Ways to make Hydrogen

3 routes in the Atlas, side by side per the same functional unit. Whether they compare is computed from their data, criterion by criterion; a warning sits next to each route it concerns.

Not comparable as they standAllocation: differs; Reference product (grade, state): differs. The rows say which route each warning concerns.

Per 1 kg of Hydrogen: inventory from each route's LCI dataset, unallocated; footprints per the functional unit of their own LCA.

Route	Tier, design maturity, review status	Geography, year	Energy	Feedstocks	Key emissions	Footprint	Comparability
Chlor-alkali by membrane-cell electrolysis (100 kt/a Cl2, 50 wt-% caustic soda, hydrogen)bipolar membrane-cell NaCl electrolysis, 100 kt/a Cl2, rock salt with brine recirculation, 3.0 V at 6.0 kA/m2, double-effect caustic evaporation to 50 wt-%	flowsheet or hand-writtenDesign maturity: Concept (research)Not independently reviewedDataset review: unreviewed	GLO, 2026	a co-product of a multi-output dataset (product:CL2, product:NAOH besides it): its share needs the allocation of the LCI database build			no footprint	Reference product (grade, state): product is no grade (basis mass, component H2, pressure 1.4, purity 0.6789415, temperature 64.04); the routes state no grade (basis mass, component H2, pressure 1.4, purity 0.6789415, temperature 64.04), no grade (basis mole, component H2, pressure 28.5, purity 0.998996, temperature 40.0), no grade (temperature 40.0) Allocation: allocation is shares; the routes state energy, exergy, shares
Toluene hydrodealkylation to benzene (100 kt/a, thermal HDA)thermal toluene hydrodealkylation, adiabatic reactor 895-936 K / 3.4 MPa, H2 recycle with purge and purge hydrogen recovery by PSA, stabiliser, benzene and vacuum toluene columns; 100 kt/a benzene, concept design	flowsheet or hand-writtenDesign maturity: Concept (research)Not independently reviewedDataset review: unreviewed	GLO, 2026	a co-product of a multi-output dataset (product:BENZENE, product:DIPHENYL besides it): its share needs the allocation of the LCI database build			no footprint	Reference product (grade, state): product is no grade (temperature 40.0); the routes state no grade (basis mass, component H2, pressure 1.4, purity 0.6789415, temperature 64.04), no grade (basis mole, component H2, pressure 28.5, purity 0.998996, temperature 40.0), no grade (temperature 40.0) Allocation: allocation is energy; the routes state energy, exergy, shares
Hydrogen by natural-gas steam methane reforming with PSA (100 000 Nm3/h, steam export)natural-gas steam methane reforming, top-fired tubular reformer, HT shift, hydrogen PSA, tail gas firing, steam export; 100 000 Nm3/h	flowsheet or hand-writtenDesign maturity: Concept (research)Not independently reviewedDataset review: unreviewed	generic, 2026	Electric power: 0.164 kWh	Natural gas feedstock: 3.23 kg Natural gas trim fuel: 0.619 kg Combustion air: 31 kg (free) Demineralised make-up water: 15.7 kg	C2H6 to the environment: 0 kg C3H8 to the environment: 0 kg CH4 to the environment: 0.0000869 kg CO to the environment: 0.00252 kg CO2 to the environment: 10.1 kg H2 to the environment: 0.00000714 kg H2O to the environment: 4.09 kg N2O to the environment (estimated): 0.00000869 kg NOx to the environment (estimated): 0.00643 kg	9.14 kg CO2-eqClimate change per 1 kg hydrogen	Reference product (grade, state): product is no grade (basis mole, component H2, pressure 28.5, purity 0.998996, temperature 40.0); the routes state no grade (basis mass, component H2, pressure 1.4, purity 0.6789415, temperature 64.04), no grade (basis mole, component H2, pressure 28.5, purity 0.998996, temperature 40.0), no grade (temperature 40.0) Allocation: allocation is exergy; the routes state energy, exergy, shares

How comparability is checked

Allocation: differs (same allocation method: energy, exergy, shares)
Background data (impacts): not applicable (same background data and boundary behind the impact numbers (only routes with a footprint))
System boundary: same (same system boundary of the inventory (the dataset's boundary): gate-to-gate foreground of the plant)
Data quality (TfS DQR): same (data quality: every route states a TfS DQR, none more than 1 above the best)
Functional unit: same (same functional unit (amount and unit of the reference product): 1 kg)
Reference product (grade, state): differs (same reference product: registry grade and state: no grade (basis mass, component H2, pressure 1.4, purity 0.6789415, temperature 64.04), no grade (basis mole, component H2, pressure 28.5, purity 0.998996, temperature 40.0), no grade (temperature 40.0))
System model: same (same system model (docs/system-model.md): cutoff)

ISO 14044 requires a critical review (by a panel of interested parties, ISO/TS 14071) of a comparative assertion intended to be disclosed to the public. These routes are listed side by side for screening; a statement that one is better than another needs that review. None of these routes has had such a review.