développement de procédés de recyclage du phosphore sous une forme valorisable en agriculture – PHOSPH'OR
PHOSPH'OR
Phosphorus recycling from agro-industrial effluents: from labscale to pre-industrial pilots.
AVOIDING FRESH WATER EUTROPHICATION AND SAVING LIMITED RESOURCES BY RECYCLING P AS MINERAL FERTILIZER
P is an essential component for life. P is provided to plants and animals as mineral form, resource whose<br />mining reserves are estimated between 100 and 250 years. P is badly assimilated and partly excreted in the<br />environment. An excess of P in surface water leads to eutrophication, degrading the biological status,<br />compromising fishing, fish farming or leisure and increasing the drinkable water production cost. We are facing<br />a paradoxical situation with an excess of P whose treatment is expensive, on one hand and the need for<br />importing phosphate-enriched fertilizers whose reserves are limited, on the other hand. The main sources of P<br />which can be recycled are livestock and agro-industrial effluents. This project made it possible to acquire<br />knowledge on the extraction and the crystallization of P from these effluents. This knowledge will be used to<br />develop two new processes. The phosphate-enriched fertilizers, containing struvite, produced from effluents is<br />as effective as phosphate-enriched fertilizers from mines, reducing the agricultural and industrial impacts on<br />ground and water while preserving the resource.<br />
The first process (P1) is designed for the effluents in which P is present mainly in particulate mineral form and
the other (P2) for the effluents whose P is mainly dissolved. In both cases, P is recycled as struvite and/or
calcium phosphate in a medium containing a high amount of organic matter. Batch tests were carried out to
confirm or implement knowledge on P crystallization in organic medium (influence of the process parameters,
ionic interactions, role of the organic matter). A Raman probe, innovating technical to following-up in situ
crystallization, was used to study the influence of various factors on crystallization and to determine the
thermodynamic constants and kinetics of the models.
The labscale pilots allowed to study the influent parameters and to design the preindustrial pilots tested on effluents, in situ. The P fertilizing value of the products from recycling processes was tested by pot tests with 32P. Data obtained made it possible the
economic and environmental studies aiming at comparing the innovating processes with references. At the end
of the project, a P2 process is in construction on an industrial scale. The P1 pilot is effective and the product,
composed mainly of struvite, is a good substitute of the chemical fertilizers but it appears not very competitive
on the economic point of view. So, new works are in going to improve it.
The national dynamic created around
P recycling by this project, made it possible to acquire an international visibility of the research teams implied.
That is concretized by the continuation of work on the P1 process within the framework of a European project
submitted in October 2014.
A patent was deposed on the process P2 by the LISBP and Valbio. The results,
describing the chemical and biological mechanisms and their models, were published in international scientific
journals. The pilots were presented to the professionals involved in effluent management during technical days
as the “Journées de la recherche porcine” or the “journées d’informations sur l’eau” and during two seminars,
intended for all the stakeholders concerned with the recycling of P, which were organized in Toulouse and
Rennes.
Project coordination
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
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Beginning and duration of the scientific project:
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