China as Implementation Site for Solid-Phase Carbon Sequestration: Desert PV, Process Emissions, and Pacific Trench Access

This paper evaluates China as an implementation site for the solid-phase carbon sequestration pathway described in Prosch (2026): CO₂ capture → electrochemical conversion to solid carbon (MSCC-EC) → compaction into dense blocks → permanent deposition in ultra-deep ocean trenches. China uniquely combines three prerequisites: the world’s largest CO₂ emissions (~12 Gt CO₂/yr), vast desert areas with high solar potential (>1.5 million km²), and maritime access to five Pacific trenches exceeding 6,000 m depth within 800–2,100 nautical miles. A sensitivity analysis across three energy scenarios (SEC ×1/×2/×3) shows that PV area requirements for 1 Gt CO₂/yr CDR range from 99,000 to 276,000 km² of Chinese desert — 7–18% of available area. The analysis identifies China’s ~1.1–1.2 Gt CO₂/yr of unavoidable industrial process emissions (cement calcination, steel reduction, lime decomposition) as an immediate Phase-1 feedstock for point-source capture, with geological CCS as the technology-ready downstream default and solid-phase deposition as a long-term upgrade path. Two deployment models are presented: an organic baseline (conventional R&D trajectory) and a strategic mobilisation scenario that leverages China’s ongoing construction sector crisis as an infrastructure catalyst. Critical open problems are identified: MSCC-EC remains at TRL 2–3 with indeterminate scale-up timeline; the permanence argument is validated only for crystalline graphite, not for the actual MSCC-EC product spectrum (amorphous carbon, CNT, graphene); and regulatory barriers under the London Protocol are high to prohibitive.