System analysis with life cycle assessment for NiMH battery recycling

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Nickel metal hydride (NiMH) batteries are crucial for electric vehicles, solar power, and tools.
• These batteries contain valuable strategic raw materials like cobalt, nickel, and rare earth elements (REEs).
• Developing sustainable recycling processes for NiMH batteries is essential for resource recovery and environmental protection.

Purpose of the Study:

• To compare the environmental and economic sustainability of different NiMH battery recycling options.
• To evaluate the recovery of REEs from NiMH battery anode material.
• To consider projected market developments in the sustainability assessment.

Main Methods:

• Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) methods were applied.
• Two hydrometallurgical processes for REE recovery were compared: sulfation roasting and hydrochloric acid leaching with oxalate precipitation.
• Recycling processes were benchmarked against primary REE extraction from Chinese sources.

Main Results:

• The hydrochloric acid leaching process demonstrated superior environmental and economic performance compared to sulfation roasting.
• The use of oxalic acid in the hydrochloric acid process significantly impacts its overall sustainability footprint.
• For the sulfation roasting process, energy, sodium hydroxide, and sulfuric acid consumption were the main contributors to the environmental footprint.

Conclusions:

• Hydrometallurgical recycling of NiMH batteries offers a more sustainable alternative to primary REE extraction.
• Process optimization, particularly regarding chemical usage like oxalic acid, is critical for maximizing the benefits of NiMH battery recycling.
• The study highlights the importance of integrated approaches combining scientific and systemic perspectives for sustainable metal management.