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The European Nutrient Event, Basel, 18-19 October 2017, was organised by the European Sustainable Phosphorus Platform, FHNW School of Life Sciences, the Phos4You InterReg Nordwest Europa project, and the German Phosphorus Platform (DPP). The final report can be found on this page and in this PDF.

This meeting, Basel, 18th October 2017, was organised by FHNW School of Life Sciences, the Phos4You InterReg Nordwest Europa project, and the German Phosphorus Platform (DPP). 160 stakeholders were informed on the status of phosphorus recycling policy in Switzerland and Germany. The launch of the Swiss Phosphorus Network ( was announced.

The positions of Swiss sludge disposal operators were linked to a selection of possible phosphorus recycling technologies available and future developments discussed.

The day was moderated by Daniel Frank, German Phosphorus Platform (DPP).

Matthias Nabholz, Canton of Basel-Stadt, underlined that Germany and Switzerland are the first countries in the world to make phosphorus recovery obligatory, opening opportunities to become innovation leaders.

Phosphorus recovery regulatory obligations in Switzerland and Germany

Kaarina Schenk, Swiss Federal Environment Agency (BAFU), explained the new Swiss category of “Mineral Recycled Fertilisers” (see ESPP eNews n°15) which will accompany implementation of the federal phosphorus recovery obligation, introduced in the Waste Ordinance (see SCOPE Newsletter n°118). This fixes limits for heavy metals such that any accumulation in soils does not compromise safety for at least 500 years, whilst remaining technically feasible. NAC (neutral ammonium citrate) and 2% citric acid are considered better indicators of fertiliser value of phosphate than water solubility. The objective is that this new fertiliser category should be implemented from 1st January 2019.

At the same time, Switzerland is working to implement the Waste Ordinance phosphorus recovery obligation. This obliges recovery of phosphorus from sewage sludge or sludge incineration ash, and from slaughterhouse wastes. At present, the technical requirements of the phosphorus recovery obligation are not defined (e.g. what % of phosphorus must be recovered, where, under what conditions) and a technical working group will be launched in early 2018 bringing together the Kantons, industry and experts to make proposals. Nonetheless, BAFU underlined that current mono-incineration capacity (incineration of sewage sludge separately not mixed with municipal solid waste or industrial waste) is insufficient to take all Switzerland’s sewage sludge.

In discussion, participants at the meeting noted that until these criteria are fixed, it is premature to invest in phosphorus recovery in Switzerland, because technical choices made now may prove to be incompatible or too demanding compared to the final obligations. However, study of phosphorus flows and of logistics, and preparation of a move to separate mono-incineration should already be engaged.

Christian Kabbe, Isle Utilities, presented the status of the German phosphorus recovery legislation, which has been adopted at the same time as a revision of regulations concerning sewage sludge application to land. Although the regulations have now been adopted, implications of certain aspects remain to be clarified. To simplify, the new P-recovery legislation will require (within 12 or 15 years, for sewage works > 100 or 50 000 p.e.) recovery of phosphorus if P>2% DM in sludge. The same requirements apply to smaller WWTP if they cannot spread sludge on farmland. (around 24% of German sewage sludge currently goes to agriculture), but this is not clear in the final text. The sewage sludge use on farmland is acutely limited by the new fertilising regulation (German Nitrates directive) which limits the nutrient loads applied to land.

Anders Nättorp, FHNW, summarised phosphorus flows in Switzerland, He noted that phosphorus in sewage sludges is around 5 800 tP/y and in animal products around 1 500 tP/y in Switzerland, and that this is currently lost as sewage sludge goes to cement works. This phosphorus recovery potential is slightly higher than Switzerland’s annual consumption in mineral fertilisers. He summarised different possible routes for phosphorus recovery for which technologies are today available: precipitation from liquid streams; extraction or thermal treatment of sewage sludge; leaching, thermal treatment or acidulation of ash. Based on P-REX data (see SCOPE Newsletter n°115) he estimates that phosphorus recovery could cost 0 – 50 €/t of sludge in addition to current Swiss sludge disposal (incineration) costs of 90 – 140 €/t (tonne of dewatered sludge).

Waste and water companies’ positions

Alain Zaessinger, ProRheno (sewage works and sludge management structure) manage some 30 000 t/year of sewage sludge in North West Switzerland, together with ARA Rhein. They presented a study of investment options for replacing the ageing sludge incineration ovens in the two locations. The process is defined (mono-incineration) and will enable later phosphorus recovery, as required by the new Swiss legislation.

Christoph Egli, AVA Altenrhein (authority with c. 20 sewage works), underlined that we stand at the very beginning and for most Swiss WWTP it’s not clear which technology should be applied. Based on the lack of a robust technology readiness there should not be an overhasty exclusion of promising technologies at this point.

He points out the essential information which is needed concerning what the phosphorus recovery obligations will be under the new Swiss legislation: Where will this be required/whose duty is it? How much (%) of phosphorus must be recovered? What are the criteria for the recovered product: quality? phosphorus content? This means that it is impossible to decide what process to adopt, or to estimate costs.

