Green Hydrogen (GH2)
GH2: a strong contender to replace fossil fuel
"The simplest and most powerful molecule"
Hydrogen, the most abundant element in the universe, forms the hydrogen gas (H2: molecular hydrogen) with the highest energy/weight ratio. In a world ruled by fossil fuels (oil & gas), it can be positioned as the "new" natural gas (NG) [EFI, 2022].
H2 is known for its versatility i) in coupling sectors (energy, mobility, industry, heating), ii) for serving economic niches difficult to electrify (as they require high energy densities), and iii) for scalable seasonal storage, an attribute not contemplated in other forms of energy storage, such as Li-ion batteries.
Green hydrogen (GH2)
Much attention has been paid for its potential role in combating climate change. Green hydrogen (GH2), the one produced w/o or w/ low carbon emission (discussions of "how low" can go on...), can clean up the i) agribusiness chain with the production of nitrogen fertilizers from green ammonia (via Haber-Bosch process), ii) mining sector, with the decarbonization of its operations (by replacing diesel oil) and the production of green explosives (from green ammonia), iii) steel sector, with the production of green pig iron (H2 acting as fuel & reducing agent), and iv) cement industry (acting as fuel in high-speed furnaces).
- From fossil fuels
Hydrogen is a synthetic energy carrier. Not existing in nature in its pure state, H2 is produced from fossil fuels (96% of the global H2 production at the end of 2021) by i) steam reforming of NG (most used today) and other light hydrocarbons (47% of the total H2 production), ii) partial oxidation of heavier hydrocarbons (refinery residues), and iii) coal gasification [DJ, 2023].
- From renewables
Sustainable H2 production, i.e., green hydrogen (GH2), is obtained i) by splitting water by electrolysis (4% of the total H2 production) or ii) by steam reforming, if bio-based feedstock is available [LINDE, 2023]. Electricity & CAPEX represent the greatest opportunities to reduce the total cost of GH2 production via electrolysis. Regarding to steam reforming tech, GH2 can be produced from biogas (60% CH4 + 40% CO2) as a renewable resource using a multistep process, including mainly i) biogas reforming, ii) water-gas-shift reaction, and iii) hydrogen separation.
- From renewables - SCW tech
Alternatively, a promising tech based on supercritical water (SCW), under development at Chemical Institute/UFG, allows the decentralized GH2 production from residual liquid biomass, agroindustrial effluents, and even urban residential sewage - low cost & high availability raw materials (related ref.: [JEQE, 2021]). Currently, 50-65% of the gaseous product from the gasification of liquid waste by SCW tech (operating at 22 MPa / 374 °C) is H2, a fraction that can be separated and purified to values greater than 99% w/ the addition of membranes or adsorption systems. As the SCW gasification reactor can be integrated w/ renewable primary sources, e.g., solar, OPEX and consequently LCOE is greatly reduced. SCW gasification of biomass has advantages over already established routes for H2 production, such as biogas reform: direct conversion of organic waste into H2 w/o the need for intermediate steps to remove contaminants and H2S, portability (mobility), and installation in small areas.
- From renewables - SPEG tech
In addition, Solena Plasma Enhanced Gasification (SPEG), a disruptive tech developed by SGH2 Energy, produces GH2 from any kind of waste, including paper, plastics, tires, and textiles. It uses a plasma-enhanced thermal catalytic conversion process optimized w/ oxygen-enriched gas (reaching 4000 °C) that disintegrates waste feedstock into its molecular compounds, w/o combustion ash or toxic fly ash. The HQ syngas produced, w/o byproducts produced by other gasification companies, goes through a PSA system resulting in H2 at "six nines" purity [SGH2, 2023]. Production costs are projected to be USD 2/kg,
From the other side of the system, fuel cells generate electricity through the oxidation of H2 (oxygen is obtained from the air), powering electric cars/machines and producing water vapor as a byproduct. In this conversion, about 50% of energy is lost. Other downside of hydrogen fuel cells is the high cost of the (critical) materials (e.g., Platinum, Iridium, Palladium) used to produce the catalysts, raising the upfront cost of energy cells (and also of water electrolysis systems).
H2 can also be burned in furnaces to generate heat or in internal combustion engines (ICE) for mobility applications, producing energy, water vapor, and NOx (nitrogen oxides), therefore not being classified as a zero-emission process, but pollutant of atmospheric air.
For large-scale storage of renewable energy, hydrogen is the most suitable alternative. Nevertheless, H2 storage emerges as obstacle to establishing the infrastructure for hydrogen tech, having become one of the key research areas in the H2 topic.
Many questions, few answers
Figure 1 summarizes the hydrogen supply chain, highlighting H2 producing rainbow (disruptive green tech approaches SCW & SPEG not shown), and end use. Within this figure, WoodMac reveals two of the most important questions related to the H2 paradigm, namely:
1. How competitive will each type (color) of H2 be?
2. What will future supply chains look like and what are the economics (*)?
(*) a composition between asset level economics & country level economics
Unfortunately, the answers are not straightforward. But we already have some (solid) bets, such as the one from Bloomberg, which states that the long-term goal for H2 to become a viable fuel is for it to cost 1-USD 2/kg, far from the current cost of GH2, USD 3-5/kg [BNEF, 2022].
The only certainty is that there's no turning back: many countries have already deployed hydrogen strategies, roadmaps and/or preliminary guidelines, as can be seen in the rightmost column of this table. South America is preparing its strategy to decarbonize hard-to-abate sectors by taking advantage of its locational attributes (find details here). For content in Portuguese related to this topic, please click here.
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Figure 1: Hydrogen supply chain, H2 rainbow & end use