Development of a nutrient enriched biochar with the anaerobic liquid digestate from chicken manure and jack fruit waste

Abstract

Nutrient recovery from digestates through adsorption can be achieved by using biochar to concentrate essential nutrients (nitrogen phosphorus and potassium), thereby producing nutrient-enriched biochar. This study focused on optimizing the amount nitrogen, phosphorus and potassium that can be adsorbed from digestate obtained from jackfruit waste-based biochar. Response surface methodology using central composite design (CCD) was employed to determine the optimum adsorption conditions of adsorbent dose (20-70 mg/g) and contact time (48-120 hrs). Biochar was produced through pyrolysis while digestate was produced through anaerobic digestion. Results from the analysis of variance (ANOVA) revealed that the quadratic model best fits each of the responses. Adsorbent dose had the greatest influence on adsorption of each of the responses (p< 0.05). Contact time significantly affected adsorption of nitrogen (p< 0.05) but did not significantly affect the adsorption of phosphorus and potassium (p>0.05). The optimum adsorption conditions were 20 mg/g and 114.6 hrs for adsorbent dose and contact time respectively resulting in 17.44, 20.94 and 21.36 mg/g for nitrogen, phosphorus and potassium respectively. Biochar can be enriched with essential plant nutrients from the digestate before being applied as a soil amendment in the nutrient deficient soils.