The Swiss Water Association (VSA) will organise a workshop in January 2018 to identify the WWTP’s requirements. He furthermore presented sludge treatment in Altenrhein, costs of infrastructure and operation, underlining the role of the sludge treatment organisation KIGO in Eastern Switzerland. Furthermore he presented the Pyrophos (pyrolysis) project.

Claudio Bianculli, presented ZAB (Association for waste recycling Bazenheid), which provides sewage sludge treatment for a number of municipalities in East Switzerland (100 000 t sludge/year). Investment in modern incinerators enables cost-effective recovery of energy. Phosphorus recovery will be tomorrow’s challenge.

Phosphorus recovery processes

Stefan Schlumberger, ZAR, presented the Phos4Life process (see ESPP eNews n°12) being developed to recover phosphorus from 30 000 t/y of sewage sludge incineration ash from Kanton Zurich and other localities in Switzerland. This is currently being pilot tested in Spain. The ash will be dissolved in sulphuric acid, generating phosphoric acid and gypsum. This is similar to the wet acid process used by the phosphate industry to produce most of the world’s phosphoric acid. The gypsum, containing aluminium, silicon, calcium and sulphate, and c. 0.5% phosphorus (P), is expected to be compatible for use by the cement industry. The phosphoric acid will then be treated using solvent extraction and hydrochloric acid to remove iron, as iron chloride which can be recycled as coagulant P-removal salt to sewage works. The resulting phosphoric acid will then be purified using solvent extraction (process already used in the technical and food phosphate industries) to remove heavy metals and produce an industrial grade phosphoric acid.

The full scale Phos4Life P-recovery process is expected to cost 50-70 CHF/tonne of dewatered sludge, compared to current total costs of sludge treatment (digestion, dewatering, incineration) of c. 300 €/tonne (including costs for digestion, dewatering, transport and mono-incineration). These costs were about 400CHF (2014) before recent investments in the new centralized and more energy efficient incineration installation in the city of Zurich.

Patrick Herr, Remondis Aqua, presented the company’s TetraPhos® process (see SCOPE Newsletter n°123), which takes as input mono-incineration ash from fluidized bed combustion of municipal sewage sludge. The TetraPhos® process treats the ash with phosphoric acid, then, after separation of acid insoluble residue, purifies the resulting leachate with sulphuric acid, ion-exchange and selective nano-filtration to generate an industrial quality phosphoric acid. The process also enables recovery of iron and aluminium salts as coagulants, for recycling in sewage works phosphorus removal, gypsum intended for production of building material and a residual ash waste that either is used in the cement industry or if the latter is not possible is landfilled. More than 80% of the ash phosphorus is recovered in the phosphoric acid. Where designed as part of an integrated plant consisting of an incineration facility and a P-Recycling installation, waste heat can be used to concentrate the phosphoric acid product. The rollout of the technology will be implemented as public-private partnership between municipal partners and Remondis. From 2019, a large scale TetraPhos® plant at the Hamburg Wasser WWTP is planned to treat 20 000 tonnes of ash annually, to recover more than 1 600 tonnes of P.

Otto Schwarzmann, SUN Nürnberg (sewage works operator), presented experience of operating the Mephrec process pilot installation (0.6 t sewage sludge per hour capacity, batch operation). This process operates at >1400°C and generates a “slag” currently containing 2-2.5% phosphorus (P) and with low heavy metal levels. Operational difficulties encountered include: the quality of the syngas, generated by the recovery furnace, will not reach economically the standards of fuel-gas to use in electricity generation motors, because of high fly ash particle and coal tar content. Also, the fertiliser value of the slag remains to be proven (see SCOPE Newsletter n°115: P-REX results suggest low plant availability). This experience shows that developments and financial assumptions based on lab scale experiments have to be validated at a larger scale. At the moment SUN is negotiating with the project consortia about future collaboration.

Matthias Mann, Küttner GmbH, presented the Kubota furnace process. This is also a metallurgical approach technology with a furnace system operating on dried sewage sludge (80% dry matter) with a process temperature at >1300°C. Over 30 furnaces are operated by Kubota in Japan (see SCOPE Newsletter n°125), but not today for phosphorus recovery. Most of these are for sludge (mono or shared with household waste) disposal, producing a sage which can be used e.g. as a construction material. Studies are underway into possible phosphorus recovery in furnaces treating only sewage sludge as input. Around 90% of the input phosphorus is transferred to the thermal slag product (this slag represents around 92% of total input mass), whilst most of the contaminants come out in the flue gas from which they can be separated by standard flue gas treatment systems (8% mass). Results presented of pot trials (soil pH up to 7.2) show the slag giving similar plant harvests to triple super phosphate for rice, but c. 10% lower for wheat and grass.

