Percentual share of the phosphorus inflows in the Netherlands in 2011.
The subsystem industry is observable in figure 4. Its largest inflow is imported feed and food, feed additives and domestically agricultural products. Since we are interested in household waste, the ‘Food, Detergents’' flow (F15) is relevant. This contains 20,6 Mkg of P, which is much more than the fertilizer demand of the Netherlands (7,0 Mkg). However, it should be noted that this P flow is not entirely consumed, as a significant proportion is lost prior to consumption (e.g. food waste).
Figure 4: P flows in the industrial subsystem in 2011 (Mkg P/a) (Smit et al., 2015).
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Of the entire ‘Household to Waste’ flow, 10,8 Mkg (F42) is turned into sludge that currently ends up incinerated (Smit et al., 2015). The other 7.5 Mkg (F52) is lost through food waste and such. In order to meet the dutch direct fertilizer demand (which is 7.0 Mkg), at least 64% of the present phosphorus should be accumulated. This is possible because according to Shu et al. (2006), 50-80% of the total phosphorus in wastewater can be recovered through struvite crystallization (this range is due to the maintained circumstances such as pH-levels and magnesium dosing). While Amsterdam’s Waternet currently only accumulates 20% of the present phosphorus in Amsterdam’s wastewater, other dutch companies such as Ecophos are beginning to capture the remaining 80% (Alex Veltman, personal communication, 2015). The difference between these figures is because Waternet only recovers dissolved phosphorus, while Ecophos also treats the phosphorus in wastewater sludge and ashes. Waternet could gain higher rates if circumstances improve such as pH-levels or magnesium dosing. A further analysis about the lack of incentives to do this will follow in chapter 3 about societal change.
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Figure 6: Percentual share of the phosphorus flows in the wastewater system in 2011.
Although a total of 23,2 Mkg of phosphorus can be recycled if appropriate technologies are available, domestic recycling is not essential considering the relatively small amount of phosphorus fertilizer application. However, future scarcity could impose problems, and despite these figures, the Netherlands actually has a major phosphorus deficit as it imports 110.5 Mkg of phosphorus through food and feed. In opposite, only 69 Mkg is exported in terms of food, nonfood and manure, resulting in a negative balance of 41,6 Mkg in the entire process (Smit et al., 2015). This balance could be levelled if waste flows (23,2 Mkg), leaching/runoff (6,6 Mkg) and soil accumulation (11,8 Mkg) are minimized.
While the current system and its phosphorus flows have been determined, a closer look will be taken at recovery through separated urine treatment. As it has already been mentioned, it is economically infeasible to replace the current sewage system with a no-mix sewage system. For that reason, we will look at new neighbourhoods, buildings and cities where new sewage systems can be constructed.
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The expected construction requirement from 2015 until 2030 are 647.530 households (Primos, 2013). Each person excretes an average of 1.2 grams of phosphorus per day and the average household in the Netherlands consists of 2,2 persons (Elser & Bennett, 2011; CBS, 2013). These figures combined make up a phosphorus waste flow of 0,62 Mkg per year. 67% of this phosphorus is present in urine and through separation (with a recovery rate of 97%) a quite significant 5,79% of the dutch fertilizer demand is covered. Nevertheless, new households can not be linked to the common sewage systems. In order to establish an undiluted urine flow, there should be a new main sewage line that connects the new households to central treatment plants. However, this still does not boost the efficiency, since the central WWTP’s would treat the wastewater as a diluted mix (unless intervals would be installed that transit between diluted and undiluted wastewater). In order to effectively benefit from urine separation, this urine should be treated at a decentral-level (Wilsenach et al., 2007).
In conclusion, the current direct fertilizer demand can be met through struvite crystallization at central WWTP’s, with a surplus if recovery rates exceed 67%. Consequently, short term export of recovered phosphorus becomes an option, which is a feasible option in the case of struvite. Unfortunately, the Netherlands have a real negative balance in phosphorus because of the major imports. Because of this, it is considered thoughtful to retain phosphorus in the Dutch system, because of geopolitical risks that will be further explained in chapter 3.
Future decentral treatment of separated urine could potentially improve recovery rates of phosphorus at lower costs, which stimulates the transition towards a human phosphorus cycle in the Netherlands.
