Closing the global nutrient loop (CLOOP)

Closing the global nutrient loop

Today, common mineral fertilizers are produced from fossil mineral sources which offer an increasingly deteriorating quality and purity. As mineral deposits are depleting and the beneficiation gets more difficult, alternative fertilizers must be developed. CLOOP will demonstrate that a symbiosis between organic farming principles, protection of aquatic bodies and high crop yields is possible.

Recycled fertilizers are using sewage, sewage sludge and sewage sludge ash as raw materials and reuse their nutrients. First tests indicate that recycled fertilizers have a comparable nutrient bioavailability as mineral fertilizers. However, these new products are still largely unknown to the market.

The aim of the project CLOOP (Closing the global nutrient loop), is to examine the properties and effects on plant growth of such fertilizers with chemical, mineralogical and ecological analyses, as well as through pot and field experiments. Based on the findings, "NextGen Fertilizers" will be developed, whose nutrient release is synchronized with the actual plant's requirements during the growth period, so that nutrient losses are minimized. By disseminating the project results among potential users and policy makers, the global application for such fertilizers will be promoted.

The NextGen Fertilizer concept

The green line shows the behavior of an ideal phosphorus fertilizer in synchrony with crop demand. The orange line represents conventional water-soluble fertilizer, highly available in the early crop season and declining in the later crop season. Light and dark blue lines are formulations of NextGen Fertilizers in development.

Whereas - industry standard - water soluble fertilizers release all nutrients at once (as soon as the fertilizer granule is broken down by contact with water), NextGen Fertilizers release nutrients in maximum synchrony with the nutrient uptake of crops. A fertilizer working in compliance with the pursued principles would release low nutrient amounts in the beginning and high amounts during the maximum biomass production (and nutrient uptake) in the crop's growth cycle.

Project partners

BAM - Federal Institute for Materials Research and Testing
KWB – Kompetenzzentrum Wasser Berlin
Uni Bonn - Rheinische Friedrich-Wilhelms-Universität Bonn
University of Queensland, Australia
Universidad de Sao Paulo, Brazil
Outotec GmbH & Co. KG

Responsibilities of the project partners

Outotec coordinates the project and provides recycled fertilizers which will be produced in a large-scale pilot plant. BAM will focus on the optimization of thermochemical treatment of sewage sludge ashes and the preparation of fertilizers. Furthermore, BAM will perform studies on phosphate availability and on the prediction of the fertilizing effect for the produced fertilizers. The operating parameters and material data determined in the project will be used for Life Cycle Analyses (LCA) performed by KWB. The Rheinische Friedrich-Wilhelms-Universität Bonn will perform and coordinate the pot and field experiments. By involving the University of Queensland and the Universidad de Sao Paulo, the produced fertilizers will be tested in subtropical and tropical regions where nutrient losses from erosion, leaching and phosphate fixation are more problematic than in Europe.

Outotec Project Coordinator

Dr. Tanja Schaaf
Outotec GmbH & Co. KG
Ludwig-Erhard-Strasse 21
61440 Oberursel
Tel. +49 6171 9693 166
tanja.schaaf@outotec.com

Environmental objectives

Demonstrating the potential of new, non-water soluble fertilizer types from secondary sources in terms of contribution to the global challenges for plant nutrition, marine biodiversity and phosphate stewardship, the project aims at:

Increasing the phosphorus use efficiency in comparison to conventional, water soluble fertilizers that have an upper bound use efficiency of 50% (i.e. only half the applied fertilizer is used by crops) and a lower bound use efficiency of only 5% in case of highly weathered, acidic soils. The global distribution of acidic soils is shown in figure 2).
Reducing phosphate losses to aquatic bodies, eutrophication and algae blooms.
This is especially important at the Great Barrier Reef where the critical state is demanding fast action and real solutions to the problem of nutrient losses but applies generally to all water bodies. Globally, the levels of reactive phosphorus in the biosphere are now 3-fold above natural background (and higher in many water bodies) which demands urgent action and real innovation.
Eliminating the contribution of free acids in fertilizers to the acidification of soils.
Reduce the demand for the critical raw material (CRM) rock phosphate – deemed critical to the EU due to its high economic importance associated with a high supply risk (EU directive 2014) by substituting rock phosphate with phosphate from secondary raw materials to produce fertilizer and thereby.
Reducing or almost eliminating the waste flows of conventional fertilizer processes.

Science objectives

Innovative analytical methods will be developed, tested and normalized to allow a lab based definition of “synchronous release” fertilizers. A promising method for determining plant available P is DGT (diffuse gradient in thin films). This is done by incubating P sources in a P deficient (sandy) soil and analyzing bioavailable P with the DGT-method. This method has recently been used for detecting bioavailable P in soil and several studies have shown a high correlation with plant P uptake [1] [2] [3]. The DGT method is based on phosphorus diffusion mimicking P uptake of plant roots.

In addition, it may prove to be more universal in testing different fertilizing products in the context of different crop/soil systems than conventional analytical methods where P solubility in neutral ammonium citrate (Pnac) has shown the highest correlations with values measured after pot tests. It is important to provide robust analytical tools for predicting the fertilizing value of a product if water solubility should be abandoned as a quality parameter – one of the project objectives that should be achieved in the long run.

Jahrestreffen der ProcessNet - Fachgruppe Extraktion & Rohstoffe

March 12-13, 2018
Frankfurt, Germany

IWA Sweden Seminar – Phosphorous recovery from wastewater

April 11, 2018
Malmö, Sweden

IFAT 2018 – Run4Life

May 17, 2018
Munich, Germany

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