Hydrogen is increasingly recognized as a key element of future energy sustainability, offering the potential for a drastic reduction in greenhouse gas emissions. Its ability to release only water as an energy source, without harmful carbon compounds, places it at the center of global decarbonization efforts. Despite these remarkable properties, the dominant methods of hydrogen production today rely heavily on fossil fuels, thereby burdening the entire life cycle of this energy carrier with a significant ecological debt. This paradox of "dirty" production of "clean" fuel represents one of the main obstacles on the path towards a truly green hydrogen economy.

Innovative approach to hydrogen production from MIT

Recent scientific breakthroughs offer light at the end of the tunnel. A team of experts from the Massachusetts Institute of Technology (MIT) has presented a revolutionary process that could fundamentally change the way we produce hydrogen, significantly reducing its carbon footprint. Their method, which has attracted the attention of the scientific community and industry, uses readily available materials: seawater and recycled aluminum cans, with the addition of a small amount of a specific metal alloy. Last year, researchers demonstrated the basic concept at a laboratory level, showing that it is possible to generate hydrogen gas by combining these components, even including caffeine in some early experiments to study the impact of different substances. However, the key question that then arose was whether this promising procedure could be efficiently transferred from laboratory conditions to an industrial scale and what its actual environmental impact would be when all production and distribution steps were taken into account.

To answer these critical questions, scientists conducted a comprehensive life cycle assessment (LCA), a methodology that evaluates the environmental impacts of a product or process "from cradle to grave." This detailed study covered every segment of the process in potential industrial application. Carbon emissions associated with the procurement and processing of aluminum, the chemical reaction of aluminum with seawater to produce hydrogen, and the transport of the produced fuel to end-users, for example, to gas stations where drivers could refuel their hydrogen cars, were precisely calculated. The results showed that this new approach could generate only a fraction of the carbon emissions characteristic of conventional, fossil fuel-based hydrogen production methods.

Minimal carbon footprint confirmed by study

In the study, whose results were recently published in the prestigious journal Cell Reports Sustainability, the team reported that for every kilogram of hydrogen produced by this process, only 1.45 kilograms of carbon dioxide would be generated throughout the entire life cycle. This figure becomes particularly impressive when compared to traditional methods, such as steam methane reforming, which emit about 11 kilograms of carbon dioxide for every kilogram of hydrogen obtained. Such a low carbon footprint ranks the new technology alongside other proposed "green" hydrogen production methods, such as water electrolysis powered by solar or wind energy, positioning it as a serious contender in the race for sustainable hydrogen production.

"Our results show that we are on par with existing green hydrogen technologies," said lead author of the study, Dr. Aly Kombargi, who recently received his PhD from MIT in mechanical engineering. "This work highlights the enormous potential of aluminum as a clean energy source and offers a scalable pathway for implementing low-emission hydrogen in the transportation sector and for powering remote energy systems." Alongside Dr. Kombargi, co-authors of the study from MIT include Brooke Bao, Enoch Ellis, and Professor of Mechanical Engineering Douglas Hart, whose expertise contributed to the development and evaluation of this innovative process.

The science behind the process: How aluminum releases hydrogen

At first glance, immersing an aluminum can in water does not cause a vigorous chemical reaction. The reason for this is that aluminum, when exposed to oxygen from the air, instantly forms a thin but very resistant protective layer of aluminum oxide. This passivation layer prevents further reaction of the metal. However, if this layer were removed or breached, pure aluminum exhibits exceptional reactivity with water. Under such conditions, aluminum atoms efficiently break down water molecules (H₂O), forming aluminum oxide (or its hydrated forms such as boehmite) and, most importantly, releasing pure hydrogen gas (H₂). A significant advantage of using aluminum lies in its high energy density.

"One of the main advantages of using aluminum is its energy density per unit volume," explains Dr. Kombargi. "With a very small amount of aluminum fuel, it is theoretically possible to provide a significant portion of the energy needed to power a hydrogen vehicle."

Innovative method for aluminum activation

Over the past year, Dr. Kombargi and Professor Hart have perfected an aluminum-based hydrogen production recipe. The key to their success lies in the method of breaching aluminum's natural protective layer. They discovered that by treating aluminum with a small amount of gallium-indium, an alloy containing the rare metals gallium and indium, they could effectively "clean" the aluminum surface, exposing the pure metal. After such treatment, the researchers mixed pellets of thus prepared aluminum with seawater and observed an immediate and abundant production of pure hydrogen. Additionally, it was shown that the presence of salt in seawater helps in the precipitation and separation of gallium-indium after the reaction. This means that this valuable alloy can be collected and reused in subsequent hydrogen production cycles, making the process not only more sustainable but also more economically viable due to reduced consumption of expensive metals.

