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RECYCLING OF SPENT LITHIUM-ION BATTERIES WITH NIGERIAN AGRICULTURAL WASTE AS GREEN REDUCTANTS
Abstract
The rapid adoption of lithium-ion batteries (LIBs) in portable electronics, electric vehicles, and renewable energy storage has led to a significant increase in spent battery waste globally and in Nigeria. Improper disposal and inadequate recycling of these batteries result in environmental contamination with heavy metals (lithium, cobalt, nickel, manganese), toxic electrolytes, and organic compounds, posing serious risks to soil, water resources, human health, and ecosystems. Conventional recycling methods, pyrometallurgy and hydrometallurgy, are energy-intensive, generate secondary emissions or hazardous waste, and often rely on expensive or environmentally harmful reagents. Green and sustainable alternatives are urgently needed, particularly in developing countries with limited recycling infrastructure. This thesis investigates the recycling of spent lithium-ion batteries using Nigerian agricultural wastes (such as cassava peels, rice husks, palm kernel shells, orange peels, and sugarcane bagasse) as green reductants in hydrometallurgical processes. These bio-wastes are rich in reducing sugars, phenolic compounds, and organic acids that can serve as eco-friendly reducing and chelating agents to recover valuable metals (Co, Ni, Li, Mn) from cathode materials. Through characterization of spent batteries and agricultural wastes, leaching experiments, optimization of process parameters, metal recovery assessment, and comparative environmental and economic analysis, the study aims to develop a low-cost, low-emission, and locally adaptable recycling approach that promotes circular economy principles, reduces environmental pollution, and adds value to agricultural residues in Nigeria.
CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
The global transition toward electrification and renewable energy has driven exponential growth in lithium-ion battery (LIB) production and consumption. In Nigeria, the increasing penetration of mobile phones, laptops, solar home systems, and electric two- and three-wheelers has resulted in a rising accumulation of end-of-life LIBs (Obaje et al., 2023). Unlike developed economies with established collection and recycling systems, Nigeria currently lacks formal LIB recycling infrastructure, leading to informal dismantling, open burning, and indiscriminate disposal in landfills and dumpsites (Adewuyi et al., 2024).
Spent LIBs contain valuable metals such as cobalt (5–20%), nickel (5–10%), lithium (2–7%), manganese (5–15%), and copper, alongside toxic components including organic electrolytes, polyvinylidene fluoride (PVDF) binder, and graphite (Harper et al., 2019; Yao et al., 2021). Improper management releases heavy metals and fluorine compounds into soil and groundwater, causing long-term ecological damage and health risks including neurological disorders, respiratory problems, and carcinogenicity (Zeng et al., 2023).
Conventional recycling routes pyrometallurgy (high-temperature smelting) and hydrometallurgy (acid leaching followed by precipitation/solvent extraction) recover valuable metals but are energy-intensive, emit greenhouse gases and toxic fumes, and often require large quantities of strong mineral acids (H₂SO₄, HCl) and reducing agents (Na₂S₂O₅, H₂O₂) (Chen et al., 2023; Li et al., 2024). These characteristics make them economically and environmentally challenging for developing countries.
In recent years, green hydrometallurgical approaches using organic acids (citric, lactic, ascorbic) and bio-reductants have gained attention for their lower environmental footprint (Musariri et al., 2023). Agricultural wastes abundant in Nigeria—cassava peels, rice husks, palm kernel shells, orange peels, corn cobs, and sugarcane bagasse are rich in reducing sugars, phenolic compounds, carboxylic acids, and lignocellulosic materials that can act as natural reductants and chelating agents during leaching of cathode materials (LiCoO₂, NMC, LFP) (Akinyele et al., 2024; Ogunmodede et al., 2023).
Studies have shown that bio-wastes can effectively reduce Co(III) to Co(II) and facilitate metal dissolution under mild conditions, achieving high leaching efficiencies while significantly reducing acid consumption and secondary waste generation (He et al., 2023; Zhang et al., 2024). In the Nigerian context, utilizing agricultural residues for LIB recycling aligns with waste valorization, circular economy principles, and sustainable development goals by simultaneously addressing two major waste streams: spent batteries and agricultural by-products.
This study explores the potential of Nigerian agricultural wastes as green reductants in the recycling of spent lithium-ion batteries, aiming to develop a low-cost, environmentally benign, and locally viable recovery process.
1.2 Statement of the Problem
Nigeria generates increasing volumes of spent lithium-ion batteries from consumer electronics, solar systems, and emerging electric mobility, yet there is no formal recycling system in place (Adewuyi et al., 2024). Most end-of-life batteries are dismantled informally, burned openly, or discarded in uncontrolled dumpsites, leading to release of cobalt, nickel, lithium, and toxic electrolytes into the environment (Obaje et al., 2023).
Conventional recycling technologies are not feasible in Nigeria due to high capital investment, energy requirements, emission of greenhouse gases and dioxins (pyrometallurgy), and dependence on imported chemicals and reducing agents in hydrometallurgy (Chen et al., 2023). These methods are also associated with significant secondary waste generation and high operational costs, making them unsuitable for developing economies with limited technical and financial capacity (Zeng et al., 2023).
