Yuezhang He

Green ammonia is taking center stage as a low-carbon marine fuel, driving the shipping sector’s net-zero transition. However, the ramifications of soaring demand for clean marine fuel on today’s carbon-intensive ammonia production and the spatiotemporal evolution of ammonia supply chains are far from clear. Here, we develop a technology-rich, multi-region model for China optimizing production routes, facility locations, and transportation under various policy and infrastructure scenarios. The results reveal that large-scale deployment of green hydrogen to ammonia could begin around 2030, cutting CO2 emissions by >90% by 2050, though supply costs will rise 6%–30% above 2020 levels. Pipelines could cut costs by 18% compared with trucks by improving supply-demand matching, and carbon prices above 100 USD/t CO2 are needed to make green ammonia viable as a marine fuel by 2060. Our findings offer a feasible green ammonia road map for China with strategic priorities for both policy and infrastructure development.

Addressing climate change requires decarbonizing the iron and steel industry, which accounts for about 7% of global CO2 emissions. Hydrogen-based direct reduced iron with electric arc furnaces (H2-DRI-EAF) emerges as a promising pathway, yet its economic viability hinges on effectively managing the variability of renewable energy. However, heterogeneous flexibility potentials across electricity, hydrogen, iron, and steel production, together with the distinct characteristics of intermediate product storage, make coordinated capacity investment highly complex. This study develops a system-level modeling framework for renewable-centric, multi-stage H2-DRI-EAF that jointly optimizes capacity sizing and flexible operations across production stages under flexibility strategies in representative Chinese steelmaking cities. We find that fully deploying flexibility across all production stages could reduce the levelized cost of steel (LCOS) by 6–10% relative to baseline configurations relying on flexible electrolysis alone. By 2035, flexible H2-DRI-EAF can achieve near cost parity with conventional steelmaking under moderate carbon pricing ($38/t CO2) and 50% low-cost scrap addition. Flexibility systematically alters investment patterns through significantly reducing the required capacities of solar and energy storage while moderately inducing differentiated overcapacity in electrolyzers, DRI furnaces, and EAFs. For a 1 Mt/year H2-DRI-EAF plant, renewable deployment exceeds 100 km2; a PV-only configuration halves the land footprint but raises LCOS by $5–64/t. This study provides quantitative insights to support the scalable deployment of green steel pathways under high renewable penetration.

Industrial sectors such as cement and chemicals are central to economic development but account for a growing share of global CO₂ emissions. Green hydrogen and carbon capture, utilization and storage (CCUS) are widely viewed as essential options for deeply decarbonizing these “hard-to-abate” industries, yet their high costs and infrastructure needs remain major barriers to deployment at scale. New opportunities emerge when green hydrogen production is coupled with oxy-fuel cement kilns and CO₂ capture, so that by-product oxygen and captured CO₂ are reused within an integrated co-production system. Here we show how industrial symbiosis between cement production and methanol synthesis can create bidirectional molecular flows and lower costs. We combine an hourly resolved plant-level optimization model with CCS source–sink matching to explore system configurations, flexible operation under variable renewable electricity, and plant-by-plant deployment pathways for China’s cement fleet. Our results show that co-producing clinker and green methanol cuts costs significantly relative to decarbonizing cement and methanol separately, while reshaping the national CO₂ network. Beyond this specific case, the framework shows how coupling hydrogen, CO₂ and O₂ flows across sectors can inform infrastructure planning and circular-economy policy for industrial decarbonization.