There is ongoing debate over whether sustainably produced hydrogen should be 100 percent green. Using ammonia and artificial fertilizer production as examples, researchers have calculated that “nearly sustainable” hydrogen would ultimately be preferable.
Hydrogen storage – illustrated photo. In April 2024, power company Expo opened a hydrogen production facility adjacent to a hydropower plant in the Swiss canton of Graubünden. A large-scale ammonia plant would require a very large facility. Image Credit: Expo Group
Sustainably produced hydrogen has a role to play in the energy transition, and not just as an energy storage medium or fuel for lorries. In industry, it can be used where hydrogen is already needed today: for example, in the production of ammonia. 180 million tons of ammonia are produced each year worldwide, mainly for the fertilizer industry. The required hydrogen is currently obtained from natural gas, resulting in high greenhouse gas emissions and dependence on gas exporting countries. Using green hydrogen as a clean alternative will bring the world closer to climate goals and reduce dependence. Green hydrogen is produced using sustainable electricity through a process called electrolysis.
In a study looking at the European ammonia industry, researchers at the Hong Kong University of Science and Technology (HKUST) and ETH Zurich have now calculated the conditions under which it would make sense to convert ammonia production to green or near-green hydrogen.
Already economically viable in Spain and Norway
Two results emerged. First of all, in some European countries such as Norway, Spain, Hungary or Poland, ammonia production from green or almost green hydrogen already makes economic sense today. In these countries, generating sustainable electricity from solar or wind power is particularly cost-effective. This can be attributed to the favorable geographical conditions of these countries, as well as state subsidies or generally low electricity costs. The latter means that, in the absence of sunshine or wind, hydrogen production can rely on cheap electricity from the grid. As a result, producers here can do without expensive storage solutions for sustainable electricity.
Second, even electricity that is not completely fossil-free will have an entirely positive impact on climate. According to the study, hydrogen obtained from electrolysis makes no sense even if some of the electricity used is not from renewable sources. This gives producers the freedom to switch to power from the grid, some of which comes from fossil sources, whenever sun or wind is in short supply.
one kilogram CO2 will be good for the climate
The lead author of the study is Stefano Mingola, a doctoral student at HKUST. He worked for six months in a group led by Professor Giovanni Sansavini of the Department of Mechanical and Process Engineering at ETH Zurich. “If you use almost green hydrogen to produce ammonia, you can achieve a lot very quickly – it’s low-risk,” Sansavini says. “This is in contrast to other applications, where hydrogen serves only as energy storage and requires conversion from one form of energy to another. In ammonia production, hydrogen is used directly as a raw material, eliminating the need for inefficient conversion.
Mingola and his colleagues’ calculations show that greenhouse gas emissions from ammonia production could be 95 percent lower than today if the hydrogen used is produced in such a way that no more than a kilogram of CO is released.2 per kilogram of hydrogen. The electricity required should be significantly greener than the current mix in Germany, Poland and the Netherlands. These three countries are the largest ammonia producers in Europe. For comparison: one kilogram of hydrogen produced using the Swiss electricity blend would emit 1.7 kilograms of CO2, Using the current electricity mix in Germany this figure would be 18 kg CO2216 kg in the Netherlands and 33 kg in Poland.
It would be extremely expensive to completely decarbonize hydrogen production instead of just 95 percent. The last 5 percent of decarbonization is the most complex and expensive; This will be almost double the total price. “It is important to adjust ambitions accordingly,” says Sansavini. “Aiming for complete decarbonization would be counterproductive, as excessive costs could slow down the energy transition.”
New solar and wind parks for hydrogen production
However, Sansavini emphasizes that hydrogen will not be produced on a large scale using electricity from the grid, because in many cases, both local power generation and cross-border grid transmission capacity are insufficient.
New solar or wind farms are more likely to be built right next to existing ammonia plants. However, this requires large areas of land. As studies show, the more favorable the geographical conditions are in an area to generate electricity from solar or wind energy, the less land is required. Southern Europe and areas along the Atlantic coast have an advantage here. “Since the amount of land required is so large, we need to think mainly about combined land use – for example, a wind or solar farm where farming can be done at the same time,” says Sansavini.
Green hydrogen may already be competitive in Norway, Spain, Hungary and Poland, but on average across Europe it is significantly more expensive to produce than extracting hydrogen from natural gas. “To make green hydrogen competitive everywhere, further investment in research and development is needed, as well as economic incentives,” Sansavini says. What “green” hydrogen actually means is also currently under discussion in the EU. “We need to balance cost and environmental impact. Any definition of green hydrogen must be allowed to include some residual fossil energy,” Sansavini explains. Using the example of ammonia production, the research team has now calculated a recommendation for this residual ratio: a Kilogram to CO2 Hydrogen emissions per kilogram would be acceptable and sensible.
Source: ETH Zurich
