Green Hydrogen in Aluminum Production: Decarbonizing the Foundry

Introduction

The aluminum industry plays a vital role in global manufacturing, supplying materials for construction, transportation, and packaging. However, its production processes are energy-intensive and contribute significantly to carbon emissions, particularly through the use of fossil fuels. As the world shifts towards sustainability, green hydrogen emerges as a promising solution to decarbonize aluminum production, especially in foundries and recycling operations. This article explores the shift to green hydrogen as a sustainable fuel source, analyzing its potential, real-world applications, challenges, and future prospects.

Green hydrogen is hydrogen gas produced through the electrolysis of water using renewable energy sources, such as wind or solar power. Unlike gray hydrogen, which is derived from natural gas and emits carbon dioxide, green hydrogen is a clean energy carrier, emitting only water vapor when burned. This makes it an attractive option for industries seeking to reduce their carbon footprint. In aluminum production, green hydrogen can replace fossil fuels like natural gas in furnaces used for melting and refining aluminum scrap, offering a pathway to zero-emission production.

The focus of this analysis is on secondary aluminum production, or recycling, which is less energy-intensive than primary production but still relies on fossil fuels for heating. By integrating green hydrogen, the industry can significantly lower its greenhouse gas emissions, aligning with global efforts to combat climate change. This survey note delves into the current state of aluminum production, the basics of green hydrogen, its role in the industry, case studies, challenges, and future trends, ensuring a comprehensive understanding of this transformative shift.

Current State of Aluminum Production

Aluminum production comprises two main processes: primary production and secondary production (recycling). Primary production involves extracting aluminum from bauxite ore through the Hall-Héroult process, which uses electrolysis to reduce alumina (Al2O3) to aluminum metal. This process is highly energy-intensive, consuming approximately 13,000 to 15,000 kWh of electricity per ton of aluminum, and relies on carbon anodes, which are consumed and produce significant CO2 emissions.

Secondary production, or recycling, involves melting and refining aluminum scrap to produce new aluminum products. This process requires about 5% to 10% of the energy used in primary production, making it more energy-efficient. However, it still depends on fossil fuels, such as natural gas, for heating furnaces, contributing to carbon emissions. For instance, a typical aluminum recycling facility might emit around 1,000 to 2,000 kg of CO2 per ton of aluminum produced, depending on the fuel source and efficiency.

The environmental impact of aluminum production is substantial, with the global industry responsible for approximately 1% of total greenhouse gas emissions, according to the International Aluminium Institute. Given the growing demand for aluminum, driven by industries like automotive and construction, reducing these emissions is crucial. This is where green hydrogen offers a viable solution, particularly for the recycling sector, which is a growing part of the aluminum market.

Green Hydrogen Basics

Green hydrogen is produced through the electrolysis of water, a process that splits water (H2O) into hydrogen (H2) and oxygen (O2) using electricity. The key difference is that the electricity comes from renewable sources, such as wind turbines or solar panels, ensuring no carbon emissions during production. This contrasts with gray hydrogen, made from natural gas via steam reforming, which emits CO2, and blue hydrogen, which captures some of those emissions but still relies on fossil fuels.

The production process involves an electrolyzer, a device that uses an electric current to drive the reaction. There are several types of electrolyzers, including alkaline, proton exchange membrane (PEM), and solid oxide, each with varying efficiencies and costs. For green hydrogen, PEM electrolyzers are often preferred due to their flexibility and ability to handle variable renewable energy inputs.

The benefits of green hydrogen are clear. It is a zero-emission fuel when burned, producing only water vapor, making it ideal for industrial applications. It can also store energy from renewable sources, helping to balance the intermittent nature of wind and solar power. In the context of aluminum production, green hydrogen can serve as a direct replacement for natural gas in furnaces, providing the heat needed for melting without contributing to carbon emissions.

Current production costs for green hydrogen are higher than for gray hydrogen, typically ranging from $3 to $6 per kilogram, compared to $1 to $2 per kilogram for gray hydrogen, according to the International Energy Agency (IEA). However, as renewable energy costs decline and electrolyzer technology improves, these costs are expected to fall, making green hydrogen more competitive.

Role of Green Hydrogen in Aluminum Production

In aluminum production, green hydrogen’s primary role is as a fuel source in the furnaces used for melting and refining aluminum scrap during recycling. Traditional furnaces often burn natural gas, which releases CO2 and other greenhouse gases. By replacing natural gas with green hydrogen, the industry can eliminate these emissions, creating a decarbonized recycling process.

The process works by burning hydrogen in the furnace to generate heat, reaching temperatures necessary for melting aluminum, typically around 660°C (1,220°F). Hydrogen combustion produces water vapor (H2O) instead of CO2, ensuring no carbon emissions from the fuel source. This is particularly important for secondary production, where the energy demand is lower than primary production, making the transition to green hydrogen more feasible.

Beyond fuel, there is emerging research into using hydrogen as a reducing agent in aluminum production, similar to its role in steelmaking. However, for aluminum, the Hall-Héroult process relies on electrolysis, and replacing carbon anodes with hydrogen-based methods is still in early stages. For now, the focus is on using green hydrogen in furnace heating, where it can have an immediate impact.

The potential benefits are significant. A study published in “Sustainable Energy Technologies and Assessments” found that using green hydrogen in aluminum recycling can reduce CO2 emissions by 4,541 tons per year per facility, a substantial reduction (Green hydrogen integration). This aligns with industry goals to achieve net-zero emissions by 2050, as set by organizations like the Aluminium Stewardship Initiative.

