Hydrogen production is vital for its deployment. Co-produced industrial hydrogen is also called fatal hydrogen. What is behind this term? What is the issue with this source of hydrogen? How does this fit into a territorial project?
These are questions that we will try to answer through this article produced in partnership with the consulting firm EnerKa.
The hydrogen sector is changing. Between proven technical demonstrators and deployment projects aimed at economic viability, the question of the means of producing hydrogen is central. Compared to other energy vectors such as electricity or methane, hydrogen has a specificity which places it in an advantageous position.
Production of fatal hydrogen
We must first distinguish between voluntarily produced hydrogen (so-called “captive” or “merchant” hydrogen) and hydrogen resulting from a process not intended for its production (so-called “co-produced” hydrogen). The latter is generally either reused in other processes (sometimes even resold), or burned or stale (discarded into the open air). In industry, we will also distinguish the use of hydrogen for its physicochemical properties (excluding energy), which we will qualify as material hydrogen (production of nitrogen fertilizers for example), from the hydrogen used for its energetic properties, which we will qualify as hydrogen energy (heat production for example). Note that the energy uses of hydrogen are more easily substitutable than the material uses. Indeed, heat can be produced with natural gas or biomass while the production of fertilizer can only be done with hydrogen.
Sources and valorization of co-produced hydrogen
Today, hydrogen consumption in France is based on the oil refining, fertilizer production, chemical and metallurgy industries. However, more than half of these 900,000 tonnes of hydrogen consumed annually is of co-produced origin. Indeed, several industries in France are heavy producers of hydrogen without the latter being the product sought by their production process. For example, the chlorine industry carries out the electrolysis of brine to obtain the desired product (chlorine), but at the same time generates large quantities of hydrogen due to the nature of the reaction. Thus, this production represents 51,000 tonnes of hydrogen per year, or 6% of national production. In the same way, we can cite the processes of producing coke and refining petroleum products which represent respectively 14% and 40% of national hydrogen production.
Sometimes, the co-produced hydrogen is used as material hydrogen within the process itself (refinery for example) or in neighboring industrial processes (production of hydrogen peroxide). Regarding the valorization of hydrogen for its specific physico-chemical properties (matter hydrogen), the commercial value of this use is strong and hardly justifies a reorientation of this hydrogen in mobility. On the other hand, hydrogen co-produces is sometimes recovered in the form of heat (to produce water vapor), or even released into the open air, because there are no other economically interesting outlets nearby. In this scenario, hydrogen does not have a high economic value, because other raw materials can replace it, such as natural gas. This configuration makes the use of this co-produced hydrogen in mobility more relevant, because the manufacturer will derive more value from it. The co-produced hydrogen, thus recovered in the form of heat, represented 237,000 t/year in 2008 (1) or 650 t of hydrogen per day (mainly from the production of chlorine and coke). As a reminder, a private vehicle consumes around 1 kg/100 km, a bus 10 kg/100 km and a fleet of 50 buses around 1 t/day. The development of this potential would therefore correspond to the consumption of more than 30,000 hydrogen buses, the equivalent of the French bus fleet.
Challenges for mobility
To fully understand the interest that co-produced hydrogen represents for territorial hydrogen mobility ecosystems (production, distribution, uses), it must be emphasized that the latter must today decide on the way of producing hydrogen. Indeed, electrolysis is often highlighted for its low carbon impact, but its price still remains high and requires producing large quantities of hydrogen with low-cost electricity to achieve fuel price parity with diesel. In contrast, the reforming of natural gas allows a competitive price for hydrogen, but only makes a moderate contribution to the climate issue. The valorization of hydrogen co-produced in these territorial mobility ecosystems therefore makes it possible to reconcile these two visions, environmental and economic. Since the co-produced hydrogen used for heat (or even released into the air) has only a low commercial value, the latter can be sold at the end of the process at a very competitive price, less than €3/kg (2), or even zero. For comparison, depending on the assumptions, hydrogen fuel reaches a price equivalent to diesel between 6 and 9 €/kg (3). However, these promising figures should not overshadow the investments necessary for separation, purification, packaging (compression, storage), transport and distribution, all necessary to transport quality hydrogen to the tank of a vehicle. However, the economic equation remains very interesting and competitive compared to diesel (4). Beyond investment and operating cost considerations, the recovery of “waste” is part of the circular economy. Thus, the economic benefits go beyond the classic advantages of hydrogen (air pollution control, global warming, energy balance), because they directly benefit the region’s industrial sector by providing a new source of income. Conversely, the overall economic situation, and therefore the volume of activity of the manufacturer, will influence the volume of co-produced hydrogen given that the latter is directly linked to the production of a commercial product. A global economic crisis reducing global chlorine consumption will de facto have an impact on the quantity of co-produced hydrogen available.
