Photo credit: FREEPIK
Stripping-scrubbing of the liquid fraction of pig manure allows for on farm production of biobased fertilizer. It starts with the liquid fraction of pig manure followed by scrubbing for ammonium salt recuperation.
The operating principle of stripping-scrubbing is that ammonia (NH3) is stripped by air, steam or vacuum through the nitrogen rich waste stream in an NH3 stripping reactor, resulting in NH3 transfer from the aqueous phase to a gas phase. The released NH3 is removed in a chemical air scrubber by washing it with a strong acidic solution such as nitric acid (HNO3), resulting in ammonium nitrate. The efficiency of process can be increased by adjusting the pH and/or temperature by which more of water soluble NH4-N ion will be converted into the gaseous ammonia.
The resulting fertiliser is liquid and can be applied as any other liquid fertilizer through injection or through spraying followed by immediate ploughing. Applications where the fertiliser is brought as close as possible to the roots is ideal. This fertiliser is best applied at the start of the growing season because the nitrogen in the product is present as ammonium and it still needs to be converted to nitrate before the plant can absorb it. This type of fertiliser is useful for any kind of crop, but in case a S containing counter acid is used in the production step the resulting fertiliser can be of particular interest for crops that also have a sulfur need such as cabbage crops, onions, celery, grains, sugar beets etc.
As this fertiliser has an acidic character special attention should be paid to the material use when applying this fertiliser. Also, at any time the mixture with animal manure should be avoided as toxic H2S formation could occur.