Valorization of Battery Material By-products: A Circular Economy Solution for Sustainable Manufacturing
Introduction: The Hidden Challenge Behind Green Energy
With the rapid growth of the electric vehicle market, the management of battery material by-products has emerged as a critical new challenge.The rapid expansion of the secondary battery industry for EVs and renewable energy storage has become a core driver of global decarbonation. However, this growth has also revealed a new challenge: the generation of a substantial amount of sodium sulfate (Na₂SO₄) as a by-product during raw material synthesis.Typically, the leaching and neutralization processes involving sulfuric acid and sodium hydroxide create a paradox. While batteries enable clean energy, their production process introduces environmental burdens that must be addressed. Without an effective Na₂SO₄ management solution, the sustainability of the battery industry remains incomplete.The research team at the Research Institute of Industrial Science & Technology (RIST) developed an integrated process that converts this waste into valuable products—sodium bicarbonate (NaHCO₃) and gypsum (CaSO₄·2H₂O). With technical support from SIMACRO, a process simulation model was established to enable digitalization.Published in the Chemical Engineering Journal, this research demonstrates how the synergy of digital engineering in process development enables the valorization of by-products generated during secondary battery material production into high-value materials.The study presents an industrial circular economy model that not only reduces the environmental impact of battery material manufacturing but also turns by-products into valuable resources.
Integrated Process Design for Battery Waste Valorization
The research team focused on developing a process that converts Na₂SO₄ into two industrially useful chemicals: sodium bicarbonate (NaHCO₃) and gypsum (CaSO₄·2H₂O). These substances hold market value across food, pharmaceutical, environmental, and construction sectors.This conversion process offers environmental and industrial benefits beyond waste reduction. During carbonation, carbon dioxide (CO₂) is directly reused as a reactant instead of being emitted. This demonstrates the practical application of carbon capture and utilization (CCU) within the process. The recovered gypsum also supports stable raw material supply in the cement industry, particularly as gypsum from flue-gas desulfurization declines with reduced coal-fired power generation. Previous attempts to valorize Na₂SO₄ faced three major limitations that hindered industrial implementation:
Particle size control – Industrial applications require specific particle sizes (typically 100–200 μm), yet achieving a consistent distribution was difficult.
Product purity – Commercial-grade applications demand purity levels above 99%, which previous processes struggled to achieve economically.
Wastewater management – Conversion processes produced effluents containing ammonium and sulfate ions, adding complexity and treatment costs.
At RIST, the team addressed all three challenges through an integrated process encompassing the entire pathway—from feedstock input to final product output and waste discharge. Through collaboration with SIMACRO, the process was digitally modeled, establishing a foundation for scaling and process design optimization.
Proposed process for NaHCO₃ and CaSO₄ production utilizing Na₂SO₄ byproduct generated from SBRMs manufacturing. ⒸChemical Engineering Journal, Volume 523
Three Key Innovations
1. Precision Particle Control through a Stepwise Process
The research team developed a two-stage reactor system that separates the carbonation and crystallization steps. This separation allows independent optimization of each step and resolves a fundamental issue: when carbonation and crystallization occur simultaneously, fluctuating reaction conditions result in broad and inconsistent particle size distributions.In the first stage, CO₂ is injected into a Na₂SO₄ buffer solution under controlled temperature conditions to prevent premature nucleation, forming a homogeneous supersaturated solution. In the second stage, this solution undergoes controlled cooling in a circulating crystallizer to promote uniform crystal growth.The results show substantial improvement. The single-stage process produced crystals with high variability (relative standard deviation 75%), whereas the two-stage system achieved uniform crystals with an average particle size of 100–200 μm and a relative standard deviation of 44%, meeting industrial requirements.
Particle size characteristics of synthesized NaHCO₃ and Na+/SO42− mole ratio remaining in the Na₂SO₄ solution under combined BCR and CCR operation: (a)PSD at the BCR temperature of 40 ◦C. The extracted solution was heated to 70 ◦C and then cooled to 40 ◦C in the CCR; (b) PSD at the BCR temperature of 70 ◦C. The extracted solution was maintained at 70 ◦C and then cooled to 40 ◦C in the CCR; and (c) temporal variations in VMD and product purity of NaHCO₃. (d) Na+/SO42− mole ratio in the Na₂SO₄ solution over time.ⒸChemical Engineering Journal, Volume 523
2. Achieving Commercial-Grade Product Purity
Product purity determines both the market applicability and value of the final product. The study demonstrated that a simple water-washing step effectively enhances product purity depending on the feedstock quality.When using industrial waste Na₂SO₄ (86% purity), the optimized washing process increased NaHCO₃ product purity to 95.4%, sufficient for industrial applications such as flue-gas desulfurization. When using high-purity Na₂SO₄ (99%) derived from battery material production, product purity reached 99.3%, meeting food and pharmaceutical-grade standards.This flexibility allows the process to be tailored to diverse raw material sources and target markets, improving economic feasibility under various operational scenarios.
3. Resource Recovery from Wastewater
After sodium bicarbonate separation, the remaining effluent contains residual chemicals requiring treatment. Instead of considering this as a disposal issue, the research team developed a method using calcium oxide (CaO) to recover ammonia while simultaneously producing gypsum as a high-value by-product.The process operates through pH adjustment and thermal treatment. Adding CaO increases the pH, converting dissolved ammonium into recoverable ammonia gas (95% recovery rate). Simultaneously, calcium ions react with sulfate ions to precipitate gypsum (85% removal rate). A secondary treatment step further increased gypsum purity to 97.1%, meeting industrial cement specifications.A key practical advantage is that CaO dissolution is exothermic, significantly reducing the external energy required for ammonia recovery and improving process economics.