"When we presented the scientific basis of this process at conferences, the most common questions we received were about cost and carbon footprint," recalls Dr. Kombargi. "So we decided to conduct a comprehensive analysis to get a clear picture."

Sustainable cycle and economic perspective

In their new study, Dr. Kombargi and his colleagues conducted a detailed life cycle analysis to quantify the environmental impact of hydrogen production using aluminum, tracking every step – from the source of aluminum to the transport of the final product, hydrogen. For practical illustration and comparison, they chose the production of one kilogram of hydrogen as a reference unit. "With one kilogram of hydrogen, a fuel cell car can travel between 60 and 100 kilometers, depending on the efficiency of the fuel cells themselves," notes Dr. Kombargi, emphasizing the practical relevance of this quantity.

The analysis was conducted using a specialized software tool, Earthster, an online life cycle assessment platform that uses an extensive database of products, processes, and their associated carbon emissions. The team considered several different scenarios for hydrogen production using aluminum. They compared the use of "primary" aluminum, obtained by bauxite mining and energy-intensive processing, with the use of "secondary" aluminum, obtained by recycling waste aluminum products such as cans. They also analyzed different methods of transporting aluminum and the produced hydrogen.

After evaluating a dozen different scenarios, the one with the lowest carbon footprint was identified. This optimal scenario is based on the use of recycled aluminum – a raw material whose use significantly reduces emissions compared to primary aluminum production – and seawater, a natural resource that, in addition to being readily available, also allows for efficient separation and recycling of gallium-indium, thereby saving resources and reducing costs. It was found that this scenario, viewed in its entirety, from raw material procurement to hydrogen delivery, would generate approximately 1.45 kilograms of carbon dioxide per kilogram of hydrogen produced. They also calculated that the price of fuel produced in this way would be about 9 US dollars per kilogram, which is competitive with the prices of hydrogen that would be produced by other green technologies, such as those using wind or solar energy.

Vision for commercial application and further development

Researchers predict that if this low-carbon process is advanced to a commercial level, the production chain could look something like this: it would begin with the collection of waste aluminum from recycling centers. This aluminum would then be shredded into small pellets and treated with a gallium-indium alloy. One of the significant advantages is that drivers or distributors could transport these pre-treated aluminum pellets as "aluminum fuel," instead of directly transporting hydrogen, which as a gas is volatile, requires special high-pressure tanks or cryogenic conditions, and is potentially hazardous to handle. These pellets would be transported to "hydrogen stations" ideally located near a source of seawater. At these stations, the aluminum pellets would be mixed with seawater as needed, generating hydrogen on-site. The end-user could then directly pump the produced gas into their vehicle, whether it's a car with an internal combustion engine adapted for hydrogen or a fuel cell vehicle.

The entire process also generates an aluminum-based byproduct, the mineral boehmite (aluminum oxyhydroxide, γ-AlO(OH)). Boehmite is a valuable industrial raw material often used in the production of semiconductors, electronic components, catalysts, refractory materials, and as a filler in plastics and rubber. Dr. Kombargi points out that if this byproduct were collected after hydrogen production, it could be sold to manufacturers of these materials, thereby further reducing the overall costs of the hydrogen production process and increasing its economic sustainability.

"There are many aspects to consider," says Dr. Kombargi. "But the most exciting part is that the process works. And we've shown that it can be environmentally sustainable."

The group of scientists continues to further develop and refine this process. They recently designed a small, portable reactor, about the size of a water bottle, that uses aluminum pellets and seawater to generate hydrogen. The amount of hydrogen produced is sufficient to power an electric bicycle for several hours. They have previously demonstrated that the process can produce enough hydrogen to power a small car. The team is also actively exploring the possibilities of applying this technology underwater, working on the design of a hydrogen reactor that would use surrounding seawater to power small vessels or underwater vehicles, opening new horizons for autonomous underwater operations. This research is partly supported through the MIT Portugal Program, an initiative that promotes collaboration and innovation.

Source: Massachusetts Institute of Technology