Case Studies and Examples

Real-world applications provide valuable insights into the feasibility of green hydrogen in aluminum production. One notable example is Hydro’s trial in 2023, conducted at its extrusion plant in Navarra, Spain. Hydro, a leading aluminum company, collaborated with Hydro Havrand, its green hydrogen subsidiary, and Fives, an industrial engineering group, to test hydrogen-fueled production.

Hydro’s Trial

• Location: Navarra, Spain, at Hydro’s extrusion plant.
• Setup: Replaced natural gas with green hydrogen in the casthouses used for melting aluminum scrap.
• Results: Successfully produced a batch of aluminum billet with zero carbon emissions from the fuel source, marking the world’s first known industrial-scale trial (World’s first batch).
• Significance: Demonstrates the technical feasibility and potential for scaling up green hydrogen use in aluminum recycling.

The trial involved burning green hydrogen in furnaces to provide the heat needed for melting, achieving temperatures comparable to natural gas without emitting CO2. This success highlights the practical application of green hydrogen and its compatibility with existing furnace infrastructure, with modifications for hydrogen safety and combustion.

Economic Analysis

Another study, published in “Sustainable Energy Technologies and Assessments,” conducted a techno-economic analysis of green hydrogen integration in aluminum recycling (Green hydrogen integration). The study focused on a case study facility and found:

• Net Present Value (NPV): €57,370, indicating economic viability over the long term.
• Payback Period: 19.63 years, reflecting the high initial investment costs for green hydrogen infrastructure.
• CO2 Reduction: 4,541 tons per year, a significant environmental benefit.

While the payback period is lengthy, the study suggests that with policy support, such as subsidies for green hydrogen, and technological advancements, the economics could improve. This analysis underscores the potential for green hydrogen to be both environmentally and economically sustainable in the aluminum industry.

Challenges and Opportunities

Despite its promise, integrating green hydrogen into aluminum production faces several challenges. These include high production costs, infrastructure requirements, and scalability issues, but there are also significant opportunities for growth and innovation.

Challenges

1. Cost: Green hydrogen currently costs $3 to $6 per kilogram to produce, compared to $1 to $2 per kilogram for gray hydrogen, according to the International Energy Agency (IEA). This cost difference makes it less competitive for energy-intensive industries like aluminum production.
2. Infrastructure: The production, storage, and distribution of green hydrogen require significant investment. Electrolyzers, hydrogen storage tanks, and pipelines are needed, which may not be available in all regions.
3. Scalability: Scaling up green hydrogen production to meet the demands of the aluminum industry, which consumes vast amounts of energy, is a major hurdle. Current global production capacity is limited, with only about 0.1% of hydrogen being green, per the IEA.

Opportunities

1. Policy Support: Governments worldwide are offering incentives for clean energy, such as tax credits and grants for green hydrogen projects. For example, the European Union’s Hydrogen Strategy aims to install 40 GW of electrolyzer capacity by 2030, boosting supply (EU Hydrogen Strategy).
2. Technological Advancements: Ongoing research is improving electrolyzer efficiency and reducing costs. Innovations like solid oxide electrolyzers could lower energy consumption, making green hydrogen more affordable.
3. Market Demand: The growing demand for low-carbon aluminum, driven by regulations and consumer preferences, creates a market for green hydrogen. Industries like automotive, seeking lightweight and sustainable materials, are pushing for greener production methods.

Future Trends and Research Directions

The future of green hydrogen in aluminum production looks promising, with increasing investment and research aimed at overcoming current limitations. Several trends and research directions are shaping this landscape.

Future Trends

1. Increased Investment: Global investment in green hydrogen is rising, with companies and governments committing billions to projects. For instance, the U.S. Inflation Reduction Act provides tax credits for clean hydrogen production, expected to spur growth (Inflation Reduction Act).
2. Integration with Renewables: Combining green hydrogen production with renewable energy projects, such as offshore wind farms, can enhance efficiency. For example, projects like the North Sea Wind Power Hub plan to use excess wind energy for hydrogen production, potentially supplying aluminum foundries (North Sea Wind Power Hub).
3. Innovation in Processes: New furnace designs optimized for hydrogen combustion are being developed, improving heat transfer and efficiency. This could make green hydrogen more competitive with natural gas.

Research Directions

1. Optimizing Hydrogen Use: Research is focusing on optimizing hydrogen combustion in furnaces to ensure uniform heating and minimize energy loss. Studies at MIT are exploring hydrogen’s reaction rates with different materials, which could inform furnace design (MIT Energy Initiative).
2. Hybrid Systems: Investigating hybrid systems that combine hydrogen with other fuels, such as biogas, could reduce reliance on a single energy source and lower costs.
3. Life Cycle Analysis: Comprehensive life cycle analyses are needed to understand the total environmental impact of green hydrogen in aluminum production, including the energy used in electrolyzer manufacturing and hydrogen transport.

Conclusion

Green hydrogen offers a transformative opportunity to decarbonize the aluminum industry, particularly in the recycling sector, by replacing fossil fuels with a clean, zero-emission alternative. Real-world trials, such as Hydro’s 2023 test in Spain, demonstrate its feasibility, while economic analyses highlight its potential, despite challenges like high costs and long payback periods. As technology advances, policy support grows, and market demand increases, green hydrogen is poised to become a standard fuel source in aluminum production, contributing to a greener and more sustainable future.

Sources

• World’s first batch of recycled aluminium using hydrogen fueled production (World’s first batch)
• Green hydrogen integration in aluminum recycling: Techno-economic analysis towards sustainability transition in the expanding aluminum market (Green hydrogen integration)
• Using aluminum and water to make clean hydrogen fuel—when and where it’s needed (MIT Energy Initiative)
• EU Hydrogen Strategy (EU Hydrogen Strategy)
• Inflation Reduction Act (Inflation Reduction Act)
• North Sea Wind Power Hub (North Sea Wind Power Hub)