Turning Trash into Power: MIT’s Hydrogen Breakthrough

A Simple Aluminum–Water Process Could Deliver Green Hydrogen without Greenhouse Gases

By Rick Laezman*

Aly Kombargi (left) and Niko Tsakiris of MIT work on a reactor setup that generates hydrogen gas by mixing aluminum pellets, seawater, and caffeine. Tony Pulsone, courtesy of Aly Kombargi

What if the world’s clean energy revolution could be powered by its garbage?   

A team of Massachusetts Institute of Technology (MIT) engineers has unveiled a deceptively simple process that extracts hydrogen—one of the cleanest fuels on earth—by mixing seawater, coffee grounds, and scrap aluminum.  

Currently, the extraction of hydrogen from its natural state often involves the use of fossil fuels that emit large quantities of greenhouse gases. But the MIT process produces no emissions—and might just unlock hydrogen’s long-awaited promise as a fuel source.  

Why Hydrogen? 

Hydrogen, the most abundant element in the universe, is found in nature as a trace atmospheric gas (H₂) or tightly chemically combined with other elements. 

It is used as a fuel in two ways: It can be burned in an internal combustion engine, just like gasoline in a car. It can also be used in a fuel cell, which generates an electrical current by combining hydrogen with oxygen electrochemically, without combustion. The fuel cell is the cleaner method of the two because its only by-product is water.  

A prototype electric car at MIT powered by an aluminum-seawater hydrogen generator. Courtesy of Aly Kombargi

In either case, hydrogen first must be extracted from various compounds and captured before it can be consumed as a fuel source. The most common and efficient large-scale production methods create what’s called gray hydrogen because they rely on the burning of fossil fuels, which generate emissions. For example, the most common of these, the steam–methane reforming method, generates hydrogen by combining steam with the methane contained in natural gas. While it is the most cost-effective method for separating hydrogen, it also produces carbon dioxide, the most prevalent of greenhouse gases.

MIT’s aluminum–seawater hydrogen generator is built into a prototype electric bike. Courtesy of Aly Kombargi

In contrast, green hydrogen captures the full potential of hydrogen as a clean fuel by separating the gas through processes generated by other clean resources. For example, electrolysis uses an electrical current to separate hydrogen from water molecules. When the electricity that it uses is itself generated by renewable sources, like the sun or the wind, the process is sustainable and completely emissions-free throughout its life cycle (excluding, of course, emissions generated by the construction of solar panels and wind turbines and the mining of the materials that compose them).

Of course, green hydrogen has become a highly prized resource as society pursues emissions-free energy generation. These methods are especially valuable when they can be done at large, commercial scale. Capturing large volumes of hydrogen for consumption without generating any greenhouse gases represents the ideal solution to the dual challenge of rising global energy demand and rising atmospheric and oceanic temperatures.

Toward that end, the researchers at MIT are confident that they have advanced a viable method for extracting green hydrogen.

How Does It Work?

Aly Kombargi is a recent graduate from MIT with a PhD in mechanical engineering and the lead author of the study in the August 2024 issue of Cell Reports Physical Science, which first described the MIT research. He partnered with fellow MIT students Brooke Bao and Enoch Ellis, and MIT Professor of Mechanical Engineering Douglas Hart.

Kombargi was looking for “a way to make hydrogen that could be generated on demand and consumed close to where it is needed.”

A illustration of MIT's aluminum–water reaction that produces hydrogen gas (H–H or H₂) and is catalyzed by caffeine (imidazole). Courtesy of Aly Kombargi

Kombargi told The Earth & I that the project appealed to him because he was looking for “a way to make hydrogen that could be generated on demand and consumed close to where it is needed.” This distributed approach to hydrogen, much like rooftop solar panels and small, residential wind turbines, would make the resource more easily dispatched in remote and off-grid locations by avoiding the costly, energy-intensive limitations of bulk hydrogen generation, such as high-pressure storage, cryogenics, and the need for a large supply of electricity.

If their project proved to be successful, added Kombargi, they would have “a compact, dispatchable ‘solid hydrogen carrier’ that works even off-grid or at sea.”

The process he and his colleagues employed relies on the aluminum–water reaction (AWR). Aluminum is a highly reactive metal that aggressively grabs the oxygen atom in water (H₂O), releasing hydrogen gas (H₂) and forming aluminum oxide, a highly versatile industrial compound, while generating heat.

The AWR is not a new concept. In fact, it is more than 100 years old. The concept of producing hydrogen from the reaction of metals with water was first proposed by American chemist G.F. Barker in his paper entitled “On Alloys of Gallium and Aluminum,” which was published in 1880 in the American Journal of Science. It has remained a subject of study ever since.