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CHAPTER 2: THE DUTCH PRACTICE
2.1 THE BUSINESS POTENTIAL OF STRUVITE FERTILIZERS 2.1.1 THE MARKET AS GOVERNING SOURCE
Phosphate rock is one of the most highly traded commodities on the international market (Cordell & White, 2007). Since phosphorus is a non-renewable resource, it is expected to increase in value. At this moment, the full economic benefits of conserving resources are not being recognised because we fail to bring to account the full cycle of savings (Münch et al., n.d.). An institutional analysis by Kerschner and Cordell (2007) about the dominant institutions and actors governing phosphorus reveals there is no single international organisation or regime responsible for long-term management of global phosphorus resources for food production. In the absence of any deliberate international oversight, the forces of the international market and national interest govern phosphorus resources (Kerschner & Cordell, 2007). As described in the theoretical framework, this market is not sufficient to keep up with the rate of change of the global biophysical phosphorus cycle, as it does not recognize our planetary limits to growth. Furthermore, since phosphate rock is, geologically, concentrated in a few countries (Marocco, China and the US), only these nations are entitled to exploit the resources within their political boundaries (Cordell, 2008).
Economic solutions that reduce phosphorus loss and improve use-efficiency need to be found that seek to incorporate supply- and demand measures worldwide (see figure 8). A global adjustment could be the creation of phosphorus-emission markets, similar to carbon markets (Smit et al., 2015). Furthermore, the supply risk of phosphorus is not only related to the political-economic stability and production level of producing countries, but also to the potential of substitution and recycling rate (Scholz & Wellmer, 2011). Therefore, a Chain Agreement Phosphate cycle has been signed in October 2011, with the aim to establish an European market for recycled phosphate. This agreement was the first step towards the application of
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scale installations that can recycle phosphorus from wastewater to struvite (Ketenakkoord fosfaatkringloop 2011; Lesschen et al., 2013).
Figure 7: Meeting future global phosphorus demand through a range of ambitious demand and supply-side measures (Mitchell et al., 2015)
2.1.2 BUSINESS BEHIND PHOSPHORUS RECYCLING
Sourcing phosphorus from more localized places, rather than depending on access to a scarce global commodity, exposes potential for the exploitation of recovery possibilities and niche-innovations for businesses (Cordell & White, 2011; Dery & Anderson, 2007; Gilbert, 2009). In this business environment, competitive advantage can be obtained by cost advantage (Grant, 2010). The potential cost efficiency of struvite production at WWTP’s is explained earlier under sub-question 2. Other key goals for the WWTP is identifying spatial distribution between nutrient recovery systems and end users (key potential customers), determine fertilizer market characteristics, customer requirements (e.g. farmer’s preferences) and the size of the market (Munch et al., n.d.).
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However, an important barrier in the production of struvite is the tension between public and private interest. Public interest is a precondition for successful resource management (Ostrom, 1990). Nevertheless, the production of struvite is for a large part driven by private interest. This tension is perfectly illustrated in the case of Waternet. Waternet is a state-owned company, founded by the municipality of Amsterdam and the waterboards of region Amstel, Gooi and Vecht (Veltman, personal communication, 2015). Waternet is a public organisation and commissioned by the city council and water boards. Although Waternet can be considered as a business, legal constructions were required to be able to sell struvite. In 1995 the Reststoffenunie was founded by Dutch water conservancies, as a second party that legally sells rest products to buyers and brings the profits back to Waternet (Veltman, personnel communication, 2015).
Currently, the economic incentives for struvite production are low because the selling price of rock phosphate is lower than the price of phosphorus recovered from sewage, which implies sale difficulties of struvite (figure 8) (Molinos-Senante, Hernández-Sancho, Sala-Garrido, & Garrido-Baserba, 2011). The price of struvite, despite higher than phosphate rock, is also remarkably low since it is correctly and entirely valued, shown in figure 8 (Etter, Tilley, Khadka & Udert, 2011). These low prices are a shame since the environmental and internal benefits are high but not calculated directly in the price of struvite and therefore only defined by the fertilizer market (Molinos-Senante et al., 2011). Internal benefits include reduced operating costs of WWTP’s. External benefits are an increase in the availability of a non-renewable resource and environmental benefits. In an undistorted free market, the price determines the supply/demand (reserves/consumption) ratio of phosphorus. In the Netherlands, currently the price is demand driven, which decreases the price since improved nutrient efficiency and higher P-reserves. From the producer perspective, the selling price of struvite needs to rise, which will only happen when the recognition of its value will increase and by integrating external benefits and increasing phosphate shortage. However, from a farmer’s perspective, prices should not rise further, as they benefit from low selling prices. Thus an equilibrium must be found.
