Abstrait

Sustainable Generation of Phosphate Based Fertilizers by Extraction from Biogenic Apatite

Maxmilla M

Phosphorus obtained from finite rock phosphate is one of the essential elements for food production and modern agriculture. Therefore, for sustainability of food supply and development in agriculture, management of phosphorus is key. Animal bones have a high concentration of phosphate that can be harvested and used in fertilizer production but they take many years to decompose and release the phosphate. This study set out to prepare bone phosphate enriched phosphoric acid from the otherwise discarded animal bones. Animal bones (predominantly cattle bones) were collected, washed, dried and crashed to smaller particles using a hammer after which they were ground in a mill. The ground bones were extracted with 0.275 M H3PO4 to give a 4.58 M bone phosphate-enriched phosphoric acid solution. Nitrogen was extracted from air by passing the air over heated copper filings and reacted with lithium to form lithium nitride. The lithium nitride was later hydrolysed to form ammonia which was reacted with the bonephosphate enriched phosphoric acid to generate the diammonium phosphate (NH4)2HPO4) fertilizer. The percent composition of nitrogen (Kjeldahl) in the diammonium phosphate was found to be 17.14% N while that of the phosphate was found to be 44.58% P2O5. The efficacy of diammonium phosphate in the growing of tomatoes in a greenhouse was determined with the commercially obtained diammonium phosphate as the positive control and no fertilizer as the negative control. Growth parameters of the tomatoes including plant heights, leaf length, leaf width and root length were obtained over a period of twelve weeks. The results showed that the growth parameters recorded for tomato plants grown with synthesized fertilizer were not significantly different from those recorded for tomato plants grown with commercial fertilizer (p-values = 0.000 <0.05). Based on the results obtained, it can be concluded that the bone phosphate based fertilizer prepared in this study was as efficacious as the commercial fertilizer. This is a significant finding in that it shows that it shows that animal bones can be converted into readily available phosphatic fertilizer.