Production and characterization of palm nut shells biochar for effective soil toxicity mitigation and crop productivity enhancement in Togo

Abstract

Palm nuts processing in the southern region of Togo generates large quantities of palm nut shell waste that poses environmental challenges. This study aimed to valorize palm nut shells by transforming them into biochar. The biochar was produced using an artisanal pyrolyzer. Its organic matter was determined using the loss-on-ignition method. Porosity and bulk density were respectively determined through water saturation and weighing. pH and electrical conductivity were measured using respectively pH meter and conductimeter.
Nitrogen and mercury contents were analyzed using respectively the Kjeldahl method and a Direct Mercury Analyzer. Phosphorus and potassium were measured using a flame photometer. Calcium, magnesium, sodium, copper, zinc, lead and cadmium were analyzed using Atomic Absorption Spectrophotometry. The results revealed that the biochar contained: Organic matter: 90.31%; Organic carbon: 52.51%; Porosity: 48.29 ± 0.85%; Bulk density: 0.402 ± 0.04 g/cm³; pH: 8.3; Electrical conductivity: 280 µS/cm. Nutrient content: Nitrogen: 1680
± 73.87 mg/kg; Phosphorus: 3573.4 ± 57.04 mg/kg; Calcium: 931.37 ± 69.27 mg/kg; Magnesium: 2144.18 ± 141.15 mg/kg; Potassium: 2767.69 ± 265.39 mg/kg; Sodium: 429.54 ± 37.02 mg/kg. Trace metals: Cadmium and mercury: Not detected; Lead: 0.65 ± 0.02 mg/kg; Copper: 23.13 ± 0.04 mg/kg; Zinc: 78.07 ± 0.11 mg/kg. These results show that palm nut shells biochar contains organic matter and minerals that are suitable to improve soil fertility, manage saline soils, and reduce bioaccumulation.