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amount price
Recovery cost Phosphate Rock 84 g
RP/d
0.0020 Euro/g P
Sold Phosphate Rock 11 g
RP/d
0.00035 – 0.0005 Euro/g
Sold struvite by Waternet 3 g P/d 0.00080 Euro/g
Sold struvite as normal fertilizer 9 g P/d 0.00220 Euro/g
Sold struvite as boutique fertilizer in Japan
9 g P/d 0.03491 Euro/g
Table 8. Different cost of struvite and its recovery compared to Phosphate rock (Molinos-Senante, Hernández-Sancho, Sala-Garrido, & Garrido-Baserba, 2011; Veltman, 2015)
As mentioned earlier, also no-mix sanitation systems in new neighbourhoods in the Netherlands can produce struvite. A volatility calculation is carried out by Desah for the project Nieuw Sanitatie Noorderhoek in Sneek. Data shows that the costs greatly depend on the size of the system. Currently, 35% of the phosphorus conveyed in Noorderhoek is recovered as struvite, which is already a higher percentage than Waternets recovery rate (Stowa, 2014). Unfortunately, until now, nothing is done with the struvite. This is due to the relative low total amount of struvite produced (small scale), plus low fertilizer prices and sales restrictions (Desah, personnel communication, 2015). Therefore, these initiatives are an exception to the rule and are generally not operating within a broad scale coordinated framework linked specifically to domestic sustainable nutrient recovery (Mitchell et al., 2015).
A real struvite market in the Netherlands can only be shaped when all water conservancies in the Netherlands will operate like Waternet, so that the amount of struvite becomes large enough to supply the Netherlands in total (Veltman, personnel communication, 2015). Clearly, there is economy of scale
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that proves the affordability of the technique (Porter, 2008; Cordell, 2006). Waternet has the ambition to make much higher profits, is still dependent on low selling prices of struvite, which are not expected to rapidly change. Properly framing markets may be seen as a governmental challenge, since opportunities and threats are principally related to legislation, whereof an explanation will be outlined below (Veltman, personnel communication, 2015; Scholz & Wellmer, 2011).
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CHAPTER 3: SOCIETAL CHANGE
3.1 A POLITICAL TRANSITION
Subquestion 1 explored the technical possibilities of different practices of recycling phosphorus from urine, regarding yields and efficiency. Subquestion 2.1 investigated the current struvite market, current business incentives for working with struvite fertilizers and barriers for new businesses to emerge. This section will explore what would be the best strategy to overcome these barriers. How can the mismatch between what is technically possible (subquestion 1) and what is now happening in practice (subquestion 2.1) be overcome? We will do so using the Multi-Level Perspective (MLP) on transitions, that was earlier appointed in the theoretical framework (Geels, 2002). The method involves an analysis of the current context of phosphorus recycling in the Netherlands, and in particular the potential for further change, based on the MLP. The basic idea is that the best way to develop a strategy is to include not only the interests of different stake-holders and a so-called “public interest” (which is inherently disputable), but also the power of social structures such as routines, relationships and cultural values. What are the most appropriate forms of transition management for the different trajectories of change as outlined by transition theory? What kinds of tools, instruments and means can guide niche and mainstream actors towards a transition pathway in ways that suit them best?
3.1.1 THE MULTI-LEVEL PERSPECTIVE: FOCUS ON SYMBIOSIS AND TIMING The basic premise of the MLP is that transitions in existing regimes are sometimes difficult to establish because the existing socio-technical systems are stabilized in many ways (Amstel et al., 2012). Unless innovations fit into the existing socio-technical trajectories, there tends to emerge a robust resistance to (radical) change. This is why the focus of our analysis will be on the symbiotic potential between actors and practices, or on the contrary, competitive relationships (Geels, 2011). Furthermore, the timing of the interactions between landscape, niche and regime is important. Particularly important is the timing of landscape pressure on regimes with regard to the state of niche-developments. If landscape pressure occurs at a time when niche-innovations are not yet fully
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developed, the transition path will be different than when they are fully developed (Geels, 2007).
