Scientists at the University of Pretoria (UP) are leading a study of natural H₂ gas discovered under the Earth’s surface in Mpumalanga—a source of renewable energy that could contribute to the national energy budget and help address the energy shortage in South Africa.

While it is still too early to know how much of an effect the discovery could have on the country’s national energy landscape if exploited, the scientists have envisaged small “stand-alone” generation units (powering generators with a capacity of about 20 kilowatts) for local domestic or minor industrial use. However, recent stories in Europe suggest that some natural H₂ resources might be much bigger than originally thought.

“There might well be an untapped renewable, non-polluting energy supply that has gone unnoticed for centuries, right under our noses!” said structural geologist Professor Adam Bumby. “Only in the past few years have geoscientists started to measure natural H₂ flux out of the Earth, and we have already demonstrated that this is the case in parts of Mpumalanga. Our local scientists, with their geological and geophysical knowledge of the potential source rocks, combined with the expertise of our European partners, are proving to be a successful team.”

Prof Bumby added that they are in the process of identifying potential source sites, after which they will be able to quantify estimated resources.

“The role of this project is to indicate the presence of H₂, and how it could be incorporated into the national energy budget if it were to be exploited.” This discovery was made as part of the HyAfrica project undertaken by a consortium of partners within the European Union (EU) and African Union (AU).

Recent samples taken in Mpumalanga currently fall under the natural/white H₂ category. Follow-up field trips and isotopic comparisons of all the H₂ samples collected will provide a clearer understanding of the geological controls responsible for generating H₂ in Mpumalanga. According to Prof Bumby, it is difficult to estimate at this point how long it will take to properly exploit any decent reserves of H₂.

He added that H₂ is considered a fuel of the future due to it emitting zero emissions.

“It can be used, for instance, in car engines instead of petrol, producing water as the exhaust gas. H₂ is the most common element in the solar system, but sadly most of it is either sitting or burning in the sun. H₂ can also be synthesized from water using electrolysis, but it requires a lot of energy to split water.”

The energy to produce H₂ fuel by electrolysis of water can be sourced from renewables (such as solar energy or wind turbines) and is called green H₂. Alternatively, the energy needed for the split can be sourced by burning fossil fuels (gray H₂), but that produces carbon dioxide, which is a greenhouse gas. If that greenhouse gas is captured and stored (sequestered), it’s called blue H₂.

Natural H₂ (or white H₂) is different because the energy needed to break the H₂ from water is provided by geological processes through chemical reactions in rocks driven by high temperatures at depth in the Earth’s crust (serpentinization). The decay of radioactive elements in some minerals deep within the Earth’s crust can also result in H₂ being split off from water (radiolysis).

“Because these reactions and processes are occurring relentlessly in some geological environments, the H₂ that is produced by these natural processes can be considered renewable,” Prof Bumby explained. “Because H₂ is a very light element, it readily rises towards the Earth’s surface, where it either gets trapped under impermeable rock layers or leaks up to the surface. It is these leaks of natural H₂ that we are trying to trace in Mpumalanga for this part of the HyAfrica project.”

Prof Bumby added that environmentalists and climate change activists will also be interested in the potential impact of the development of natural H₂ as a commodity in South Africa.

“In other areas where H₂ has been exploited in the past, the extraction of natural H₂ typically requires drilling a borehole, and a motor engine adapted to run on H₂,” he said. “No further invasive procedures are envisioned. Burning H₂ in engines does not produce any carbon dioxide, or any other greenhouse gas, that contributes to global warming. The only combustion product is water. If the H₂ is not exploited, it seeps from the Earth into the atmosphere, reacts with oxygen and still forms water.”

The project was tasked with looking for sources of natural H₂ in Africa and exploring the possibility of using natural H₂ for stand-alone renewable energy solutions. The partners fall under the umbrella of LEAP-RE (Long-term Joint EU-AU Research and Innovation Partnership on Renewable Energy). The AU partners are in Morocco, Togo, South Africa and Mozambique.