Offshore hydrogen production presents a promising pathway for sustainable energy, leveraging wind-powered electrolysis and marine biomass conversion to generate hydrogen with minimal carbon emissions. However, the environmental footprint of offshore systems must be evaluated holistically, accounting for infrastructure construction, operational logistics, and long-term maintenance. This analysis contrasts offshore hydrogen production with land-based alternatives, focusing on emissions, corrosion challenges, and system durability.

Wind-powered electrolysis at sea capitalizes on high-capacity offshore wind farms, which generate electricity to split water into hydrogen and oxygen. The process itself emits no greenhouse gases, but the lifecycle emissions depend on the manufacturing, installation, and decommissioning of wind turbines, electrolyzers, and subsea infrastructure. Platform construction involves steel and concrete, materials with high embedded carbon. A typical offshore wind turbine foundation requires hundreds of tons of steel, with associated emissions from smelting and fabrication. Subsea cabling, necessary to connect turbines to electrolysis platforms, also contributes due to copper extraction and insulation materials.

Marine biomass conversion offers an alternative pathway, using algae or seaweed as feedstock for gasification or fermentation. While biomass growth absorbs CO2, the processing stages—harvesting, drying, and conversion—require energy, often derived from fossil fuels in current setups. Offshore biomass systems face additional challenges in transportation and storage, increasing their operational emissions compared to land-based facilities.

Maintenance logistics for offshore systems are more complex than land-based equivalents. Accessing turbines and electrolyzers requires specialized vessels, which consume diesel and emit CO2. Regular inspections and repairs, particularly in harsh marine environments, add to the cumulative emissions over the system’s lifetime. In contrast, land-based electrolysis plants benefit from easier access and lower transportation emissions for maintenance crews.

Saltwater corrosion poses a significant challenge for offshore hydrogen infrastructure. Electrolyzers and storage units exposed to marine environments degrade faster than those on land, necessitating corrosion-resistant materials like titanium or coated stainless steel. These materials are energy-intensive to produce, indirectly increasing emissions. Furthermore, saltwater intrusion can impair electrolyzer efficiency, requiring additional energy for purification or leading to more frequent replacements.

Land-based hydrogen production, particularly when powered by onshore wind or solar, avoids many of these marine-specific issues. Onshore electrolysis plants typically have lower infrastructure emissions, as they do not require massive steel platforms or subsea cables. Maintenance is simpler, with reduced reliance on fossil-fueled transport. However, land-based systems compete with other uses for limited space and may face higher electricity transmission losses if located far from renewable energy sources.

A critical comparison lies in the scalability of offshore versus land-based systems. Offshore wind farms can achieve higher capacity factors due to stronger and more consistent winds, potentially producing more hydrogen per unit of installed electrolyzer capacity. This advantage may offset the higher initial emissions from construction. Marine biomass conversion, while less mature, could utilize vast ocean areas without competing with terrestrial agriculture, though its efficiency and emissions profile require further optimization.

Quantitative assessments indicate that offshore wind-powered electrolysis can achieve emissions as low as 1 kilogram of CO2 per kilogram of hydrogen, assuming renewable energy powers all stages of the lifecycle. Land-based systems using grid electricity with a significant fossil component may range between 5 to 10 kilograms of CO2 per kilogram of hydrogen. Marine biomass systems vary widely, with emissions heavily dependent on feedstock type and processing methods.

The choice between offshore and land-based hydrogen production hinges on regional factors, including renewable resource availability, infrastructure costs, and environmental regulations. Offshore systems excel in regions with limited land but abundant wind or biomass resources, while land-based systems may be preferable where space and renewable energy are readily accessible. Both pathways require continued innovation to reduce emissions from materials, construction, and maintenance.

Corrosion management remains a pivotal issue for offshore hydrogen. Advanced coatings and cathodic protection can extend equipment lifespan, but these solutions add complexity and cost. Research into durable, low-emission materials is essential to make offshore hydrogen competitive. Similarly, optimizing marine biomass supply chains to minimize energy use will be crucial for reducing emissions.

In summary, offshore hydrogen production offers a viable route to low-carbon energy, but its emissions are influenced by construction, maintenance, and material challenges. Land-based systems provide a simpler alternative with lower infrastructure emissions but may lack the scalability of offshore solutions. Both approaches must address their respective limitations to play a role in a sustainable hydrogen economy. The decision to adopt offshore or land-based production should be guided by local conditions and long-term sustainability goals.