Hydrogen is an environment and climate-friendly (zero-emission) energy carrier. Produced from renewable energy sources (RES), e.g. sun and wind energy, hydrogen has significant potential to completely replace fossil-based energy and thereby avoid all the related CO2 emissions.

Green Hydrogen is hydrogen produced through electrolysis from renewble energy sources such as photovoltaic , on-shore and off-shore wind, hydroelectric plants or similar. Since neither the production of renewable energy nor the conversion to hydrogen create any CO2, green hydrogen is emission free and has zero GHG footprint.

Grey Hydrogen is produced from natural gas (=methan, CH4) through an industrial process called Steam Methane Reforming (SMR) . During this process, 10 kg CO2 is created for each 1 kg of hydrogen. When this CO2 is emitted into the air, the resulting hydrogen has a high GHG footprint. When at least 60% of this CO2 are captured and either used or stored (CCU/CCS) the resulting hydrogen is called blue hydrogen. Blue hydrogen has a lower GHG-footprint – 4kg CO2 per kg of hydrogen or less – than grey hydrogen, but it is more costly to produce. The bigger the share of CO2 removed, the higher the value for the climate, but the higher also the cost.

When hydrogen is produced from electricity other than renewables, the electricity entails CO2 emissions and the resulting hydrogen is then not CO2 emission free. The GHG-footprint resulting from using not renewable hydrogen depends on the electricity type. based on the average EU electricity ix, the emissions are 38,4 kgs of CO2 for each kg of hydrogen produced. For the ultimate goal of emission reductions it is important to use RES.

When producing hydrogen from biogas (usually also through SMR) there is no additional GHG-footprint since the CH4/CO2 would have been emitted to the atmosphere anyway.. So the contribution form the source of the input gas to the hydrogen production process is „net-zero“. There is however still emissions stemming from the production process so the resulting GHG footprint is ca. 2 kg of CO2 emissions for 1 kg of hydrogen produced through this method.

The below graph gives a comparison of the resulting GHG emissions The first bar in the chart is 0, it comes from green hydrogen



The cost of green hydrogen depends to an important extent on the cost of the renewable electricity used. The cost for Solar energy depends on the intensity of the sun. With the same size of PV installation it is possible to produce twice as many MWhs in Spain than in the north of Germany, because the sun shines longer and is more intense in Spain. The solar energy to be harvested in different parts of Europe is indicated in the graph by the color.


Hydrogen is a very light substance but it takes a lot of space and is difficult to compress (very high pressures needed) or to liquify (very low temperatures needed). This makes it difficult and costly to transport from the place where it is produced to the place where it is used. The cheapest option is by pipelines very similar to natural gas pipelines. Like for natural gas, these pipelines can go up to 120cm diameter and a pressure of 80 bar. The main difference to gas pipelines is the need for tightness, since hydrogen is very fugitive and will escapee’s through thinest cracks and leaks. The pipeline equipment is similar except for the compressors, which need a new technology to handle the specific characteristics of hydrogen.

Most Pipelines built in the recent 30 years will basically be fit for hydrogen, the only thing that needs to be replaced are the compressors. Such repurposing of spare natural gase pipelines provides a convenient way for transition from natural gas to hydrogen since it is very cost efficient and estimated to save 90% of the cost compared to new pipelines. Transporting green hydrogen in such repurposed pipelines is estimated to cost only 9-17 ct per kg per 1000 km. (see EU Hydrogen backbone study)


Grey hydrogen and green hydrogen (as well as all other colors) are the same substance. So they can be substituted without any technical changes. However, existing supply contracts cannot be canceled without notice, so there is a time delay. And the most important factor is of course the cost. Grey hydrogen is normally sold for 1,5-1,7 € in industrial quantities and delivered at the point of use. Such a price level is difficult to reach without significant cost reductions for the production of green hydrogen. Apart from cost reductions in green hydrogen production there are 2 developments helping to overcome this gap. On the one hand regulation is being prepared to make grey hydrogen production more expensive. The most obvious one is the removal of the exemption from the ETS system, which could be announced still in 2021. But also other CO2 charging systems and fees are being envisaged. On the other hand there could be subsidies to close the gap at least for the initial ramp up of green hydrogen. So the obstacles are commercial, no technical obstacles.


More than 100 hydrogen buses are in operation today and have already delivered more than 7 million „passenger kilometers“. More are being produced and put in service every week, The main obstacles here is the cost efficient supply of green hydrogen. The central bus depot is normally a good location to have a single point of hydrogen production, but cost of electricity can still be a significant obstacle, as well as the supply of non-fossil electricity. Also there is a certain size dependency : small busses (10-20 seaters) are usually better off to just run on batteries. For 18 meter buses in a hilly environment hydrogen is the only viable choice. For normal sized busses both options have their merit, but in any case there is a need for a massive increase in numbers of busses produced to get the production price down in order to reach a critical level for TCO.

Energy Sector

Indeed the reconversion of hydrogen into electricity results in a significant overall system loss. Nevertheless, hydrogen is still the most efficient long term storage of renewable electricity. And with renewable supply (from photovoltaics) being high in summer and energy demand being high in winter there is a fundamental need for seasonal energy storage. What is most important is the availability of energy when it is needed and the related costs. The (lack of) efficiency may be deplorable but it is secondary. And as long as the original energy is carbon free, there is also no negative impact on climate emissions. On the contrary : if extra fossil energy production in winter can be avoided by stored renewables, there is a positive impact on the climate

The basic issue here is the significant lack of renewable electricity when trying to replace all fossil forms of electricity. So the issue is, how to best use „additional“ renewable electricity to maximize the climate impact. And if it is looked upon at national level, there are many countries in the EU which will never be able to produce sufficient renewable energy to replace all fossil based energy. But there are countries who today already have an excess of renewables and have to shunt (=throw away) renewable electricity at peak times. This is called curtailment and Spain alone had curtailments of 9 TWh in 2018. So there is not only a „time of day“ issue when talking about converting to renewable energy supply but there is also a „season in the year“ issue and a „geographic location“ issue. In summary : The issue of „additionality“ is a real one in the context of maximizing the utilization of renewable electricity to fight climate change. But it cannot be solved by a simple no to all non-electrical uses. The issue behind the emotional discussion is the legal uncertainty created by the „additionality“ requirement in the Renewable Energy Directive of the EU. This legal uncertainty blocks the evolution of alternative sources of supply, in particular green hydrogen. That is why it should be resolved and clarified as soon as possible.


The main energy need in buildings is for heating and cooling purposes. And there again there is the discussion of efficiency. Converting electricity into heat is indeed more efficient than converting electricity first into hydrogen and then from hydrogen into heat. However, we have again the issue of seasonality. So when heat is most needed renewable electricity is least available. So energy stored in the form of hydrogen can well be the best solution. A further element in this discussion is district heating. Wherever hydrogen is used or converted into electricity, there is significant waste heat available. If this waste heat can be put into a district heating system, the efficiency of hydrogen is highly increased. Such a situation can easily arise in the context of a hydrogen Vally configuration. A similar but smaller scale case is CHP, where again production of heat and of electricity are combined locally, significantly reducing efficiency losses. So in some situations, using hydrogen for heating will be quite efficient.



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