Trends in Hydrogen as an energy resource- SDG 7
Ensure access to affordable, secure, sustainable, and modern energy
Arturo Peñas Jiménez
Ingeniero de Minas
The different sources of hydrogen production have been classified according to a color code. So-called “green” hydrogen, which is the cleanest, is produced by electrolysis of water powered by renewable energies. This ideal method is expensive, so most of the hydrogen produced in the world is generated by a cheaper process called steam reforming, which uses natural gas as a feedstock and generates CO2 from the reaction of methane with water. This is “gray” hydrogen, which does not contribute to climate change mitigation because it still requires fossil fuels to obtain. However, “gray” hydrogen can be transformed into “blue” hydrogen when the CO2 generated is captured by carbon storage technologies (CCUS). The most common is “blue” which is extracted from natural gas. Currently, only 2% of the world’s hydrogen is “green”, but only 0.1% comes from the electrolysis of water.
Recently, publications have appeared in the journal “Science” that speaks of “golden” hydrogen that would lead to negative emissions and clean up the atmosphere. Researchers from the Institute of Chemical Technology of CSIC and the Polytechnic University of Valencia announced in the spring of 2022 that they had created a “golden” hydrogen generator. Based on proton ceramic, it is scalable and modular. That is, it could be manufactured in different sizes to meet demand.
Specifically, it is an electrified reactor to obtain hydrogen in a more sustainable and energy-efficient way using 36 individual ceramic membranes in a scalable and modular generator that produces hydrogen from electricity and various fuels with almost zero energy loss. The fuel can be ammonia, natural gas, biogas, or other hydrogen-containing molecules. The project has made it possible to scale up an electrified reactor to a production of about half a kilo of pressurized hydrogen per day by electro-compression, with high purity and maximum energy efficiency of over 90%. Another advantage is that the CO2 generated is not emitted into the atmosphere but is transformed into a pressurized stream for liquefaction and transport for subsequent use or storage, thus enabling decarbonization. The next step will be to put what has been learned into practice and scale it up to generate golden hydrogen on an industrial scale.Another avenue noted in the journal would be to obtain “natural” (geological) hydrogen directly from underground resources. Contrary to conventional wisdom, large reserves of natural hydrogen may exist worldwide, like oil and gas, but not in the same settings. Researchers say that water-rock reactions deep in the Earth continually generate hydrogen, which seeps through the crust and sometimes accumulates in subway traps. There could be enough natural hydrogen to meet growing global demand for thousands of years, according to a U.S. Geological Survey (USGS) model designed in October 2022 at a meeting of the Geological Society of America.
In Bourakébougou (Mali) Chapman Petroleum in 2012 and under the direction of Denis Brière analyzed what came out of a dry well drilled for water, concluding that it was gas with 98% hydrogen. This was extraordinary as it was thought that it could not occur in nature.
Following the Malian experience, the number of publications on “natural” hydrogen has exploded. Dozens of start-up companies have appeared, many in Australia, which are acquiring rights to explore hydrogen. In 2019, the first hydrogen well was completed in the United States in Nebraska. Enthusiasm for natural hydrogen has emerged as interest in a clean, carbon-free fuel has grown. Governments are pushing it as a way to combat global warming, efforts galvanized when Russia invaded Ukraine last year, triggering a rushed search, especially in Europe, for alternatives to Russian natural gas. At the moment, all commercial hydrogen has to be manufactured either in a polluting way, using fossil fuels, or in a costly way, using renewable electricity. Natural hydrogen, if it forms substantial reserves, could be there for the taking, giving experienced drillers in the oil and gas industry a new environmentally friendly perspective.
Natural hydrogen can be not only clean but also renewable. It takes millions of years for buried and compressed organic deposits to turn into oil and gas. In contrast, natural hydrogen is always produced anew, when groundwater reacts with iron ores at elevated temperatures and pressures. In the decade since hydrogen extraction wells began in Mali, the flows have not diminished. It is still the early days for natural hydrogen. Scientists do not fully understand how it forms and migrates and, more importantly, whether it accumulates in a commercially exploitable way.
We run into storage problems, along with a lack of pipelines and distribution systems. Pressurized tanks add weight and cost. Liquefying hydrogen requires cooling it to -253°C, generally a disqualifying expense.
Brière says extraction in Mali, which benefits from shallow wells of nearly pure hydrogen, could be as cheap as 50 cents per kilogram. Ian Munro, CEO of Helios Aragon, a start-up looking for hydrogen in the foothills of the Spanish Pyrenees, says its break-even costs could end up between 50 and 70 cents.
To guide decision-making, policymakers, resource managers, exploration companies and investors will need information on the extent of these potential resources. However, at present, the uncertainties associated with the generation, migration, accumulation, and preservation of H2 in the subsurface make it impossible to accurately determine these resources.
According to Geoffrey Ellis (US Energy Resources Program), despite the uncertainties, we know something about the presence and behavior of H2 in the subsurface. Additional inferences about this presence of H2 can be made by employing knowledge gained from studies of fluid migration, accumulation, and preservation related to geologic resources such as petroleum, geothermal energy, noble gases, etc. These factors can be combined to provide more light on the possible magnitude of geologic H2 resources in the subsurface.
A preliminary model has been developed to assess these resources using a mass balance approach. Model inputs include surface flux, capture efficiency, trap residence time, and biotic and abiotic consumption of H2.
The Earth is currently assumed to be in a steady state concerning H2 flux from the subsurface to the atmosphere. The hydrogen consumption of this future H2 production is modeled as a function of historical natural gas production. The results of the stochastic model indicate a greater than 98% probability that geological H2 production will satisfy at least 50% of the predicted green H2 production by the year 2100.
Furthermore, this model indicates that H2 residence time in reservoirs and annual H2 flux to the atmosphere have the greatest influence on these resource potentials, while the effects of biotic and abiotic H2 consumption have little effect. These results provide an initial framework and suggest that further investigations are warranted to evaluate these potential natural H2 resources.
Arturo Peñas Jiménez