7.3. Technologies for Hydrogen Production

Technologies for hydrogen (H₂) production fall into four main categories:

Thermal Processes: Thermal processes use the energy in various feedstocks (natural gas, coal, biomass, etc.) to release the H₂ that is part of their molecular structure. The main hydrogen production technologies using fossil fuels are all thermal processes, and include reforming, gasification, and pyrolysis. Table 1 summarizes fossil fuel-based hydrogen production technologies.
Biological & Thermochemical Processes: Thermochemical processes use heat in combination with a closed chemical cycle to produce H₂, while biological processes use microbes or fungi in fermentive reactions to produce gases from which hydrogen can be derived.
Electrolytic Processes: These processes use electricity to split water into its two chemical constituents, oxygen (O₂) and H₂, using an electrolyzer. The cost and efficiency of producing H₂via electrolytic processes is directly dependent on the cost and efficiency of the electricity used in the process.
Photolytic Processes: These processes use light energy to split water into H₂ and O₂. These processes are currently in the early stages of development and currently are not viable for large scale production.

Table 1: Fossil fuel-based hydrogen production technologies¹

Technology		Feedstock	Operating Conditions	Maturity
Reforming Technologies	Steam Reforming	Light hydrocarbons (less frequently from liquefied petroleum gas and naphtha)	900-1000 ℃	Commercial
	Partial Oxidation	Hydrocarbons, heavy fuel oil, and coal	Temperature of > 1000 ℃	Commercial
	Autothermal Reforming	Light hydrocarbons (less frequently from liquified petroleum gas and naphtha)	Temperature of > 1000 ℃	Early Commercial
Pyrolysis		Hydrocarbons	500-800 ℃ in the absence of oxygen	Commercial
Gasification		Coal	700-1200 ℃	Commercial

NETL recently produced a baseline study which independently and transparently evaluated the performance of select hydrogen production plants utilizing fossil fuel resources as the primary feedstocks – specifically, natural gas, steam methane reforming, autothermal reforming of natural gas, coal gasification, and coal/biomass co-gasification. The cases assumed commercially available technologies and included both non-CO₂ capture and capture cases to gauge the performance and cost implications of clean hydrogen production using these technologies; the cases are summarized in Table 2. For details on process configurations, assumptions, and cost contributors/breakdowns, refer to the original baseline study here. Nominal CO₂ capture rates vary, but for the capture cases (2, 3, 5 and 6) there is a consistent strategy to recover greater than 90 percent of the carbon entering the plant boundary, minus the slag formed in gasification cases.

Table 2: NETL Fossil Fuel-based Hydrogen Plant Cases

Case	Plant Type	Feedstock	Technology Type	CO₂ Capture (%)	Hydrogen Production Capacity	Levelized Cost of Hydrogen
1	Reforming	Natural Gas	Steam Methane Reforming	0	483,000 kg/day	$1.06/kg
2			Steam Methane Reforming	96.2	483,000 kg/day	$1.54/kg
3			Autothermal Reforming	94.5	660,000 kg/day	$1.51/kg
4	Gasification	Illinois No. 6 Coal	Shell/Air Products-type oxygen-blown, entrained flow gasification	0		$2.58/kg
5		Illinois No. 6 Coal		92.5		$2.92/kg
6		Illinois No. 6 Coal/ Torrefied Woody Biomass		92.6	133,000 kg/day	$3.44/kg

It is interesting to note that the inherently carbon capture-facilitating autothermal reforming has slightly better cost performance compared to steam methane reforming when the latter is forced to include carbon capture. Cost contributors are discussed in detail in the source document, but it can be noted here that the largest contributor to the cost of hydrogen for reforming cases is the fuel cost, in contrast to the gasification cases where capital cost is the largest contributor.

More detail on the gasification-based plant cases (Cases 4-6) is provided in subsequent sections of this chapter below, showing current technological & process approaches to gasification-based hydrogen production systems with and without carbon capture.

Table 3 compares technologies for production of hydrogen using water and biomass feedstocks; most of these technologies are biological, thermochemical, electrolytic, or photolytic, though thermal conversion of biomass via gasification and pyrolysis is well established. Some of the technologies such as thermolysis, photoelectrolysis and biophotolysis are in the research and development (R&D) stage and will require years of improvements before becoming a commercial reality.

