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ReUseWaste related PhD thesis on soil P-availability from manure products – University of Copenhagen

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4 July 2014

ReUseWaste related PhD thesis on soil P-availability from manure products

Wibke Christel, from Dept of Plant and Environmental Sciences at the University of Copenhagen, recently finalised her PhD thesis entitled: "Upgrading of the solid fraction of pig slurry as phosphorus fertilizer - The impact of biological and thermal processing on P availability".

Wibkes work is particularly relevant to work being done in ReUseWaste. Below is the summary of her work. Please write to Wibke Christel or Lars Stoumann Jensen - should you want to acquire a copy of her thesis. Attached is the full abstract of her Thesis.  


Improved recycling of the solid fraction of separated pig slurry, which is considerably
enriched in the essential plant nutrient phosphorus(P), could balance the P input in
differently used agricultural areas and reduce the unsustainable depletion of the
limited P rock reserves. By subsequent biological or thermal treatment, the P
concentration of the pig slurry-derived products isfurthermore increased, but these
processes are also expected to affect P availability from the respective products.
Consequently it was the overall objective of this PhD project to identify options for
upgrading the pig slurry solid fraction as well as investigating their impact on the
applicability of the product as P fertilizer. Special attention was moreover given to
the effect of the soil properties on the development of P availability over time.
In conclusion, both biological and thermal processing of pig slurry solids reduced P
availability in the initial phase after soil amendment. Only the solid fraction, had a
high initial P availability, which was within the same range as mineral P fertilizer, but
P availability decreased significantly within one growing season, whereas the
thermally processed materials had a more constant Pavailability. Due to a significant
enrichment of P and considerable reduction in volume, manure-derived char or ash
could easily be stored and transported to P-deficient agricultural areas, where it
could be applied as slow-release P fertilizer.

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