Valorization of Animal Bone-derived Biochar for pH Modulation and Nitrate Accumulation during Bioremediation of Petroleum-contaminated Soils
Ejike Immaculate Ugochi
World Bank Africa Centre of Excellence for Oilfield Chemicals Research, University of Port Harcourt, Choba, PMB 5323, Port Harcourt, Rivers State, Nigeria.
Ogugbue Chimezie Jason
World Bank Africa Centre of Excellence for Oilfield Chemicals Research, University of Port Harcourt, Choba, PMB 5323, Port Harcourt, Rivers State, Nigeria and Department of Microbiology, University of Port Harcourt, Choba, PMB 5323, Port Harcourt, Rivers State, Nigeria.
Onojake Mudiaga C. *
World Bank Africa Centre of Excellence for Oilfield Chemicals Research, University of Port Harcourt, Choba, PMB 5323, Port Harcourt, Rivers State, Nigeria, Petroleum and Environmental Chemistry Research Group, Department of Pure and Industrial Chemistry, University of Port Harcourt, Choba, PMB 5323, Port Harcourt, Rivers State, Nigeria and Institute of Natural Resources, Environment and Sustainable Development (INRES), University of Port Harcourt, Choba, PMB 5323, Port Harcourt, Rivers State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Crude oil contamination significantly disrupts soil physicochemical properties, reducing fertility, impairing microbial activity, and hindering nutrient cycling. This study examined the effect of animal bone-derived biochar on soil pH and nitrogen dynamics (ammonium, nitrate, and organic nitrogen) during the bioremediation of crude oil-polluted soil. A Randomized Complete Block Design (RCBD) was employed using uncontaminated soil, crude oil-contaminated soil (5% w/w), and contaminated soils amended with 20g, 60g, and 100g biochar. Soil pH and nitrate concentrations were monitored over 90 days alongside microbial assessments. Results showed that crude oil contamination slightly elevated baseline pH (4.95) compared to uncontaminated soil (4.85) but impeded nitrification, with NO₃⁻ levels as low as 2.40 mg/kg. Biochar amendment significantly (p < 0.05) increased pH in a dose-dependent manner, with the highest treatment reaching 7.51 by Day 90, aligning with FAO/USDA optimal ranges (6.0–7.5). Similarly, NO₃⁻ accumulation improved markedly, peaking at 37.20 mg/kg in the 100g biochar treatment, compared to 2.00 mg/kg in unamended contaminated soil. Results also showed that biochar amendments significantly increased NH₄-N and TON levels in contaminated soils in a dose-dependent manner. At Day 0, ammonium concentrations in contaminated soil were 0.70 mg/kg, which rose to 9.91 mg/kg with 100g biochar. Similarly, TON increased from 0.098% in contaminated soil to 0.291% in soil with the highest biochar concentration. The alkaline nature and mineral content of bone biochar contributed to pH stabilization, hydrocarbon toxicity reduction, and restoration of favorable microbial habitats. The study demonstrates that valorization of animal bone-derived biochar, significantly improves the chemical balance and biological activity of degraded land, showcasing the transformation of animal waste into a valuable amendment for restoration of petroleum-contaminated soils. The approach offers a sustainable, and cost-effective pathway for soil rehabilitation and agricultural recovery in oil-impacted regions such as the Niger Delta.
Keywords: Biochar, crude oil contamination, nitrate dynamics, soil pH, bioremediation