The environmental aspect
The carbon intensity of this hydrogen will depend on the industrial process from which it comes. In the case of chlorine production, this involves electrolysis of the brine and therefore electricity consumption. In France, with a low-carbon electricity mix, the co-production of hydrogen therefore emits very little CO with less than 1 kg of CO per kilo of hydrogen, or 10 times less than the reforming of natural gas. Co-produced hydrogen from coke ovens will have a much higher carbon component given that it comes from fossil fuels such as coal. The question is whether it is relevant to attribute all of the CO emissions from a coke plant to hydrogen, which is not the product targeted by the main production process. The method commonly used in life cycle analyzes to answer this question is commercial value arbitrage. In the case of the coke plant, if revenues linked to the sale of coke represent 95% of the turnover of the coke plant and those linked to the sale of hydrogen 5%, then hydrogen will have a carbon footprint equal to 5 % of CO emissions from the coking plant. Following this reasoning for coke ovens or in the case of chlorine production, the co-produced hydrogen therefore has a relatively low carbon component compared to other hydrogen production processes. Finally, an important point should be highlighted in the case where the co-produced hydrogen is initially recovered in the form of heat. Indeed, even if hydrogen is redirected towards use in mobility, the industrial heat needs remain unchanged. The latter will therefore have to purchase and consume an additional quantity of natural gas (in the case of a gas boiler) in order to compensate for the absence of hydrogen energy now used in mobility. In life cycle analysis, this so-called substitution consequence must be taken into account in the calculation of the CO impact. The CO impact of this substitution still remains lower than the production of hydrogen by reforming natural gas.
Territorial projects
Thus, the valorization of co-produced hydrogen is a major challenge for hydrogen mobility in France for the reasons mentioned above. Since co-produced hydrogen is linked to a given industrial site, this is a potential with strong local roots. Projects such as Valhydate (South Provence-Alpes – Côte d’Azur region) or Vhyctor (Bourgogne-Franche-Comté) have understood this well and thus aim to demonstrate its economic and environmental relevance. As industrial sites are located on the outskirts of urban areas, strong synergies can be found with bus depots which are sometimes located a few hundred meters from these installations. Powering freight trains, or even passenger trains, passing near these sites is another example of synergy justifying this type of project. Finally, industrial sites are also logistics nodes for the supply of raw materials and the export of products. This configuration induces constant comings and goings of trucks, even boats, the latter of which can also be powered by hydrogen co-produced on the industrial site. Once developed around a particular site, all of these uses will mechanically radiate out to the rest of the territory and thus justify the establishment of other stations with other means of production, this quickly making it possible to initiate a territorial hydrogen ecosystem. The entire French potential is not yet exploited and that local elected officials in the targeted territories have an important card to play in the development of competitive hydrogen mobility. The strong potential of co-produced hydrogen highlighted in this article should not overturn the priorities of a hydrogen project. Indeed, identifying the uses of hydrogen, raising awareness and canvassing future vehicle users remains the basis of any territorial project. It is not the presence of a station and competitive hydrogen that will spontaneously bring users in! Co-produced hydrogen therefore presents itself as an initiator of short-term territorial dynamics, especially since some of these deposits have not yet been exploited. Although they are significant today, the limited quantities of co-produced hydrogen do not overshadow other hydrogen production processes which are complementary depending on the resources of a territory (electrolysis in the presence of solar or wind power, pyrogasification in the presence of biomass resources, etc.).
Notes
(1) Alain Le Duigou and Marianne Miguet, “The French industrial hydrogen markets: situation in 2008 and outlook”, L’Actualité Chimique, n° 347, p. 52–57.
(2) Energy equivalent at the price of natural gas.
(3) Depending on the price of diesel and the fuel efficiency of the engine.
(4) Source EnerKa.