As a pioneering field in marine resource development, deep-sea mining is progressively advancing from theoretical investigation into a stage of commercial exploitation. This study focuses on the economic analysis of commercial mining of deep-sea polymetallic nodules, and summarizes key components and methodologies for economic evaluations. A comprehensive and practical economic analysis framework has been established. Two representative international deep-sea polymetallic nodule mining projects have been selected for economic assessment and comparative analysis using the aforementioned framework. Through sensitivity analysis, the potential impacts of uncertainty factors on project economic benefits are evaluated, providing decision-makers with scientifically grounded support for investment decisions.

With the increasing depletion of global land resources, deep-sea polymetallic nodules, as a potential and abundant mineral resource, have attracted widespread international attention. This paper systematically elaborates on the operational process and equipment composition of deep-sea polymetallic nodule mining, reviews the progress of domestic and foreign experimental activities in the field of deep-sea polymetallic nodule mining, and focuses on sorting out the key equipment and technologies applied or developed globally in aspects such as deep-sea mining platforms, underwater collection systems, mineral lifting systems, and environmental monitoring systems. After analyzing the gap in the development of domestic equipment technology, this paper puts forward targeted suggestions, aiming to promote the development of China’s deep-sea polymetallic nodule mining equipment technology, in order to realize the development and utilization of deep-sea mineral resources.

The bulk carrier with low additional value is difficult to choose the decarbonization path due to the cost control. The current study qualitatively analyzes the applicability of carbon capture system on the bulk carrier, and quantitatively analyzes the applicability of alternative fuel, such as biodiesel, LNG, grey methanol, green methanol, green ammonia, on the bulk carrier. The carbon capture system is not suitable for the bulk carrier, because it has problems such as the high energy consumption for capture, the CO ₂ storage tanks occupying the cargo tank volume, and the captured CO ₂ that is difficult to handle. The preliminary economy calculation of the alternative fuel is relatively poor due to the high cost and the capacity loss of the cargo tank that was caused by the low volume energy density. Considering that the use of the conventional fuel may face carbon tax, the green ammonia powered ship has certain advantages when the carbon tax is above 439 dollars/t, and the green methanol has application advantages when the carbon tax is above 692 dollars/t.

Starting from the investigation of domestic ship owners, the application of alternative fuels to international ships has been analyzed in view of the concerns of ship owners, such as fuel supply, main engine technology and fueling infrastructure. The results show that LNG, as the most mature alternative fuel at present, possesses great potential for further development in the short and medium term, while methanol and ammonia have increasing share in the medium and long term. It is predicted that the proportion of ocean-going alternative fuel powered ships in 2030 and 2040 is only 5% and 11%. In order to cope with the general trend in the future, it is necessary to accelerate the development of the methanol and ammonia internal combustion engines suitable for ocean-going ships, and launch demonstration projects of low-carbon synthetic fuels such as ammonia and methanol as soon as possible, as well as simultaneously develop corresponding innovative ship types to achieve independent control of the main engine and fuel supply.