Table 3: Non fossil-fuel based hydrogen production technologies¹

Technology		Advantages	Drawbacks	Energy Efficiency (%)	H₂ yield (g/kg_feedstock)	Cost ($/kg of H₂
Water	electrolysis	simplicity low temperatures zero carbon emissions O₂ as a byproduct integration with fuel cells	high pressure is required energy storage problems low system efficiencies high capital costs	55−80	111^α	4.15−10.30
	thermolysis	clean and sustainable zero carbon emissions O₂ as a byproduct	separation step is required to avoid the recombination in an explosive mixture high capital costs	20−50	111^α	7.98−8.40
	photoelectrolysis	contributes to the sustainability of the energy supply photonic and electrical energies can be converted to chemical energy low operating temperature and pressure	low efficiency requires a significant surface photocatalytic material is required	0.06−14	111^α	4.98−10.36
	biophotolysis	can produce hydrogen at ambient conditions consumes CO₂	requires a significant surface area to collect enough sunlight difficult operations to control the different bacteria large reactor volume	10−15	111^α	1.42-2.13
Biomass	dark fermentation	can produce hydrogen at any time because light is not required ambient conditions simple reactor design waste recycling	hydrogen yield is metabolically restricted high byproduct generation low efficiency large reactor volume	60−80	4-44	1.68−2.57
	photofermentation	allows for hydrogen production from a wide range of substrates, including waste streams high removal efficiency of the chemical oxygen demand waste recycling	strict control of environmental conditions is required requires a significant surface area to collect enough sunlight nitrogenase metabolism restricts economic viability of hydrogen production large reactor volume	0.1−12	9-49	2.57-2.83
	pyrolysis	developed technology abundant and cheap feedstock solid, liquid, and gas product streams carbon-neutral emissions	hydrogen yield depends upon the feedstock tar formation	35−50	25-65	1.59−2.20
	gasification	abundant and cheap feedstocks carbon-neutral emissions	requires oxidation agents hydrogen yield depends upon the feedstock tar formation	30−60	40-190	1.77-2.05
	hydrothermal liquefaction	abundant and cheap feedstocks drying step is not required high energy efficiency solid, liquid, and gas product streams	hydrogen yield depends upon the feedstock presence of nitrogenated compounds	85−90	0.3-2	0.54−1.26
	steam reforming	developed technology avoid the costly upgrading of the bio-oil	produce carbon co-products	74−85	40-130	1.83−2.35

^αCalculated from the water-splitting reaction stoichiometry.

Cost of Hydrogen Production

The cost of H₂ hydrogen production depends heavily on the cost of fuel or electricity from which it is produced, and in the case of clean hydrogen, carbon capture and storage costs must factor into the equation for non-renewable production methods. In the Global Hydrogen Review of 2021, the International Energy Agency surveyed recent (2020) hydrogen production costs via the major methods including natural gas reforming (without and with carbon capture and storage [CCUS]), coal gasification (with and without CCUS), and renewables, and compared those costs with expected future costs in net zero emissions scenarios for 2030 and 2050. Those are shown in Figure 1. Currently, hydrogen produced via all reforming and gasification methods with and without capture is less expensive than renewable hydrogen, but with future carbon price liabilities factored in and expected future cost reductions of renewable technologies, fossil fuel with capture and renewable technologies may be on a more even cost footing. Notably, solid fuel/coal gasification with capture may remain a strong contender in anticipated future net-zero emissions scenarios.

7-3 Figure 1 — **Figure 1. Levelized cost of hydrogen production by technology in 2020, and in the Net zero Emissions Scenario, 2030 and 2050²**

References/Further Reading

“Hydrogen Production Technologies: From Fossil Fuels toward Renewable Sources. A Mini Review,” Pedro J. Megía, Arturo J. Vizcaíno, José A. Calles, and Alicia Carrero, Energy & Fuels 2021 35 (20), 16403-16415 DOI: 10.1021/acs.energyfuels.1c02501
Global Hydrogen Review 2021, International Energy Agency. https://iea.blob.core.windows.net/assets/5bd46d7b-906a-4429-abda-e9c507a62341/GlobalHydrogenReview2021.pdf

Comparison of Commercial, State-of-the-art, Fossil-based Hydrogen Production Technologies, National Energy Technology Laboratory, April 12, 2022 DOE/NETL-2022/3241.Hydrogen: Automotive Fuel of the Future, by FSEC's Ali T-Raissi and David Block, IEEE Power & Energy, Vol. 2, No. 6, page 43, Nov-Dec 2004
Hydrogen from Coal, D. Gray & G. Tomlinson, Mitretek Technical Paper (Nov 2001)

Hydrogen

Why Hydrogen
Hydrogen & Synthetic Natural Gas from Gasification
Technologies for Hydrogen Production
- Gasification-Based Hydrogen Production without Carbon Capture
- Gasification-Based Hydrogen Production with Carbon Capture
Technology for SNG Production
SNG from Coal: Process & Commercialization
DOE Supported R&D for Production of Hydrogen