Phosphorus recycling: Facts and perspectives

Dr. Rainer Schnee, Deutsche Phosphor-Plattform e.V., Board of Directors

Phosphor gehört rein mengenmäßig zu den häufigsten Elementen der Erde. Er liegt aber nicht in elementarer Form vor, sondern fast ausschließlich in Form des Phosphat-Anions PO43- bzw. in mineralischen Phosphatsalzen. Die größten Phosphatmengen liegen in mineralischer Form in der Erdkruste, der Geosphäre vor. Ebenfalls große Mengen sind in den Gewässern und Meeren gelöst. Und ein weiterer Anteil findet sich in mannigfaltigen Funktionen in der Biomasse. In den terrestrischen Lebensprozessen spielt demnach Phosphat eine essentielle, lebensnotwendige Rolle.

Da keine nennenswerten Phosphatmengen über die Atmosphäre transportiert werden, ist die Mobilität im Boden und im Wasser entscheidend. Gegenwärtig werden pro Jahr über 200 Millionen Tonnen Phosphat aus mineralischen Lagerstätten gewonnen und vor allem in der Landwirtschaft als Dünger und Futtermittel eingesetzt. Insofern ist die lokale, regionale und globale Verfügbarkeit von Phosphat für die Futter- und Nahrungsmittelproduktion lebensentscheidend und nicht substituierbar. Zusätzlich werden Phosphor und Phosphate in der Nahrungsmittel-, Waschmittel-, Baustoff-, Halbleiterindustrie in verschiedenen Funktionen eingesetzt. Ein umfassendes und detailliertes Monitoring der gegenwärtigen und zukünftigen Phosphor-Stoffströme ist unabdingbar für das Verständnis und das Management seiner raum-zeitlichen Dimensionen und Funktionen.

Von zentraler Bedeutung wird die effiziente Nutzung als Düngemittel sein. Damit einher gehen eine Optimierung der Pflanzenverfügbarkeit, eine Minimierung der dissipativen Verluste, eine möglichst geringe Eutrophierung der Gewässer und eine möglichst hohe Rückgewinnung als Sekundärrohstoff mittels Akkumulation und Recycling in den technisch-industriellen und biologischen Wertschöpfungsketten. Das sind zusammen mit den sozio-ökonomischen Kontexten die Eckpfeiler einer zukunftsweisenden Ressourcenstrategie für Phosphor.

Als Grundlage für die Bewertung der Kritikalität von Phosphor wird ein Ressourcenstrategie-Konzept angewendet, das anhand spezifischer Kriterien den Lebenszyklus und seine unterschiedlichen Wertschöpfungsketten von der Förderung in den Lagerstätten über die Aufbereitung, Funktionalisierung und Nutzung in mannigfaltigen Prozessen und Produkten bis hin zur Nachnutzung oder Entsorgung erfasst, analysiert und bewertet. Eine Kritikalitätsanalyse für Phosphor ergibt u.a., dass

• nach menschlichem Ermessen zwar ausreichend Reserven vorhanden sind, aber nur wenige Lagerstätten den Weltmarkt beliefern und diese sich aus geographischer und geopolitischer Sicht teilweise in kritischen Regionen befinden.
• viele mineralische Phosphatquellen mit Schwermetallen und radioaktiven Elementen belastet sind, die in der Aufbereitung zu Produkten, insbesondere zu Düngemitteln, unbedingt abgetrennt werden müssen um deren unkontrollierte Dissipation zu verhindern.
• der unsachgemäße Einsatz in der Landwirtschaft zur Anreicherung in Böden und zur Eutrophierung von Gewässern führen kann.

Weitere technisch-funktionale, ökonomische, ökologische, soziale und politische Dimensionen der Phosphornutzung werden in Betracht gezogen und zu einer umfassenden Analyse und Bewertung seiner Kritikalität zusammengeführt.