According to the descriptions under the previous subquestions, the landscape pressures and different actors and practices that are involved in phosphorus recovery, can be identified. Furthermore, the suited nature of multi-level interactions can be determined: symbiotic or competitive? A symbiotic relationship or potential relationship is based on mutual benefits, while competing niche-innovators intend to replace regime practices and actors. By doing so, this paragraph will result in suggestions for a practical strategy in fighting phosphorus depletion, as well as it is a scientific contribution to the operationalization of the MLP for case studies, which is a developing field (Geels, 2002; 2007; Kemp, 2007; Amstel et al., 2012).
3.1.2 THE MULTI-LEVEL PERSPECTIVE ON PHOSPHORUS USE
In figure 9, an overview of the analysis of phosphorus use can be found.
Landscape pressures
In the case of P depletion, important overarching developments at the landscape level are sustainability and globalization. Both are identified by Spaargaren et al. (2012) as the two most influences on today's agricultural and food practices. Sustainability landscape pressures specifically involve the physical notion that phosphate mines can eventually be depleted and are irreplaceable (Cordell & White, 2011). Globalization landscape pressures specifically involve geo-political risks and uncertainties. As stated in subquestion 2.1, phosphate rock is, geologically, only concentrated in a few countries. Only these nations are entitled to exploit the resources within their political boundaries and make others dependent. The risk of dependency is that prices of food can rise high.
However, because of the large time-scale of these scenario, the pressures are not only physical, but also ideological. As explained in the theoretical framework, research about urine or wastewater recycling is rooted in the school of thought that views waste as a valuable resource: circular economy. It is the conviction that society should manage risks like phosphorus depletion in a
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sustainable way, that exerts an important pressure on the structured regime as well (Ehrenfeld, 2000; Despeisse et al., 2012).
The geo-political landscape pressure is also based on the conviction that
the risks that are accompanied with geo-political dependency, should be limited.
From the MLP, the timing of the rise landscape pressures will be crucial in how the transition will develop. As stated in the theoretical framework, there is an ongoing debate on when a phosphorus-peak will occur (Wouters & Bol, 2009; Edixhoven et al., 2014). If peak phosphorus occurs, this will put greater stress on the regime, which creates more opportunities for niche-innovators to become established.
Figure 9: The Multi-Level Perspective on Dutch phosphorus recovery. Grey boxes represent actors, white boxes represent routines and practices.
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The current socio-technological regime and niche-innovators
As explained in section 1 different techniques of struvite fertilization are possible. Because of multiple technical complications with chemical precipitation, biological precipitation became more developed and is now applied inside different WWTP’s across Europe (Veltman, personal communication, 2015). The crucial point here is that the biological precipitation of struvite from wastewater has a high symbiotic potential with sophisticated WWTPs and sewage systems: controlled struvite crystallization reduces cleaning costs as it prevents struvite formation in pipelines (Veltman, personal communication, 2015).
Furthermore, niche-innovations for separating urine are competing with the current sewage system. As stated in section 2, the efficiency and costs of struvite precipitation can be greatly improved if urine is source separated through no-mix toilets. However, it is economically infeasible to install new pipelines for each building. Therefore, the symbiotic potential of this niche-innovation lies in the application in new-built neighbourhoods. The struvite would be produced locally, while the treated liquid would be discharged via the existing sewage system.
The no-mix technology is far less developed than struvite production from wastewater, whereas the latter is applied on a broader scale. The further development of niche-innovations like no-mix sewage systems will require Strategic Niche Management (SNM). SNM is the approach developed within the school of transition theory which comprises protecting niche innovations as important ‘seeds of transitions’ against destructive regulation and market competition for a limited period of time. The efficient recovery of phosphorus through decentral urine separation is currently susceptible to market competition because the investments do not yet outlift the high maintenance costs of reactors and the low struvite prices (Veltman, personal communication, 2015). Thus, technological improvements and greater economic incentives are needed in order to implement decentral treatment.
In the end, however, the broader social environment determines whether innovations will grow and develop (Amstel et al., 2012). For example, a
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relatively early timing of the phosphorus peak can enforce adoption of no-mix sewage systems to the current practice building new neighborhoods.
