Green hydrogen offers numerous potential applications Bernat Armangue/Associated Press/Alamy
Hydrogen, the most prevalent element in the universe, generates energy when it reacts with oxygen, producing only water as a by-product. This is why it is being hailed by politicians as a versatile solution to combat climate change, potentially powering the multitude of vehicles and industries that currently depend on fossil fuels.
However, 99% of the hydrogen in circulation today is “gray” hydrogen, derived from processes that decompose methane or coal gas, subsequently releasing carbon dioxide. To attain net-zero emissions, many nations are now pivoting towards “blue” hydrogen, which captures this CO2 before releasing it into the atmosphere, or “green” hydrogen, generated by using renewable energy to split water molecules.
UN Secretary-General António Guterres has remarked that green hydrogen represents a significant opportunity for Western nations to contend with China in the clean technology sector This was articulated at a press briefing on December 3rd.
The challenge is that low-carbon hydrogen costs at least double that of gray hydrogen. To boost production and reduce prices, government incentives are essential. While the European Union and others are backing the sector, former President Donald Trump has begun to dismantle proposed low-carbon hydrogen initiatives. This effort is ongoing in the US via a $7 billion initiative.
As a result of these obstacles, the analytics company BloombergNEF has revised its prediction for low-carbon hydrogen production down to just 5.5 million tonnes by 2030, amounting to around 5% of current gray hydrogen usage. Experts suggest that, given the limited availability of supplies, governments and organizations ought to concentrate on utilizing clean hydrogen where it is most beneficial for both the environment and the economy.
“Hydrogen can do nearly everything, but that doesn’t mean it should,” states Russell McKenna from ETH Zurich, Switzerland.
Recent studies conducted by McKenna and his team evaluated the CO2 emissions associated with producing and transporting low-carbon hydrogen for projects globally in 2000, contrasting it with the CO2 emissions this hydrogen could displace. Their findings indicate that hydrogen could significantly impact the climate in the manufacturing of steel, biofuels, and ammonia.
Conversely, employing hydrogen for road transport, electricity generation, and home heating sees limited emissions reductions.
Steel
In a blast furnace, coke made from coal serves the dual purpose of generating heat to melt iron oxide ore and supplying the carbon needed for chemical reactions that remove oxygen from the ore. Therefore, merely heating the metal using renewable electricity is insufficient. The reaction requires a carbon alternative, and hydrogen can produce water instead of CO2.
“The current technology allows for the production of iron from iron ore at an industrial scale without CO2 emissions, and that technology is hydrogen,” asserts David Dye from Imperial College London. “Any alternative would require substantial advancements in technology.”
Green steel startup Stegra is in the process of establishing a facility in northern Sweden, which aims to be the first carbon-neutral steel factory by the end of 2026, utilizing electric furnaces and green hydrogen generated from local river water. Similar projects are also being developed in Europe, Asia, and North America.
Nevertheless, generating green hydrogen and powering arc furnaces demands affordable renewable electricity. This year, the multinational steel producer ArcelorMittal declined a €1.3 billion subsidy aimed at transitioning two German steel mills to hydrogen, citing elevated electricity costs.
Ammonia
Crops require nitrogen in the form of nitrates to thrive, yet the soil contains limited nitrates. In the early 20th century, chemists Fritz Haber and Carl Bosch created a process that combines nitrogen, abundantly available in the air, with hydrogen to synthesize ammonia, which can then be transformed into various fertilizers.
This innovation fueled the agricultural revolution and the expansion of the global population, and today, hydrogen is primarily utilized in oil refining and ammonia production. Approximately 70% of all ammonia is used as fertilizer, while the remainder is employed in producing plastics, explosives, and other chemicals.
“You can’t electrify this… because it’s a chemical reaction requiring that input,” explains McKenna. “Thus, we need hydrogen, but it has to be decarbonized.”
Countries like Saudi Arabia are beginning to construct facilities that will leverage solar and wind energy to produce hundreds of thousands of tons of green ammonia, primarily for export. Simultaneously, a startup is working on compact, modular plants to generate green hydrogen and ammonia directly at US agricultural sites. However, at present, all these methods depend on governmental funding and tax incentives.
Alternative Fuel
Ammonia can also be burned in engines. While passenger vehicles and many trucks can efficiently operate on electricity, long-range transport methods, such as large trucks, ships, and airplanes, face challenges with battery storage and charging. Hydrogen holds potential as a key element in generating low-carbon fuels for this segment.
Research led by McKenna and his team has identified that manufacturing hydrotreated vegetable oils is one of the most advantageous applications of hydrogen. This involves treating used cooking oil with hydrogen to break down fats into combustible hydrocarbons.
Both ammonia and hydrotreated vegetable oil are being explored as substitutes for marine heavy fuel oil, which contributes to 3% of global emissions. The aviation sector, with a comparable carbon footprint, may also transition to ammonia.
Since hydrogen is produced independently of oil and closely resembles kerosene, it could also be harnessed to create synthetic aviation fuel compatible with existing aircraft.
In the long term, research teams at institutions like Cranfield University in the UK are conceptualizing aircraft featuring powerful tanks designed to store compressed hydrogen. Hydrogen and ammonia, which generate nitrogen oxide pollution when combusted, could alternatively be combined with oxygen in fuel cells, resulting in electricity and water. Ultimately, a fuel cell-powered aircraft represents a significant objective. Phil Longhurst from Cranfield University remarks.
“Hydrogen is the cleanest, zero-carbon fuel accessible, so it’s essentially the holy grail,” he concludes.
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Source: www.newscientist.com
