Methodology — Quotas per BImSchG §37a(4) (BGBl. 2026 I Nr. 163). Multiplier per § 3 Abs. 5 37. BImSchV: 3.0 through 2036 → 2.5 / 2.0 / 1.5 / 1.0 (2037–2040+). Basiswert 94.1 gCO₂/MJ through 2025 and 94.0 from 2026 (§ 3 38. BImSchV as amended by BGBl. 2026 I Nr. 163); the reduction slider derives a product CI from the 94 g comparator a saving is measured against — § 10 Abs. 1 und 2 der 37. BImSchV with Part A of Delegated Regulation (EU) 2023/1185, the same figure as Annex V Part C point 19 of RED II. SMR reference: 0.048 MWh of gas per kg H₂ — a stated process assumption, equal to 69 % conversion onto the heating value, not a legal value — times 0.202 tCO₂/MWh, which is a legal default: natural gas carries 56.1 tCO₂/TJ of net calorific value in Annex VI Table 1 of the Monitoring and Reporting Regulation (EU) 2018/2066 (IPCC 2006 GL), and 56.1 × 0.0036 = 0.202. The two give 9.7 kg CO₂ per kg H₂ at the reformer — the stack term, with no upstream methane in it. Transmission: tariff € / kW / a × 39.4 kWh/kg HHV / load factor. Methanol mode: outputs in €/t (1 t = 1,000 kg); transport is commercial freight, not a network tariff; fossil anchor either quoted (EUA embedded) or derived as gas × 9.4 MWh/t (≈34 GJ) + EUA × 0.5 tCO₂/t + conversion margin — the cost floor of a European gas-based plant, while the traded price is import parity. Methane mode: outputs in €/MWh (50 MJ/kg LHV, 1 kg = 1/72 MWh); counterfactual is natural gas + EUA at 2.75 kgCO₂/kg (stoichiometric, assumes RFNBO zero-rating in the buyer’s ETS balance); the deduction is a grid & balancing fee per MWh. Credit formulas: Intermediate (additive) = mult × E × (FFC × (1 − Q %) − actual CI); Direct fuel (substitution) = mult × E × (FFC × (1 − Q %) − actual CI) + E × FFC × Q % — the displaced fossil litre leaves the reference basis, so the duty rises only by (mult − 1) × E — only where a fossil litre is displaced; for an intermediate, for electricity and for methane both bases coincide and the switch is inert; Reported = mult × E × (FFC − actual CI) per § 37a Abs. 4 S. 1 und 3 BImSchG (declared under § 37c Abs. 1) — the figure that goes on the report, and the one a naive price-indexation clause grabs. It is not offered as a saving basis above, because it is a marginal willingness to pay under neither route: the intermediate case nets to the additive basis and the direct-fuel case to the substitution basis, which meets the reported figure exactly from 2040 (multiplier 1); before that it overstates the intermediate case by ~40 % in 2030 and ~3.6× in 2040 at 90 % reduction. Contract logic: yearly WtP is levelized at Offtaker WACC to P_flat. With escalation e, P₀ is set so that the escalating stream's NPV at Offtaker WACC equals the yearly WtP NPV (offtaker indifference). Producer LCOH discounts that contract stream at Producer WACC. Who is obligated: § 37a Abs. 1 BImSchG obliges whoever places energy-tax-liable petrol or diesel on the market; the fuel counts as placed when the energy tax arises (Abs. 1 Satz 2), and the obligated party is the Steuerschuldner under the Energiesteuergesetz, or the Einlagerer in the cases of § 7 Abs. 4 EnergieStG (Abs. 3). A refinery is therefore obligated for the fuel it releases for consumption as tax debtor, not for what it produces; producing fuel with RFNBO hydrogen as an intermediate (§ 37a Abs. 5 Satz 1 Nr. 6 and 7) is a fulfilment option whose tonnes belong to whoever places that fuel — at an integrated company both roles coincide, at a merchant refinery they are two contracts. Low-carbon hydrogen: the one provision that names it, § 37a Abs. 5 Satz 1 Nr. 8 BImSchG, admits electrolytic low-carbon H₂ from obligation year 2031, only as an intermediate in the production of conventional fuels, and only once an ordinance under § 37d Abs. 2 Satz 1 Nr. 13 allows it — the 37. and 38. BImSchV (June 2026) contain no such provision, so it is not an option here.