Production and life cycle assessment of jackfruit waste nutrient-enriched biochar for soil amendment and carbon sequestration

Abstract

Jackfruit, a globally consumed tropical fruit with economic and nutritional significance, has been extensively studied for the production of food products; however, there is a substantial gap in understanding and managing jackfruit waste. The primary objective was to enhance agricultural production and mitigate environmental pollution through the creation of biochar from jackfruit waste via pyrolysis and its subsequent enrichment through adsorption with nutrients from chicken-based digestate obtained from a functional fixed-dome anaerobic digester. The adsorption process was systematically investigated using adsorption, kinetics and thermodynamics models, and the optimization of adsorbent dose and contact time was conducted through response surface methodology. Subsequently, the study evaluated the impact of different biochar treatments on Nakati (Solanum aethiopicum) yields in greenhouse conditions, employing a completely randomized design. Furthermore, a comprehensive Life Cycle Assessment (LCA) was performed using Simapro software to analyze the environmental consequences associated with the production and utilization of nutrient-enriched biochar. The findings of the study showed that the Langmuir model appropriately described adsorption data with R2 of 0.9903, 0.0044 and 0.9916 for N, P and K respectively, indicating chemisorption as the predominant adsorption mechanism. The pseudo second-order model with R2 values of 0.9989, 0.9982 and 0.9910 for N, P and K respectively, provided a more accurate representation of the kinetics compared to the pseudo first-order model. The adsorption process was also found to be spontaneous (-ΔGo) and endothermic (+ΔHo). Optimal adsorption conditions entailed contact time of 114.6 hours and adsorbent dose of 20 g/100 ml. Generally, distinct soil amendments significantly (p<0.05) affected Solanum aethiopicum yields in the three planting seasons. The LCA outcomes indicated that the production of 1 kg of nutrient-enriched biochar is associated with 3.37 kgCO2eq emissions and carbon sequestration of 9.24, 9.80, 8.51, and 0.00 kg/ha for raw, nutrient-enriched, commercial, and no biochar treatments, respectively. In conclusion, this study showed that nutrient enrichment with biochar significantly enhances Solanum aethiopicum yields, from 23.26 g/plant for raw biochar to 39.25 g/plant for nutrient-enriched biochar. This research contributes valuable insights for improving soil properties and promoting sustainable agriculture in Uganda. Nevertheless, field trials should be done to assess different soil amendment effects on Solanum aethiopicum production under actual field conditions.