Transforming extracted cashew nut shell into biochar and its application as soil amender for jute mallow (Corchorus olitorius L.) cultivation

This study addresses the environmental challenges posed by the waste generated during the extraction of cashew nut shell (CNS) liquid by proposing a sustainable repurposing method. Extracted CNS (waste) was pyrolyzed at varying temperatures to produce biochars, which were subsequently applied as soil amendments for the cultivation of jute mallow. Agronomic, proximate, physicochemical, mineral and antinutritional effects of the biochar and manure on the crop and soil were investigated. The produced biochars exhibited comparatively low volatile matter and ash contents, alongside high fixed carbon levels, indicating suitability for both soil amendment and energy-related applications with minimal environmental risk. Agronomically, biochar application alone increased number of leaves by ~ 50% compared to control. Post-harvest soil analysis revealed substantial improvements in phosphorus, organic matter, and nitrate contents. Proximate analysis of harvested jute mallow indicated increased protein content alongside reductions in ash and key antinutritional factors, particularly phytate and saponin. Although short-term biochar and manure application did not result in statistically significant changes in bulk soil physicochemical properties, they exerted pronounced positive effects on plant growth performance and nutrient dynamics. Overall, the findings demonstrate the potential of CNS-derived biochar as a sustainable soil amendment that enhances both soil quality and crop nutritional value.