Effectiveness of Biochar for Sorption of Ammonium and Phosphate from Dairy Effluent

The use of biochar for recovery of excess nutrients in dairy manure effluent and the use of nutrient-enriched biochar as soil amendment can offer a robust solution for multiple environmental issues. In this study we determined the capacity of biochar, produced by pyrolyzing mixed hardwood feedstock at 300 degrees C, to adsorb and retain or release two major nutrient ions: ammonium (NH4+) and phosphate (PO43-). We conducted the experiment using a range of nutrient concentrations that represent those commonly observed in dairy manure effluent (0-50 mg L-1 for PO43- and 0-1000 mg L-1 for NH4+). Up to 5.3 mg g(-1) NH4+ and 0.24 mg g(-1) PO43- was adsorbed from manure by biochar (18 and 50% of total amount in the manure slurry, respectively). During the desorption phase of the experiment, biochar retained 78 to 91% of the sorbed NH4+ and 60% of the sorbed PO43- at reaction times <24 h. Our findings confirm that biochar can be used for recovering excess nitrogen and phosphorus from agricultural water, such as dairy manure effluent.