Nitrogen and phosphorus nutrient recovery from biomass slurry as value added fertilizer

Abstract

Biowaste materials could be considered a renewable source of fertilizer if methods for recovering Phosphorus from waste can be developed. Struvite precipitation and biochar was employed to remove nutrient composition from aqueous solutions of biogas slurry samples. The samples used included, that from poultry droppings, cow dung and pig dung digesters. Experiments with a biogas digester and aqueous solution were conducted at pH of nine, integration with NH4 + , Mg2+, and PO4 3- at molar ratio of 1.1. The chemical analysis was measured to find out the composition of the precipitate, and struvite was employed to remove the aqueous solutions. Struvite and biochar seed precipitation was studied as a simple, cost efficient method to remove nitrogen and phosphorus in high-strength biogas slurry streams. Controlled precipitates quickly removed nutrients and concurrently generate a valuable product for the fertilizer industry. Many factors influenced the precipitation of struvite such as component-ion molar ratios, pH, temperature, solids, and mixing energy. The impact of mixing, aeration and pH adjustment on the precipitation of struvite was studied in a laboratory controlled environment. Results showed that just pH and mixing energy can lead to some nitrogen and phosphorus removal efficiently. Laboratory results revealed a pH of 8-9 range over which maximum removal of phosphorus and nitrogen could be attained. The effect of solids in the slurry was also studied, and results showed no significant interference of solids removal of phosphorus, but visual inspection raised concerns about crystal propagation to form easily-settled solids