Summary
Highlights
Alan Prinzhofer, a geologist and geochemist, introduces himself and his career, highlighting his significant work in natural hydrogen research. He explains his early career in natural gas, initially focusing on hydrocarbons like methane, ethane, and propane, and later expanding to non-hydrocarbon gases like CO2. His curiosity was piqued by forgotten papers on natural hydrogen, which was largely dismissed as non-existent at the time, leading him to pursue this 'exotic gas' a decade and a half ago.
Prinzhofer recounts his global search for natural hydrogen, discovering its presence in diverse geological formations across almost every continent, including Oman, the Philippines, New Caledonia, and Russia. His opportunity to work in Brazil led to the discovery of natural hydrogen evidence in numerous locations across the country, indicating its widespread presence.
Prinzhofer details the evolution of natural hydrogen detection, from rudimentary beginnings to current sophisticated methods. Exploration starts with superficial geology, identifying hydrogen seeps at the surface. This is followed by subsurface studies like geophysics, culminating in drilling wells to confirm its presence. He emphasizes the scientific challenges, such as understanding hydrogen genesis, migration, and accumulation, which are now being addressed through extensive research by academic and private institutions. The field has seen exponential growth in scientific papers and company involvement, from startups to major energy players, recognizing natural hydrogen as a significant new resource.
Natural hydrogen is confirmed to exist and be producible, as evidenced by pioneering efforts in Mali and recent discoveries in Australia. It offers a clean, renewable energy source present globally, and in some cases, replenishable at a human timescale. The estimated production cost of natural hydrogen, at $0.5 to $1 per kilogram, is significantly lower than manufactured hydrogen (gray and green). However, challenges remain in determining widespread producibility at this low cost and finding sources close to consumption areas to minimize transportation expenses.
Prinzhofer's recent work in Brazil reveals superficial evidence of a functional hydrogen system, notably the co-occurrence of hydrogen and helium seeping from the subsurface. Helium, a valuable byproduct with a highly tense market, is found in soils alongside hydrogen. The presence of helium, which can only originate from deep geological sources, validates the natural, deep-seated origin of the hydrogen, ruling out superficial or artificial contamination. Economically, even a small percentage of helium can render a hydrogen accumulation primarily a helium accumulation due to its high market value relative to hydrogen.
New methodologies are being tested to enhance exploration. Gamma spectrometry, specifically measuring thorium concentrations in soils, has emerged as an excellent proxy for hydrogen. Insar, a radar interferometry technique measuring continental movement, is also proving useful, as hydrogen activity can cause subtle rock movements. While traditional seismic reflection is relevant, passive seismic techniques are being adapted. Prinzhofer stresses the need for diverse tools to reduce exploration risk, as new methods are continuously being discovered and evaluated.
The economic viability of natural hydrogen is boosted by its low production cost ($0.5-$1/kg), significantly cheaper than gray ($2-$3/kg) and green ($5-$12/kg) hydrogen, which is currently a marginal 0.04% of total hydrogen production due to high costs. However, natural hydrogen is rarely 100% pure, requiring purification depending on its end use. Another challenge is transportation cost; natural hydrogen sources might be in remote locations, making it expensive to transport to consumption centers. While natural hydrogen appears globally, finding rich, producible accumulations near demand centers is crucial for economic feasibility, something that still needs further testing.
Prinzhofer addresses concerns about contamination in flux measurements. Human contamination is rare in the typically wild geological sites. Artificial hydrogen generation can occur from drilling, where metallic bits react with water at high temperatures. Associating hydrogen with helium from deep sources helps distinguish natural hydrogen from these artifacts. The idea of superficial biological hydrogen generation is scientifically debated, as soil microbiology often acts as a hydrogen sink rather than a source, consuming atmospheric hydrogen. Microorganisms have utilized hydrogen as an energy source for billions of years, preceding human discovery.
The understanding of hydrogen generation has evolved significantly. Fifteen years ago, serpentinization (alteration of oceanic crust rocks) was the primary imagined possibility. Today, chemical water reduction by iron, a common element, is considered the main process. Other reducers like sulfur, or radiolysis (breaking water molecules by natural radioactivity), are also being investigated. The relative importance of each process, and potential catalytic interactions, remains a research area. Prinzhofer draws a parallel to petroleum exploration a century ago, where production began long before the full understanding of its generation, suggesting that immediate production of natural hydrogen, regardless of full scientific understanding, is the key driver for its energy transition role.
While laboratory analytical techniques are advanced, the challenge lies in adapting them for field use. There's a critical need for miniaturization of equipment and ruggedization to withstand harsh environmental conditions (heat, humidity, rain). A key requirement is developing reliable perpetual hydrogen monitoring devices that can function for months without failure to record hydrogen flow variations. Existing geophysical tools from other fields need adaptation to natural hydrogen exploration, and new methodologies are constantly being tested to refine detection.
Hydrogen flux from soil to air can be highly variable due to superficial factors like atmospheric pressure, temperature, and soil humidity. This superficial variation, however, doesn't directly reflect the deeper, more consistent hydrogen flow that accumulates in reservoirs. The crucial parameter for commercial extraction is the average deep flow that fills and potentially refills accumulations, as seen in Mali. The surface measurements provide an indicator of a larger deep system, but the focus for economic viability is on understanding and accessing these stable deep flows.
Future research will focus on various stages of the hydrogen system: deep generation, efficient migration through rocks (as a small molecule, easily migrating), accumulation (whether strict seals are needed, or if 'bottlenecks' in permeability are sufficient, similar to traffic jams creating accumulations), alteration (as hydrogen is reactive), and leakage. Quantifying the relative importance of different generation processes and migration phases (dissolved in water vs. gas phase) is critical. Prinzhofer emphasizes that practical experience from industrial production will be paramount, providing data on pressure and gas composition evolution to guide scientific understanding. Close collaboration between industry and scientists is therefore crucial for the advancement of natural hydrogen exploration.
Prinzhofer expresses concern about the high cost of green hydrogen, particularly the electricity component, which makes 2/3 of its price. He questions the economic feasibility of green hydrogen unless electricity prices drastically drop. Gray hydrogen is cheaper but environmentally polluting. He believes natural hydrogen can play a vital role as a 'price reducer' by being mixed with green hydrogen, making the overall hydrogen energy more economically viable. Even if natural hydrogen cannot meet all global demands, it can significantly contribute to the hydrogen mix, ensuring hydrogen's place in the future energy landscape by improving its economic competitiveness.