Analysis of emission reduction strategies for the use of alternative fuels and natural carbon sinks in international bulk shipping

• Scraping old ships could help mitigate climate change. • Carbon rights and natural carbon sinks are beneficial to carbon reduction. • Natural carbon sinks are more cost-effective than carbon rights. • Increased use of alternative energy cannot meet carbon reduction standards. This research examines four categories of international bulk carriers and forecasts their ability, from 2025 to 2050, to meet the IMO targets for emission reduction: a 20% reduction by 2030 and a 70% reduction by 2040 compared to 2008 levels, with the ultimate aim of achieving net-zero emissions by 2050, utilizing a life cycle assessment (LCA) methodology. It evaluates various scenarios involving different rates of ship demolition and alternative fuel adoption to achieve these targets. Additionally, it investigates the potential costs associated with carbon credits and natural carbon sinks (such as seagrass) in cases where emissions targets are not met. The findings suggest that, under the baseline scenario and Scenario 1, despite increased usage of alternative fuels and declining emission factors, none of the four ship types meet the IMO targets in terms of life cycle greenhouse gas (GHG) emissions. However, in Scenario 2, where the ship demolition rate steadily increases until the usage of traditional fuel ships reaches zero, and with concurrent reductions in emission factors, emissions decrease substantially and approach the desired targets, though they still fall short. Furthermore, the study analyzes the financial implications of employing carbon credits versus natural carbon sinks to offset emission shortfalls, indicating that Scenario 2 is comparatively less costly. It also demonstrates that leveraging natural carbon sinks is more cost-effective in reducing emission expenses compared to relying solely on carbon credits. Consequently, the research recommends prompt adoption of alternative fuels, acceleration of ship demolition rates, and utilization of natural carbon sinks not only to meet international shipping emission reduction objectives but also to rejuvenate marine ecosystems, thereby fortifying marine environments.