Marie-Edith Ploteau, Lippeverband Germany, summarised four phosphorus recovery processes which will be demonstrated in the Phos4You Interreg NWE project (2016-2020):

  • Sludge bio-acidification (IRSTEA France) to solubilize phosphorus combined with  struvite precipitation (Struvia process from Veolia) at Lille WWTP (France). The combination of both reactors is expected to significantly increase the P recovery yield from sewage sludge liquor.
  • Chemical acid extraction of phosphorus from partially dried sewage sludge (Liège University) followed by a reactive-extraction step and fractionated precipitation to remove contaminants and finally a precipitation of calcium-magnesium phosphate that can directly be used as fertiliser ingredient. A mobile demonstration plant that will be used in by-pass at different WWTP throughout Europe will enable to adjust and validate the process in a corresponding simulation tool.
  • Thermochemical two-stage treatment of sewage sludge (EuPhoRe-process) including a reductive step at 650-750 °C and an oxidative one at 900-1000°C in a rotary kiln, as well as a flue gas cleaning. The process produces phosphate-rich ashes very low in contaminants in which phosphorus is expected to be plant available. A 100 kg dry matter input/hour pilot is to be built at Emschergenossenschaft´s installation in Dinslaken, Germany to validate the process and refine parameters. Parallel to Phos4You, the full-scale rotary sludge incinerator in Oftringen, Switzerland (30 000 tDM/y, manufactured in 1992), will be modified for large-scale implementation of the EuPhoRe process. This should enable the use of the ashes in the fertilizer production chain (instead of current disposal).
  • Acid extraction of phosphorus from sewage sludge incineration ash, followed by contaminant removal, will be tested at (pre)-industrial scale by the Lippeverband with different ashes from two incinerators of the Emscher-Lippe region, located in Bottrop and Lünen (DE).

Other Phos4You activities include studying sludge incineration ash quality from HVC Dortrecht (NL) and SNB Moerdijk (NL). The phosphorus recovery from these ashes is planned at the Ecophos full-scale factory in Dunkerque, France (see SCOPE Newsletter n°120

Fertiliser value and safety of the different recovered phosphorus products will be assessed. It was underlined that unrealistically high nutrient inputs (kgP/ha equivalent) as in some previous experiments should be avoided, and that soil pH is an important criterion (test in both slightly acidic and neutral soils).

Else Bünemann, FiBL (Research institute for organic agriculture) explained that around 2/3 of phosphorus input to agriculture in Switzerland currently comes from recycling of manure and agricultural byproducts. She presented experimental data on fertiliser value and solubility of recovered phosphate materials, using different extractants, mainly data from pot trials, including sewage sludge incineration ash (low plant availability), meat and bone meal ash (high in acidic soils), struvite (high). For some materials, plant availability and solubility depend on production process or characteristics: for example, one pyrolysis product showed low plant availability, but an alkaline pyrolysis product showed high plant availability. Availability of calcium phosphates depends on the crystal form. She concluded by underlining that water solubility is not a good indicator of plant availability, that plant availability depends strongly on soil pH, and can be modified by granulation/particle size.

Maurice Jutz, FHNW, announced the launch of the Swiss Phosphorus Network ( The network will facilitate exchange of information between Swiss actors considering also the different language regions and act as contact point to ESPP and other actors on the European level. Five demonstration projects in Switzerland are currently under way: Bern, Zofingen, Bazenheid, Zürich and Altenrhein.

Panel discussion and conclusions

Agency, Christoph Egli representing WWTP association Altenrhein and VSA (Swiss WWTP association), Cladio Bianculli, ZAB, mono-incineration operator and was moderated by Thomas Wintgens, School of Life Science, FHNW.

It was emphasised by the operators that today it is not clear what is required in terms of phosphorus recovery, nor how much it will cost. Because this is not fixed by regulation, it is not possible to pass the costs on to water consumers. The Swiss Federal Environment Agency replied that a study will be engaged in 2018 on conditions and cost, but that a new law would be necessary to allow to pass on costs. The Swiss Federal Office for Agriculture underlined that the price of recovered phosphate fertilisers must be the market price or farmers will not use them, and that recovered fertilisers must respect quality standards to ensure soil protection.

It was concluded that stakeholders can expect to be invited by Swiss regulators to work on the detail of implementation in early 2018. These should provide clarity whilst also enabling flexibility. The panel concluded by underlining the general support for the Swiss phosphorus recovery obligation, seen as offering important opportunities for improving sustainability and developing innovation, and the conviction that technologies under development will enable to achieve the objectives.

Ludwig Hermann, Outotec and President of the European Sustainable Phosphorus Platform (ESPP) closed the day and summarised conclusions:

  • The new German and Swiss phosphorus recovery obligations are already moving things forward, and will enable these countries to be innovation leaders
  • Work is needed to define implementation conditions and how costs can be passed on to consumers
  • A range of different technologies are under development, with different approaches and leading to different finished products
  • Agronomic performance of quality recycled phosphorus products is comparable to mineral fertilisers, despite their not being water soluble
  • Quality criteria are important to ensure safety for soil, crops and farmers, and confidence of users and consumers

Conference outcomes, slides and programme

Return to the SCOPE In Press section.

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