Agro Fossil Free - Mineral concentrate from processed manure as fertiliser

General Description

A pilot study to determine the agronomic and environmental effects of the production and use of mineral concentrates was carried out in the Netherlands. Mineral concentrates are produced by reverse osmosis of the liquid fraction of separated livestock slurry. On average, 90% of the nitrogen (N) in mineral concentrate is present as ammonium-N, the other 10% as organic N. Pot experiments showed that the Nitrogen Fertiliser Replacement Value (NFRV) of injected mineral concentrate compared to calcium ammonium nitrate (CAN) was on average 91% and higher than that of injected pig slurry (75%). The average NFRV of injected mineral concentrate compared to CAN ranged from 72 to 84% in field experiments on arable land. The NFRV compared to CAN increased from 54% in 2009 to 81% on grassland, in 2014. The reason for the low NFRV in 2009 is not clear. The NFRV compared to liquid ammonium nitrate was higher (79–102%). Laboratory tests showed higher ammonia and nitrous oxide emissions from mineral concentrates than from CAN. Nitrate-leaching from applied mineral concentrates was similar or lower than that from CAN and untreated manure. There is scope to increase NFRV of mineral concentrate by use of low ammonia-emission application techniques, acidification, and reduction of organic N content of the concentrate. Scenario analyses showed that large scale use of mineral concentrate as fertiliser and solid fraction of separated slurry would decrease the need for mineral N and P fertilisers in the Netherlands.