When does methane pyrolysis become competitive? A life-cycle and total cost assessment of hydrogen pathways

Methane pyrolysis (MP) is increasingly discussed as a low-carbon hydrogen pathway, yet its life-cycle performance remains highly sensitive to methane conversion and carbon coproduct utilization. This study presents a harmonized cradle-to-gate life-cycle and cost comparison of MP with steam methane reforming (SMR), SMR with carbon capture and storage (SMR + CCS), and water electrolysis (WE). All pathways are evaluated using a consistent functional unit (1 kg H 2 at the plant gate, 200 bar) and integrated ReCiPe 2016 midpoint and monetized endpoint indicators to define the total cost of hydrogen (TCH). Results show that MP without carbon credit matches SMR only at near-complete conversion (100%, ∼12.6 kg CO 2 eq kg −1 H 2 ). With avoided-product credit for carbon black, MP approaches SMR + CCS (∼5.1 kg CO 2 eq kg −1 H 2 ) but loses advantage below ∼50–55% conversion. Median TCH values (USD 2024 kg −1 H 2 ) are 6.6 for SMR, 10.8 for MP, and 4.8 for MP with avoided-product credit, indicating that MP competitiveness requires high conversion efficiency, low-carbon electricity, and viable carbon markets. • Harmonized cradle-to-gate life cycle and cost comparison of hydrogen pathways. • Methane conversion thresholds determine the competitiveness of methane pyrolysis. • Carbon co-product credit strongly affects methane pyrolysis performance. • Total cost of hydrogen includes monetized environmental damage costs. • Competitiveness requires high conversion, low-carbon electricity, and carbon markets.