An investigation into the technical feasibility and social acceptance of biochar-based remediation for crude oil polluted soils

Abstract

Crude oil spills have remained a major cause of environmental devastation in Nigeria’s Niger-Delta region despite efforts by government and industry professionals to remedy the situation. Over the last decade, carbonaceous sorbent-based technologies such as biochar have been advancing and employed increasingly in developed countries. Biochar remediates contaminants by making them biologically unavailable to receptors and has been proposed as a cost-effective option for organic contaminant remediation. This research therefore aims to evaluate the viability of coconut shell activated biochar as a sustainable technology solution for the remediation of petroleum contaminated soils in Nigeria from a scientific as well as social point of view. This is achieved through empirical comparison of biochar-based remediation with bioremediation, risk assessment and a critical analysis of the factors which influence biochar technology implementation in Nigeria and the USA. This combination of technical and social perspectives seeks to enable a more comprehensive understanding of the factors which influence the implementation of a new remediation technology in Nigeria. Microcosm experiments compared remediation of artificially-polluted biochar-amended soils with soils treated by biostimulation. Biostimulation which involves the use of microbes to degrade contaminants with the aid of added nutrients has been widely used in Nigeria. Laboratory results showed that biochar-amended microcosms had significantly lower volatilization flux (t-test p ˂ 0.05) than those without biochar during the period of active volatilization. Relatively high amount of residual oil were observed in biochar-amended microcosms, but passive sampling experiments showed that biochar amended batches had significantly lower available concentrations of oil in the aqueous phase than unamended batches. Partition coefficient (Kd) values derived from the batch study were used as input for risk assessment modelling using the United Kingdom’s CLEA (Contaminated Land Exposure Assessment) tool. Risk assessment modeling and experimental results demonstrated the importance of incorporating bioavailability assumptions into risk management decisions. The Mirror Lake restoration project in Delaware, USA was used as a case study for exploring the social acceptance of the new technology by highlighting the factors which impacted on its implementation in the USA and comparatively analysing them with those of relevance in Nigeria. Factors identified include remediation challenges, technical requirements, cost considerations, pollution typology, risk considerations & regulatory concerns. The main obstacles to the implementation of the technology in Nigeria that were identified include lack of enabling legislation, inefficiencies and corruption within the regulatory framework; as well as the prevalence of highly contaminated sites and ongoing contamination