P-ENG: Efficient phosphate recovery from agro waste streams by enzyme, strain, and process engineering

Prof. Dr. Lars M. Blank, RWTH Aachen University

The project focuses on the development of a new value chain to recover phosphate from plant waste material. The ultimate aim is to recycle phosphate into polyphosphates of new values. Therefore phytase, the enzyme able to release phosphate from plant material, is studied in this BioSC project. Through variations in protein modification (glycosylation) different properties such as thermostability or enzyme activity are optimized until a superior phytase is created. The impact of the enzyme production on the production host, the yeast Pichia pastoris, is analyzed with the whole metabolism in sight. Through this approach it is possible to predict steps in the cell metabolism during protein production which can be tuned to further improve phytase production. Bioprocess development contributes through establishing high-throughput screening environment in form of micro bioreactor systems. Utilizing that system clones generated by the other partners can easily be tested to identify the best producing strains. With the use of yeasts that collect phosphate it is possible to use the released phosphate to form polyphosphates. The possible market entries for superior phytase and polyphosphates are evaluated on a basis of market research, existing products, and company interviews. Furthermore the generic technology potential will be studied (e.g. IP).

Commercializing phosphorus from renewable resources: What are the major challenges?

Carolin Block, University of Bonn

The use of renewable resources opens up the way for more sustainable production systems. Recovering resources from low value by-products or waste streams reduces the dependency on fossil materials. However, the change from traditional to bio-based technologies leads to several challenges for value chain actors. Thus, actors for instance might face high switching costs, missing industry or quality standards. Moreover, in the bioeconomic setting actors from distinct industries need to establish new relationships leading to structural changes and emerging value chains.

In order to explore the challenges for the chain actors, a case study on a new technology for phosphorus recovery from rapeseed oil press cakes, a by-product in oil mills which ends up in animal feed, was carried out within the BioSC project P-ENG. The literature research and expert interviews with 4 different value chain actors (phosphorus processor, biotechnological company, rapeseed oil processor and feeding mix producer) reveal that there are challenges referring to five major categories, namely organizational, institutional and regulatory, economic viability, geographical and product quality issues. None of the current chain actors has the competencies to carry out the phosphorus recovery process from extraction to commercialization on its own. The results highlight the need for further research developments such as closer integration of academia and industry and economic viability studies to tackle these challenges.

PhytaPhos: Optimizing the phosphorus cycle in the sugar beet production process by phytase supplement

Anna Joëlle Ruff¹, Prof. M. Becker³, Dr. U. Arnold³, Dr. M. Trimborn³, Prof. U. Schurr⁴, Dr. S. Schrey⁴, A. Robles Aguilar⁴, Ulrich Schwaneberg^1,2

¹ RWTH Aachen University, Institute of Biotechnology, Aachen, Germany

² DWI –Leibniz Institut für Interaktive Materialien, Aachen, Germany

³University Bonn; Institute of Crop Science and Resource Conservation INRES, Bonn, Germany

⁴ FZ Jülich, IBG-2, Institute of Bio- and Geosciences: Plant Sciences, Jülich, Germany

Phosphate is a main component of fertilizers and therefore essential to feed humankind. Subsequently, recycling concepts for phosphorus are a key request to ensure a self-sustaining food production in Europe and to avoid rapid depletion of concentrated natural deposits. Within the BioSc-funded project PhytaPhoS, we propose a new value chain to recover phosphate from plant waste material. The principle storage form of phosphorus in plants is phytate (inositol hexaphosphate). The approach is based on the naturally occurring phytases that free the phosphate bound in an organic form. In sugar production processes this could be achieved by supplementing thermally resistant phytases to leach the phytate phosphate form sugar beet slices. With this procedure the phosphorus concentration in sugar beet slices in fodder and in consequence P-excess in fields will be reduced. Instead, isolated phosphorus will be transferred into spent lime and subsequently back to the sugar beet fields. Thereby a hub forward to an independent phosphorous use would be enabled and emerging value chains contribute to a sustainable bioeconomy.

Nutrient Removal with Microalgae –
Reduction of the Effluent Concentration from Wastewater Treatment Plants

 Wawilow, T.¹; Hasport, N. ¹, Theilen, U¹ and Thomsen C. ²

¹ THM - University of Applied Sciences - ZEuUS, 35390 Gießen, Germany

² Phytolutions GmbH, 28759 Bremen, Germany

An alternative, environmentally sustainable method to remove nutrients from wastewater is to integrate an algae-mediated wastewater treatment to reduce nutrient loads to preserve water bodies from eutrophication and generate effective biomass. Compared with conventional treatment methods the generated microalgae biomass is more energetic and rich in content with phosphorous (P) and nitrogen (N). Therefore, a tertiary biotreatment coupled with the production of potentially valuable biomass, which can be used for energetic or material purposes, is an efficient alternative to avoid using chemicals for the removal of phosphorus via precipitation and flocculation. Algae species Scenedesmus was applied for wastewater treatment and had proven abilities of removing nitrogen and phosphorous in retention time of 24 hours. In this study, a photobioreactor (PBR) was implemented for large-scale research to treat the effluent of the WWTP while microalgae growth rate, nutrition removal as well as operational and external conditions were evaluated. Moreover, the biomass was separated and methane potential tests were conducted using microalgae as substrate.

