Bio-stimulation with Fresh Avocado Seed for crude oil Remediation with a Bio-kinetic Modelling

Abstract

The remediation of crude oil-contaminated soils requires sustainable and cost-effective solutions. This study investigates the performance of fresh avocado seed (Persea americana) as a biostimulant for the remediation of Bonny Light crude oil-contaminated soil from the Kalarugbana community, Niger Delta. A 56-day laboratory-scale experiment was conducted using bioreactors containing 1 kg of soil contaminated with 100 ml of crude oil and treated with different volumes of fresh avocado seed slurry (0 ml as control, 100 ml, 200 ml, and 300 ml). Microbial growth (CFU/g) and Total Petroleum Hydrocarbon (TPH) depletion (mg/kg) were monitored weekly. Results demonstrated a strong positive correlation between inoculants volume and efficacy. Microbial counts increased from 5,000 CFU/g to 114,000, 135,000, and 170,000 CFU/g for the 100 ml, 200 ml, and 300 ml treatments, respectively. This enhancement directly drove TPH depletion from an initial 3,729.7 mg/kg to 1,202.4, 1,038.1, and 647.7 mg/kg, corresponding to degradation efficiencies of 67.76%, 72.17%, and 75.33%. The control reactor showed only minimal natural attenuation (38.3%). A biokinetic model was developed from first principles, relating substrate depletion to remediator concentration. Model simulations in MATLAB, using an equilibrium rate constant (K-eq) of 0.0083 week⁻¹, produced results in strong agreement with the experimental data. This work confirms that fresh avocado seed is a highly effective, low-cost biostimulant, with its efficiency directly scalable to the volume applied. The validated model provides a predictive tool for optimizing remediation strategies.