To make their scrap aluminum reactable with water, however, the MIT researchers had to overcome a significant hurdle. Because of aluminum’s reactivity, it bonds with oxygen in the air, creating a superthin shield of aluminum oxide on the metal’s surface.

To break the oxide shield, Kombargi and his team used gallium–indium, a rare-metal alloy that effectively scrubs aluminum of its oxide. Similar to mercury, the alloy has a very low melting point, often below room temperature, so that it can be used as a liquid metal that can adhere easily to other surfaces. Unlike toxic mercury, the alloy is considered a safer alternative in many applications.

For their research, the MIT engineers treated aluminum with gallium–indium to prepare it for the AWR. For the H₂O component, they used seawater instead of freshwater, which added another positive element to their experiment. They discovered that the salt in the water helped to recapture the gallium–indium, which could be reused to generate yet more hydrogen, lowering the cost of the process and making the cycle more sustainable.

With a low concentration of imidazole, a structural component of caffeine, they could produce the same amount of hydrogen in just five minutes, compared with two hours without it.

Not satisfied with the initial results of their experiment, the MIT researchers made an additional refinement. After testing out different kitchen and laundry products, they discovered that Dunkin’s coffee sped up the process. They determined that, with a low concentration of imidazole, a structural component of caffeine, they could produce the same amount of hydrogen in just five minutes, compared with two hours without it.

Comparing Emissions

Because the appeal of hydrogen as a fuel lies in its lack of carbon emissions as well as in its abundance, the MIT researchers set out to conduct a “life cycle study” to determine how emissions-free their process really is.

Depending on the emissions produced during the extraction–transportation–consumption life cycles of hydrogen produced by various means, the gas is denoted by the colors green, gray, blue, black, brown, yellow, white, pink, and even turquoise. Only green hydrogen is completely life-cycle emissions-free.

A video showing the process for producing hydrogen gas from aluminum and seawater.

The engineers performed their analysis using Earthster, an online life cycle assessment tool that draws data from a large repository of products and processes to determine their associated carbon emissions. They found that the most cost-effective scenario consists of generating 1 kilogram (2.2 lbs) of hydrogen—which can drive a car 60 to 100 kilometers (about 40 to 60 miles)—using recycled aluminum (instead of mined aluminum) combined with seawater (rather than freshwater). This process emits about 1.45 kilograms of carbon dioxide for every kilogram of hydrogen produced. They note that by comparison, fossil-fuel-based processes emit 11 kilograms of carbon dioxide per kilogram of hydrogen generated. They add that their process is also “on par” with other green hydrogen technologies powered by solar and wind energy.

The process is also cost effective. The researchers’ analysis calculated the cost of the fuel produced at about $9 per kilogram, which they point out is comparable to the price of hydrogen that would be generated with other green technologies. (By comparison, gray hydrogen (from natural gas) costs $1.50–$2.50 per kilogram to produce.)

Scaling Up 

Eventually, the researchers hope their process could be scaled up to generate hydrogen in large volumes, thereby lowering the cost for consumers. For example, Kombargi envisions a production chain starting with scrap aluminum sourced from a recycling center. The aluminum would be shredded into pellets and treated with gallium–indium. Capitalizing on the stored energy potential of the treated aluminum, drivers could transport the pretreated pellets as aluminum “fuel,” rather than directly transporting hydrogen, which is highly flammable.

The pellets would be transported to a fuel station, ideally situated near a source of seawater, which could then be mixed with the aluminum to produce hydrogen. As study author Kombargi told The Earth & I, “Aluminum is energy-dense, stable to transport as a solid, and globally available, including as scrap.” This makes it an ideal candidate to transport as stored hydrogen energy to remote locations where generating hydrogen would otherwise be difficult, impractical, or impossible using conventional methods. Consumers could pump the gas into their cars powered by either an internal combustion engine or a fuel cell.

Along those lines, Kombargi and his team are developing a small reactor that could run on a marine vessel or underwater vehicle. If successful, the technology offers a promising method to provide reliable energy for remote communities and disaster relief, and it can make use of recycled aluminum while reducing the need for other, more harmful methods of energy production.

As society strives to find plentiful and practical sources of fuel for increased energy production while also reducing carbon emissions, hydrogen deserves all the attention it receives. Methods like the aluminum–water reactor could be the right approach to bring hydrogen into the mainstream.

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*Richard Laezman is a freelance writer in Los Angeles, California. He has a passion for energy efficiency and innovation. He has been covering renewable power and other related subjects for more than 10 years.