Detection and quantification of polyphosphates in microalgae by means of Raman microscopy

Peter Mojzeš, Institute of Physics, Faculty of Mathematics and Physics, Charles University, Prague, CZ

The potential of microalgae to sequester phosphorus from wastewater and to return it to agriculture as a fertilizer has emphasized the importance of microscopic methods allowing detection and quantification of polyphosphates in situ at single cell level. Confocal Raman microscopy, a method combining the molecular specificity of vibrational spectroscopy with spatial resolution of confocal optical microscopy, can be a method of choice, since Raman signal of polyphosphates is clearly recognizable even in the presence of other biomolecules in the same cellular region. However, routine applicability of Raman microscopy to microalgae has long been hindered by a strong autofluorescence of photosynthetic pigments. Recently, we have developed a simple methodology [1] for fast and efficient suppression of the algal fluorescence, which open the door to an unexplored world and enabled relatively rapid and simple quantification of polyphosphates from Raman chemical maps along with other biomolecules [2]. Recent progress in the field, advantages, limitations and pitfalls of the method will be demonstrated and discussed.

[1] Š. Moudříková et al., Algal Res. 16 (2016) 224-232.

[2] Š. Moudříková et al., Anal. Chem. 89 (2017) 12006-12013.

Luxury phosphorus uptake and diazotrophy in green algae & cyanobacteria: AlgalFertilizer and follow-up projects

Alexei Solovchenko*, Olga Karpova, Tatiana Ismagulova, Larisa Semenova, Irina Selyakh, Alexandr Lukyanov and Olga Gorelova.

Lomonosov Moscow State University, Moscow, Russia

*solovchenko@mail.bio.msu.ru

Sustainable usage of finite and non-renewable phosphorus (P) resources is a grave challenge to humanity. Shortage of P fertilizers threatens the food security. The P lost due in inefficient processing chain gives rise to eutrophication of water bodies. In view of this, potential environmental, social, and economic impact of currently non-sustainable usage of P is commensurate to that of oil and gas shortage.

Single celled phototrophs including cyanobacteria and eukaryotic microalgae featuring so called “luxury uptake” of P constitute promising vehicle for by sequestering the lost P and returning it, in form of P-rich biomass, to the field. The reasons are (i) fast growth rate of these organism, (ii) capability of rapidly taking up P up to 4­−7% of their cell dry weight, and (iii) gradual release of the accumulated P upon application of microalgal biomass to the soil in the from available to crop plants.

Diazotrophic species of cyanobacteria are capable of fixing atmospheric nitrogen (N). On one hand, this process makes them less dependent on the availability of N in the medium so cyanobacteria can potentially recover P from waste streams with imbalanced N:P ratio. On the other hand, diazotrophy is a very energy-intensive process which can compete for ATP with the processes of P acquisition and storage in the cell. The successful biotechnological application of cyanobacteria to close the P loop is limited by insufficient understanding of C/N balance impact on and the molecular mechanisms of luxury P uptake.

We report on the effect of diazotrophy on luxury P uptake and storage in the cell in a diazotroph strain Nostoc sp. PCC 7120 in comparison with a nearly-isogenic non-diazotroph strain Nostoc sp. PCC 7118. Although the P starvation and the fast phase of inorganic P (P_i) uptake were similar in both strains studied, induction of diazotrophy impared significantly the ability of PCC 7120 to accumulated inorganic polyphosphate (PolyP) in the cell. Since PolyP is a main P storage compound in the cell, the availability of N seems to of primary importance for efficient recovery of P from waste streams. Biotechnological implications of using diazotrophic and non-diazotrophic cyanobacterial strains for recovery of P from waste streams with different N/P balance are discussed.