Assessing biochar and zeolite for enhanced agricultural sustainability of swine manure

Abstract

Swine manure is an alternative to synthetic fertilizers for providing crop nutrients. However, transportation costs, nutrient leakage, and gaseous emissions associated with using swine manure as fertilizer limit its agronomic benefits and cause environmental issues. In this study, we report the efficacy of nutrients (P as ortho-P and N as NH4+) recovery scheme from swine manure by batch equilibration and column leaching studies using different combinations of two biochars (untreated control biochar; control-BC and iron-modified biochar; iron-BC) and one zeolite with SiO2/Al2O3 = 30:1. Batch study employed different adsorbents (control biochar, followed by iron-BC, and zeolite) to obtain maximum adsorption (98.3% and 35.4%) and optimum desorption (66% and 18%) of P and N from the manure solution (1:5).A series of sand-matrix columns using the best combination of control-BC, iron-BC, and zeolite recovered 13,800mgkg-1 of P and 4,000mgkg-1 of N from manure solution after tenth cycles of leaching events. XRD and SEM-EDS analyses revealed the association of P with N and Mg, suggesting the adsorption of nutrients mostly through co-adsorption with manure colloids and precipitation as struvite. A series of soil-matrix column studies and a corn seed germination test were conducted to test the nutrient leaching/crop fertilization efficiencies using the recovered adsorbents. Inclusively, results showed that a proper combination of biochar and zeolite could effectively recover and concentrate nutrients from swine manure to develop crop fertilizer for easy transport and use in sustainable agriculture.