[Kim Byung-min's Science Village] The Dream of Reduction

Metal Objects That Require Endless Maintenance
Nature Must Be Cared for Like the Statue of Liberty

Byungmin Kim, Science Writer

In Manhattan, New York, symbolized as the heart of capital with finance circulating like blood through veins, there is another iconic symbol. One of the must-visit tourist spots in New York is the Statue of Liberty. About 15 years ago, the massive metal structure I encountered exuded a heavy verdigris hue, embodying the image of the United States as a “land of freedom and equality.” Was the use of metal meant to imply strength and eternity? However, the interior of the statue is constantly undergoing maintenance.

The statue’s outer shell is made of copper, and its internal framework is steel. The steel skeleton forms the bones, and hundreds of copper plates that make up the statue’s body are mounted and fixed onto this steel frame. The designer of the statue was French civil engineer Alexandre Gustave Eiffel. As you might guess from his name, he was the person who designed the Eiffel Tower. He was nicknamed the “Iron Magician” for his mastery of iron. However, chemically, the statue’s design is risky because the steel and copper plates were in direct contact. Of course, Eiffel, who was knowledgeable in chemistry, inserted oil-soaked asbestos between the two metals, indicating he was aware of the risk. But perhaps he overlooked that the statue would not be preserved in a museum environment. It has been exposed to the full force of natural elements such as seaside winds, salt, and lightning. This inherent flaw and weathering led to the need for large-scale repairs.

The reason is rust. Even I, who studied chemistry, sometimes mistakenly think iron will last forever. It is such a sturdy material that supports modern civilization. But iron structures are destroyed by rust. The only difference is that the speed of rusting is much slower than the speed of civilization’s destruction. Perhaps this is why iron implied “eternity.”

Natural history museums everywhere display civilizations in the order of Stone Age, Bronze Age, and Iron Age. Human history has only been properly recorded for a few thousand years. Thus, deeper civilizations without records of special events or figures are explained in connection with the materials used at the time. Although iron appeared much later than bronze, iron artifacts are not easily found in museums. Is it because iron was rare? No. Iron is the fourth most abundant element in the Earth’s crust after oxygen and silicon. Copper is even 26th. So traces of iron should remain somehow, as it was used for farming, hunting, and weapons. The reason pure iron does not remain is that it disappeared due to rust. The iron artifacts that remain today are alloys, which delayed their disappearance. Rust is the most common characteristic of metal chemical reactions, and iron is unique in rusting. Iron combines with oxygen, turns reddish, and expands. Like wounded skin forming a scab that peels off, the swollen rust separates from the surface and rust penetrates inward where new skin grows. Gradually, the iron’s form is destroyed and disappears. Like humans, iron is born with a fate to return to nature.

Photo by Asia Economy DB

In chemistry, rust is the phenomenon of metal losing electrons. The reason the metal maintained its body was because electrons filled between metal atoms, so when electrons are taken away, iron finds it difficult to maintain atomic arrangement. Chemistry defines the loss of electrons in a substance as an “oxidation reaction.” This explanation is difficult, so it is easier to talk about oxygen, which takes electrons. When metal meets oxygen and rusts, it is called “oxidation.” Originally, most metals existed scattered in minerals as metal oxides. Human intelligence extracted pure metals from minerals. But substances like oxygen do not leave these metals alone.

However, oxygen is only a representative destroyer that causes rust. For example, corrosion occurs even when two different metals are in contact. Each metal loses electrons to different degrees, and due to this difference, electrons move between different metals. The anode, which loses electrons, is gradually destroyed. This phenomenon was observed by 16th-century Italian physiologist Luigi Galvani. Even without chemistry knowledge, the electron movement between two metals in contact is not unfamiliar. It is the fundamental principle of batteries, which are a hot topic in electric vehicles today.

Humans have come to understand the properties and reactions of most metals well. We have relied on these metals to form the backbone of all civilizations and carry the hope of the future. But metals have lifespans and are destroyed. It is amazing that human civilization has lasted so far relying on incredible materials like iron. Of course, destroyed iron does not disappear. It originally existed as oxidized minerals, so it returns home. When iron oxide reacts with carbon, oxygen separates, electrons are gained, and pure iron is born. This chemical reaction is called “reduction,” the counterpart to “oxidation.” These terms were coined by modern scientists, but humans have known these phenomena for a long time, going back to the 30th century BCE.

Where iron began to be handled, environmental destruction accelerated. In the past, ironmaking consumed enormous amounts of wood. Today’s iron industry uses fossil fuels. Energy from fossil fuels melts iron ore and reacts carbon with oxygen to obtain pure iron, producing carbon dioxide as a byproduct. In fact, the iron and smelting industry has been a major cause of the climate crisis from the start. It accounts for about 8% of global carbon emissions. Yet, this method has been used until now. The abundance and efficiency of fossil fuels containing carbon meant there was no concern or even questions about alternatives. But now there is a reason to change. It has become difficult to guarantee sustainable human life. So, is there a way?

Usually, “selection and concentration” appear in such times. Humans have always been like that. We are strong in crises, and dreams become reality. For example, you may have heard of the hydrogen economy. The smallest element, the origin of all things, has emerged as a material that can save the world. Recently, hydrogen cars have been expected to play the role of an energy game changer. But hydrogen appears not only in driving cars but also in maintaining iron civilization and the environment. The iron industry aims to use hydrogen instead of carbon as a reducing agent. When oxygen is separated from iron ore (Fe2O3) by hydrogen (H2), pure iron (Fe) is obtained, and water (H2O) is produced as a byproduct. This narrative involves no carbon or greenhouse gases. This is called “hydrogen reduction ironmaking.” It is one of the dreams of reduction. Recycling is also important in metal reduction.

Fortunately, metals like gold, iron, and lead, which are relatively easy to recycle, have high reduction rates. If metals that have reached the end of their life are not recycled and reduced, they are discarded and lost in large quantities. According to a recent paper in Nature, more than half of the 61 metals supporting current civilization have an economic lifespan of less than 10 years. Key battery materials like lithium and cobalt, or semiconductor materials like gallium, have very high loss rates. Billions of tons of metals are mined every year, emitting greenhouse gases. For example, recycling aluminum requires only about 5% of the energy needed to mine and extract pure aluminum from ore. However, aluminum demand continues to increase, and aluminum production accounts for about 3% of global electricity consumption.

Of course, it is not as easy as it sounds. Regardless of the completeness of reduction technology, recycling costs and reducing agent production costs are often greater than the benefits gained from reduction. But we have become accustomed to judging everything by costs, benefits, economic value, and growth indicators. These are components of the growth equation. We are always overwhelmed by numbers, and experts who say it is difficult to realize this dream now may be better than we think. But if we have destroyed the world dreaming of growth until now, shouldn’t we pause growth with the dream of reduction? Although it cannot be expressed in numbers, our collective intelligence feels directly in life that this cannot continue. And I hope we do not forget the fundamental purpose of all our efforts. It is not only to sustain and grow human civilization’s landscape but also for the “sustainability and coexistence of the Earth’s environment and ecosystem.” The freedom and equality we so long for may be like the Statue of Liberty, a metal that requires endless care, and nature, our home, is also something humanity must constantly nurture. Of course, it will take a long time, but the remaining time does not seem abundant.

By Kim Byung-min, Adjunct Professor, Nano Convergence School, Hallym University

This content was produced with the assistance of AI translation services.