Material and Substance Flow Analysis of Used Lead Acid Batteries in Nigeria: Implications for Recovery and Environmental Quality.

Background: As resources become scarce, information from material and substance flow analysis can help to improve material recovery policy. The flow of toxic substances such as lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As) and antimony (Sb) can be used as a basis for appropriate risk management decisions for optimum environmental quality.

Objectives: The present study examined a material and substance flow analysis of used lead acid batteries (ULAB) from motor vehicles and implications for environmental quality in Nigeria.

Methods: Information on motor vehicle imports was obtained from the literature. Mathematical models were constructed and used for the material and substance flow analysis. Samples of 50 brands of ULAB pastes were digested using a microwave digestion system followed by elemental determination (Pb, Cd, silver (Ag), As, cobalt (Co), calcium (Ca), Cr, copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), Sb, selenium (Se), and tellurium (Te)) with inductively coupled plasma optical emission spectroscopy.

Results: Approximately 4.8 million tons (Mt) lead acid batteries (LAB) from vehicles was used in Nigeria between 1980 and 2014, out of which approximately 2.6 Mt had reached end-of-life (EoL) stages. From the total amount in EoL, approximately 2.3 Mt was recycled, and 0.3 Mt was landfilled. Among the toxic elements, Pb, Cd and As were the most abundant in ULAB; and of the valuable elements, Fe and Cu had the highest levels. Approximately 3.5 Mt of Pb was used in the past (1980-2014) in ULAB for motor vehicles, out of which approximately 1.9 Mt tons was in EoL stages.

Discussion: The results revealed that the battery pastes were heterogeneous. Only Pb exceeded the total threshold limit concentration (TTLC) of 1000 mg/kg. The TTLC describes the safe levels or concentration of heavy metals in the environment. The levels observed for other metals in this study were below the TTLC values. The present study estimated an average life span for lead acid batteries in motor vehicles in Nigeria of 5 years, suggesting an additional 2.2 Mt at EoL by 2019. High concentrations of Pb in air, water and soil carry the potential for contamination of food products, especially in Nigeria, where food is traditionally prepared and sold in open air markets in an unregulated manner.

Conclusions: High amounts of toxic elements present in the various life cycle stages signal potential environmental and human health hazards.

Competing interests: The authors declare no competing financial interests.