Additionally, struvite has a symbiotic potential for conventional agriculture, because of the good quality. Struvite is at least as effective and in some cases even more effective than the other fertilizers. Also, there is a symbiotic potential for organic agriculture, as struvite is considered a more eco-friendly option than commercial fertilizers. However, struvite is not well developed yet in price. The economic incentives for struvite production are low because the selling price of rock phosphate is lower than phosphorus recovered from sewage.
The production of struvite is conflicting with the current waste regulation policy. The most important constraints are worries about safety and quality of recycled struvite from urine. Despite the legal acknowledgement of struvite for agricultural uses in January 2015 (Rijksdienst voor ondernemend Nederland, 2015), Waternet has to repeatedly demonstrated the quality and safety of the product for legal purposes (Veltman, personal communication, 2015), while several studies have shown that heavy metal content is safely below legal standards. This is because there is no European end-of-waste regulation for struvite, individual countries have to use their competence to declare per case if the product is considered end-of-waste. Further EU-regulation would smoothen this process (de Jong, personal communication, 2015). Additionally, the market for struvite becomes really interesting if struvite would get a legal end-of-waste status on EU-level.
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CONCLUSIONS & RECOMMENDATIONS
In order to clearly apprehend the results and conclusions, the findings and recommendations will be summarized per chapter. The application of these conclusions will produce an interdisciplinary strategy that could tackle phosphorus depletion through struvite fertilizers.
Technical possibilities for struvite fertilization
It has become clear that the most favorable option for phosphorus recycling through wastewater is struvite crystallization. This process could take place at central WWTP’s that possess of a biological nutrient removal system and a digester. Decentral treatment and local urine separation could also be an option as this improves the efficiency of the recovery process. However, this exposes problems with transportation because the current (unreplaceable) sewage system mixes the wastewater.
The advantages of struvite in terms of recovery and fertilization are rather significant. Dissolved phosphorus recovery rates of up to 97% can be achieved. The controlled precipitation of struvite also reduces cleaning costs at WWTP’s and results in savings on chemicals and sludge handling. Furthermore, struvite is highly applicable as a fertilizer because it releases nutrients at low rates (low solubility), which is advantageous in coastal or humid areas. In addition, studies have shown that struvite does not contain toxins and heavy metals.
The situation for the Netherlands is quite positive. If 67% of the wastewater sludge is recovered (10,8 Mkg), the dutch fertilizer demand can be met. However, because of the major import of phosphorus through imported food and feed, the Netherlands are still vulnerable for global shocks and scarcities. For this reason, phosphorus import should be reduced, while losses should be minimized in agricultural-, waste- and surface water systems (nowadays 11,8 Mkg soil accumulation; 7,5 Mkg food waste and 6,6 Mkg runoff/WWTP-effluent). Decentral treatment at new households/neighbourhoods could boost the efficiency of recovery if separated urine is apprehended. This phosphorus waste flow could meet 5,79% of the fertilizer demand, which is rather significant.
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The Dutch practice of struvite production
Currently the economic incentives for struvite production are low because the selling price of phosphorus recovered from sewage is very low. These low prices are piteous since the environmental and internal benefits are high, while not calculated directly in the price of struvite because they are regulated by the market. Furthermore, low prices can be attributed to the competition with current fertilizers, and therefore with phosphate rock, which are even lower. In small scale projects, these low fertilizer prices, sales restrictions and a low struvite production volume are profit barriers. Thus, for the aim of the producer the price needs to rise, while from a farmer’s perspective, prices should not increase, as they benefit from low prices. Thus an market struvite price equilibrium must be found.
A real struvite market in the Netherlands can only be shaped when all water conservancies in the Netherlands will operate like Waternet, so that the amount of struvite Clearly, there is economy of scale that proves the affordability of the technique (Porter, 2008; Cordell, 2006). However, properly framing markets may be seen as a governmental challenge, since opportunities and threats are principally related to legislation.
