An estimated 5 billion tons of gold are dissolved in Earth's oceans, roughly 20,000 times all the gold humanity has ever mined. If it could be extracted economically, that cost might set a ceiling on gold prices. About a century ago, even a Nobel Prize-winning scientist tried this and gave up. Now the Japanese heavy industry giant IHI is taking on the challenge, using algae.

The Gold Price Surge and the Promise of "Oceanic Gold"

Gold prices have been soaring relentlessly. Driven by geopolitical risks and inflation concerns, prices have risen roughly tenfold compared to 20 years ago.

Humanity has mined approximately 180,000 tons of gold throughout history, enough to fill about 3.8 Olympic swimming pools. The remaining economically recoverable reserves are estimated at around 50,000 tons, roughly one pool's worth. This scarcity has long underpinned gold's value.

But shift your perspective, and everything changes. The world's oceans contain an estimated 5 billion tons of dissolved gold, more than 20,000 times the total of all gold ever mined plus future recoverable reserves. If technology could extract this oceanic gold economically, its production cost would theoretically set gold's price ceiling.

IHI's "Biosorption" Breakthrough

Yasuyuki Fukushima, a principal researcher at IHI Corporation (formerly Ishikawajima-Harima Heavy Industries), has spent over a decade developing technology to extract gold from seawater.

His solution is "biosorption": using living organisms to adsorb and recover metals from water. The key player is cyanobacteria, a primitive type of algae.

Gold in seawater exists as dissolved compounds like gold chloride. When gold chloride encounters certain components in cyanobacteria, a chemical reaction occurs: the chlorine detaches, and the gold returns to its metallic form. The algae essentially "liberates" the gold. Because gold has the lowest ionization tendency of any metal, it adheres to the algae far more readily than other metals.

The cyanobacteria Fukushima uses is a wild species discovered in a hot spring in northeastern Japan. It had adapted to extreme conditions, water temperatures above 50°C and alkaline pH. Fukushima, whose expertise is in ceramics rather than biology, obtained the algae through collaborative research in 2017 and successfully cultivated it through self-study.

Proven Results: Hot Springs and Deep-Sea Vents

The technology has already moved to demonstration phase.

A research team from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and IHI conducted gold recovery experiments at Tamagawa Onsen in Akita Prefecture. They processed the cyanobacteria into special sheet-like adsorbent materials and immersed them in the hot spring water. The result: approximately 30 grams of gold per ton of sheet material, an extraordinary yield considering that major gold mines worldwide typically extract only 3 to 5 grams per ton of ore.

From 2021 to 2023, the team also conducted experiments near hydrothermal vents roughly 700 meters below sea level off Aogashima Island, Tokyo. When they retrieved the sheets in June 2023, they had adsorbed gold equivalent to about 20 grams per ton. This site, discovered by University of Tokyo researchers in 2015, has hydrothermal temperatures of 240-260°C, ideal conditions for gold and silver precipitation.

The Nobel Laureate Who Gave Up

The dream of extracting gold from the sea is nothing new. Nearly a century ago, Nobel Prize-winning scientist Fritz Haber tried, and failed.

Haber, who won the 1918 Nobel Prize in Chemistry for synthesizing ammonia from atmospheric nitrogen (the Haber-Bosch process), hoped to help pay Germany's massive World War I reparations by extracting gold from seawater.

Initially, Haber estimated he could extract 65 milligrams of gold per metric ton of seawater. But his surveys revealed the actual concentration was less than one-thousandth of his estimate. The project was abandoned as economically unviable.

The Ultimate Barrier: "Lake Chuzenji for One Gram"

The technology works. So why hasn't it been commercialized?

The answer lies in concentration. Gold exists in seawater at roughly 10 parts per quadrillion, or about one ten-millionth of a gram per ton of seawater, by some estimates.

To illustrate this, Fukushima calculated that recovering just one gram of gold would require processing a volume of water equivalent to Lake Chuzenji, Japan's famous lake with a surface area of 11.9 square kilometers.

In laboratory conditions, 5 grams of cultivated algae (from a 5-liter culture) can adsorb up to 0.5 grams of gold. But that's with artificially concentrated gold solutions. In actual seawater concentrations, "perhaps only one hundred-thousandth, maybe one millionth, will adhere," Fukushima admits.

When they tested in actual ocean conditions, the algae sheets were eaten by crabs and sea cucumbers, and degraded by microorganisms. Deep-sea deployment preserves the sheets better but dramatically increases recovery costs.

Fukushima is candid: "For seawater gold extraction to be economical, gold prices would need to be about 100 times higher." With gold currently trading around ¥27,000 (roughly $180) per gram in January 2026, profitability remains distant.

The Near-Term Path: Hot Springs and Mine Wastewater

Currently, Fukushima is seeking partner companies. Rather than seawater, the practical first step is applying the technology to water sources with relatively high gold concentrations, hot spring water or mine wastewater.

"Once we determine where to operate, we can optimize the technology for that specific environment," Fukushima explains. With the right location, he believes commercial success is achievable.

Global Research Progress

Research on extracting gold from seawater is advancing worldwide.

In 2024, a team from East China University of Science and Technology proposed using reduced graphene oxide membranes (rGOM) for gold extraction, integrated with seawater desalination processes. Their rGOM can selectively adsorb 99% of gold ions while barely capturing other common seawater elements, maintaining stability for over 30 days.

In the United States, researchers are developing composite materials combining metal-organic frameworks (MOFs) with polymers for gold extraction. Some have reported successful gold recovery from Mediterranean seawater.

However, all approaches face the same fundamental challenge: the extremely low gold concentration in seawater. Developing adsorbent materials with high capacity and selectivity that can handle concentrations below 20 parts per trillion remains a global challenge.

Will Gold Ever Stop Being "Precious"?

Fukushima offers a different perspective on gold's true value:

"Gold doesn't rust, and it conducts electricity extremely well. Its physical properties are excellent. There are many industrial applications where we'd like to use more gold, it's just too expensive."

If oceanic gold becomes accessible, the situation transforms entirely. Gold would have effective reserves comparable to copper or iron. Beyond investment and jewelry, its superior physical properties could enable widespread industrial applications.

A Nobel laureate's abandoned dream is being revived by Japanese researchers wielding algae. Will gold prices rise a hundredfold first, or will technology break through the cost barrier? Either way, the day when gold becomes an "extractable resource" may be drawing nearer.

In Japan, surging gold prices have renewed interest in seawater gold extraction technology. What discussions exist in your country about utilizing ocean resources or finding new gold sources? We'd love to hear your thoughts!

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