NH4+ recovery and CaSO4 formation characteristics from wastewater generated after NaHCO₃ production as a function of wastewater temperature (40 ◦C, 60 ◦C, and 80 ◦C): (a) NH4+ recovery efficiency as a function of wastewater pH; (b) SO42− removal efficiency as a function of wastewater pH; and (c) XRD patterns of CaSO formed at different pH levels. ⒸChemical Engineering Journal, Volume 5234
Validating Feasibility through Process Modeling
Scaling laboratory results to industrial applications requires quantitative validation of material and energy balances, equipment sizing, and process parameters under varying operating conditions. To evaluate these complex interdependencies, process modeling and simulation play a critical role.
SIMACRO’s Contribution
SIMACRO contributed to the development of a comprehensive digital process model using Aspen Plus, one of the most established process simulation platforms, to evaluate the technical and economic feasibility of the RIST-developed integrated process.The simulation incorporated complex electrolyte chemistry, including multi-equilibrium reactions, salt formation pathways, and vapor–liquid equilibria for CO₂ and NH₃. This rigorous framework enabled precise prediction of pH, phase distribution, and mass balance across process units under specific operating conditions.
Key Simulation Outcomes
Modeling results quantitatively confirmed process feasibility. Processing 100 kg/h of Na₂SO₄ waste generated:
57 kg/h of NaHCO₃ (58% Na recovery)
80 kg/h of gypsum (84% sulfate recovery)
Beyond product yields, SIMACRO’s analysis identified critical opportunities for resource optimization:① Water management: The base process required 4.3 kg of water per kg of waste. However, recycled water from the final concentration step was sufficiently pure for reuse, reducing total consumption to 0.6 kg/kg—an 86% decrease, enabling near-zero liquid discharge.⓶ Solid waste minimization: By using high-purity feedstock and strategically recycling process streams, solid waste generation was reduced by 95% (from 0.49 kg/kg to 0.024 kg/kg of processed material).This modeling effort demonstrated SIMACRO’s digital engineering capabilities for sustainable process development and highlighted how advanced simulation bridges the gap between laboratory innovation and industrial implementation.
Realizing a Circular Economy through Battery Waste Valorization
This integrated valorization process offers a practical pathway for the battery industry to address Na₂SO₄ waste challenges while generating both economic and environmental value.
Economic and Environmental Benefits
The process transforms waste treatment costs into product revenue by recovering commercially valuable materials. Recycled ammonia can be reused within the process, reducing chemical consumption and operating costs. While a full techno-economic analysis remains essential for specific applications, the combination of waste minimization, product recovery, and resource efficiency presents a compelling economic case.Beyond waste reduction, the process also offers sustainability advantages:
Carbon utilization: CO₂ consumption during reaction aligns with CCU strategies, helping battery manufacturers reduce their overall carbon footprint.
Water conservation: Near-zero liquid discharge significantly mitigates environmental impact, especially in water-stressed regions.
Circular material flow: Converting linear waste streams into closed-loop cycles exemplifies circular economy principles, where one process’s waste becomes another’s raw material.
Scalability Pathways
The process employs established unit operations—bubble columns, crystallizers, and thermal strippers—common in chemical manufacturing, reducing technical risks during industrial scale-up. The validated simulation provides a reliable foundation for detailed engineering design and techno-economic optimization.
Outlook: Digital Engineering for Sustainable Industry
The Na₂SO₄ valorization project exemplifies how systematic process design and digital validation can transform environmental burdens into economic value, implementing circular economy principles at industrial scale.SIMACRO’s advanced modeling and simulation capabilities—integrated with process optimization and data management—enable computational validation of complex chemical processes prior to physical implementation, reducing technical risks and accelerating commercialization.As the battery industry continues to expand, companies that embed digital engineering into their operations will be better positioned in a carbon-constrained economy. The validated methodology here serves as a template applicable to chemical manufacturing, bioprocessing, and materials production, providing a foundation for converting sustainability goals into measurable, economically viable outcomes.
Key Summary
Battery precursor production generates large quantities of Na₂SO₄ waste with environmental and economic challenges.
The integrated process converts this waste into commercial-grade sodium bicarbonate (99% purity) and gypsum (97% purity).
The two-stage reactor system achieves industrial-scale particle size control with improved uniformity.
Wastewater treatment recovers 95% ammonia and 85% sulfate while producing valuable gypsum.
Process simulation validated an 86% reduction in water consumption, enabling near-zero discharge.
Digital engineering bridges the transition from laboratory innovation to industrial-scale circular manufacturing.
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This study was conducted by researchers at the Research Institute of Industrial Science & Technology (RIST) and published in the Chemical Engineering Journal (2025, Vol. 523).Research InformationDesignerWith headquarters in Boston and Seoul, SIMACRO has completed over 90 commercial modeling projects across 40 companies since 2018. Collaborating with global technology leaders such as AspenTech, Emerson, and OLI, SIMACRO is committed to advancing digital innovation in the process industry.About SIMACRODesigner