Societal change: towards a strategy
A large part of the symbiotic potential between niche-innovations and regime is already exploited. Nutriëntplatform is a network organization that initiated and brought together all actors of the Ketenakkoord fosfaatkringloop (2011). They are cooperating to establish a sustainable market for struvite (Ketenakkoord fosfaatkringloop, 2011). The most important aim is to establish the end-of-waste status of struvite on EU-level, however; this network of actors has much more symbiotic possibilities such as the optimization of phosphorus recovery rates during the production of struvite and creating more public awareness about phosphorus depletion (perhaps with help from NGO’s). Therefore this network should become institutionalized as a lobby group and knowledge platform.
Nevertheless, further EU legislation is important for establishing a EU market for struvite, that can become global in the future.
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Also Waternet plays a key-role in connecting different actors, since this is the most important operating struvite producer of the Netherlands. The high symbiotic potential for the production of struvite in WWTPs should be further exploited, placing struvite reactors in other large WWTPs in the Netherlands.
However, Waternet could gain higher rates (50-80% instead of 20%) if circumstances in the reactor improve such as pH-levels or magnesium dosing, but the incentive lacks. This is because Waternet is momentarily focussed on cleaning costs reductions instead of optimizing sustainable struvite production (Veltman, personal communication, 2015). This illustrates the point that business incentives are not enough to create sustainable recovery. Fortunately, Waternet is being instructed by the water boards and municipality, since it is a state-owned company. They have the power to stimulate the optimization of phosphorus recovery rates and can strategically use this.
Because of the relatively low landscape pressures, compared to the doomsday scenario of increasing food prices and food insecurity that can arise when P resources become critically low, combined with the high symbiotic potential and the high development of niche-innovations (namely struvite production), a gradual transition is most likely. If landscape pressures rise, a more radical transition to routinely placing no-mix toilets in new neighborhoods is likely to be enforced. However, in our opinion this radical transition is something that should be prevented. No-mix toilets can progressively be placed, with the thought in mind that local struvite production can be established the future. This is happening at Schoonbeek in Sneek, where no-mix toilets are placed, while struvite is not yet being produced (Elzinga, personal communication, 2015). The infrastructure that is built today, should meet the scientific and technological possibilities of today.
The less developed niche-innovators, that deal with struvite production from separated urine (for example the housing project Schoonbeek in Sneek), have not utilized the symbiotic potential yet. For this reason, SNM can protect the niches from regime stabilizing powers, for example by means of subsidies and more academic collaborations.
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DISCUSSION
Even though our research only deals with a minor part of the global issue, more detailed research is required in order to find practical solutions to found niche-innovators for no-mix systems and new-sanitation projects. Practical research and the implementation of new-found techniques should be facilitated by the government and market.
The data and figures used in our research are general indications and serve as mere indicators. So far, a great deal of research has already been done on struvite. However, research methods differ widely. In order to gain specific numbers, individual research should be done for each WWTP or sanitation installation. Also because wastewater compositions differ per demographic region.
The MLP transition theory gives important insights in the role of social structures in transition management. However, the theory is still not fully sufficient for application on practical case studies like phosphorus depletion in one single country. There seems to be a gap between theory and the complex practice of highly interdependent actors and routines.
Besides the used methods and theories, our research is mostly valid for Western countries with advanced wastewater systems, since our strategy is focussed on central treatment. Decentral treatment of source separated urine could be a viable option for developing countries, however; the phosphorus content in urine is lower in these countries, resulting in less efficiency. Despite differences in recovery potentials, also an imbalance in necessity exists. Developed countries’ soils have high phosphorus contents, while poor countries suffer from soil infertility. Thus, without regulation, the recycling of struvite could increase global inequality.
Because developed countries such as the Netherlands have highly saturated phosphorus soils (Schoumans, 2008). Demand for struvite fertilizers is therefore not necessarily high. It may therefore not be entirely correct to argue for a closed mineral cycle in the Netherlands. Nevertheless the aim of this article is to find methods to minimise the loss of valuable minerals. In reality we would not have to keep all phosphorus within our borders. The eventual target should
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be a global sustainable phosphorus cycle. In the near future, struvite has the potential to be an important commodity on international fertilizer markets.
Lastly, it should be mentioned that the recovery of phosphorus from urine will not lead to a decrease in phosphorus usage in general. A shift in the perception of mineral use and the recognition of the finite nature of mineral reserves is needed to accomplish this. The creation of phosphorus-emission markets, similar to carbon markets could be implemented as tools for global mitigation.
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