Sustainable phosphate – more information coming soon!
In the ReFARM project, a novel concept for manure processing is demonstrated at a farm in Grijpskerk, the Netherlands. ReFARM combines mechanical separation, anaerobic digestion and biocrystallization. The anaerobic reactor is designed an operated such that a rich calcium phosphate fraction can be recovered from the bottom and an ammonium and potassium rich fraction from the top.
The project builds on research at Wetsus on anaerobic calcium phosphate biocrystallization. The project will complement the research in the Wetsus research theme Soil. ReFARM is part of EIT Climate-KIC.
European agriculture currently depends heavily on mineral fertilizers produced from imported ore and energy-intensive processes like Haber Bosch. At the same time, there are carbon, nitrogen and phosphate emission from manure applied on the land, related to local surplus. Wetsus and EIT-Climate KIC aim to mitigate this by enabling circularity in agriculture by upscaling a process in which biogas, minerals and stable organics are recovered from manure for reuse.
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ViviMag is an EIT RawMaterials funded upscaling project for an innovative magnetic separation technology to recover the iron-phosphate mineral vivianite from digested sewage sludge. During the project, the technology will be demonstrated in an industrial environment by realizing a pilot installation. By the end of the project, in 2020, the technology will be ready for market introduction.
ViviMag will develop and up-scale a magnetic separation process to recover the insoluble iron phosphate mineral vivianite from the Sewage Treatment Plants (STPs) that rely on chemical Phosphate removal. The separation process will be applied on sewage sludge after anaerobic digestion. Anaerobic digestion reduces the sludge volume and recovers energy in the form of biogas. During anaerobic digestion Fe(III) is reduced to Fe(II), which results in vivianite formation.
The separation relies on the paramagnetic character of the vivianite mineral (figure 1). In the first stage of the project, a SLon magnetic separator (figure 2 and 3) will be used to investigate the vivianite separation from digested sewage sludge.
Phosphorus (P) is a limited resource and our agriculture relies on a steady supply. Phosphate rock is mined and processed to produce phosphorus containing fertilizers, like PK-fertilizers. However, exploitable phosphate rock reserves are found in just a few countries. The EU itself has hardly any phosphate rock reserves and depends nearly entirely on the import of this crucial resource; in 2005 the primary P import of the EU-27 was 1.8 Mton. Phosphorus use has to become more sustainable and should include P-recycling from secondary sources (i.e. wastewater). This will not only prevent eutrophication of surface waters, but will also minimize costs for disposal of phosphorus rich wastes.
Phosphorus rich waste streams such as sewage have a high potential for P recovery. Phosphorus has to be eliminated from these wastewaters to prevent environmental damage, like harmful algae blooms. Annually, Europe’s Sewage Treatment Plants (STPs) remove approximately 370 kton P by immobilization in the sewage sludge. The direct use of the sludge as fertilizer is problematic due to its bulky volume, the fixed nutrient ratios and the low bioavailability of a nutrient like phosphate.
Therefore, there is an increasing interest to separate the phosphorus in concentrated form from the bulk sludge for subsequent reuse in the fertilizer industry. The majority of Europe’s STPs apply chemical precipitation with an iron-based coagulant to achieve sufficient phosphorus removal.