Meanwhile, Nigeria produces millions of tonnes of agricultural residues annually, including cassava peels, rice husks, palm kernel shells, and fruit peels, that are largely underutilized, burned, or left to decompose, contributing to air pollution, greenhouse gas emissions, and land degradation (Ogunmodede et al., 2023).
The lack of integrated, green, and low-cost recycling approaches for spent LIBs, combined with the under-exploitation of abundant agricultural wastes as process reagents, represents a missed opportunity for resource recovery, environmental protection, and sustainable industrial development in Nigeria (Akinyele et al., 2024).
This study addresses these gaps by investigating the use of Nigerian agricultural wastes as green reductants in the hydrometallurgical recycling of spent lithium-ion batteries.
1.3 Objectives of the Study
The main objective is to investigate the recycling of spent lithium-ion batteries using Nigerian agricultural waste as green reductants.
Specific objectives are:
- To characterize the physicochemical composition of spent lithium-ion batteries and selected Nigerian agricultural wastes
- To evaluate the leaching efficiency of valuable metals from spent battery cathodes using extracts and derivatives of agricultural wastes as reductants
- To optimize key process parameters and assess the recovery of cobalt, nickel, lithium, and manganese
1.4 Research Questions
- What are the major metal contents and structural characteristics of spent lithium-ion battery cathode materials collected in Nigeria?
- Which Nigerian agricultural wastes exhibit the highest reducing capacity and metal leaching performance when applied to spent battery recycling?
- What are the optimal conditions (reductant dosage, acid concentration, temperature, time) for maximum recovery of cobalt, nickel, lithium, and manganese using selected agricultural waste-based reductants?
1.5 Significance of the Study
This research contributes to the development of a sustainable, low-cost, and environmentally friendly method for recycling spent lithium-ion batteries in Nigeria. It promotes the valorization of abundant agricultural residues, reducing open burning and landfilling of bio-wastes. The approach can decrease dependence on imported chemicals, lower energy consumption, and minimize secondary pollution compared to conventional methods. Successful implementation could support the establishment of local recycling enterprises, create jobs, recover strategic metals, and reduce environmental and health risks associated with improper battery disposal. The findings may also inform policy on extended producer responsibility (EPR), waste management regulations, and circular economy strategies in Nigeria.
1.6 Scope and Limitations
The study focuses on spent lithium-ion batteries collected from consumer electronics and solar systems in Nigeria, and on selected agricultural wastes (cassava peels, rice husks, palm kernel shells, orange peels). It covers characterization, leaching with bio-reductants, parameter optimization, and metal recovery at laboratory scale. Industrial-scale process design, long-term economic feasibility, detailed life-cycle assessment, and full regulatory compliance analysis are beyond the scope. Variations in battery chemistry, waste composition, and seasonal availability of agricultural residues may limit generalizability.
1.7 Definition of Terms
- Spent Lithium-Ion Battery (LIB): End-of-life rechargeable battery whose capacity has significantly declined and is no longer suitable for its original application.
- Green Reductant: Naturally derived organic material (from agricultural waste) that reduces metal ions during leaching without generating harmful by-products.
- Hydrometallurgy: Metal recovery process involving leaching with aqueous solutions followed by separation and purification.
- Leaching Efficiency: Percentage of target metal extracted from solid material into solution.
- Circular Economy: Economic system aimed at eliminating waste and continually using resources through reuse, recycling, and recovery.
References
Adewuyi, A. P., Oyetunji, A., & Oladipupo, A. R. (2024). Environmental and health risks of informal spent lithium-ion battery recycling in Nigeria. Journal of Environmental Management and Safety, 5(1), 45–58.
Akinyele, O. A., Ogunmodede, O. T., & Adebayo, G. B. (2024). Valorization of cassava peels as a reducing agent in metal recovery processes: A review. Waste and Biomass Valorization, 15(3), 1123–1139.
Chen, M., Ma, X., Chen, B., Arsenault, P., Bernard, P., Binnemans, K., … & Zhao, Y. (2023). Recycling end-of-life electric vehicle lithium-ion batteries. Joule, 7(9), 1978–2003.
Harper, G., Sommerville, R., Kendrick, E., Driscoll, L., Slater, P., Stolkin, R., … & Walton, A. (2019). Recycling lithium-ion batteries from electric vehicles. Nature, 575(7781), 75–86.
He, L., Zhang, G., Zhang, S., & He, Y. (2023). Bioleaching of spent lithium-ion batteries using organic acids from agricultural waste. Journal of Cleaner Production, 415, 137856.
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Musariri, M., Ogunmodede, O. T., & Manyuchi, M. M. (2023). Bio-reductants for sustainable leaching of critical metals from spent lithium-ion batteries. Sustainable Chemistry and Pharmacy, 34, 101201.
Obaje, S. O., Adeyemi, O. O., & Ibrahim, M. (2023). Current status of lithium-ion battery waste management in Nigeria: Challenges and prospects. African Journal of Environmental Science and Technology, 17(6), 210–223.
Ogunmodede, O. T., Adebayo, G. B., & Akinyele, O. A. (2023). Utilization of agricultural residues as reducing agents in hydrometallurgical processes: A Nigerian perspective. Environmental Science and Pollution Research, 30(28), 72145–72160.
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