Evaluating Exhaust Gas Economizers for Emission Reduction in Diesel-Powered Marine Vessels on Lagos Lagoon

The maritime transport sector is a cornerstone of national and global logistics, facilitating the movement of goods and passengers across inland waterways. In Nigeria, the Lagos Lagoon hosts thousands of diesel-powered marine vessels including passenger ferries, cargo barges, and fishing boats, which emit substantial quantities of carbon dioxide (CO₂), contributing to climate change and local air pollution. Waste heat recovery (WHR) via exhaust gas economizers (EGE) presents a cost-effective approach to improving energy efficiency and reducing emissions in these vessels. This study assesses the potential of EGEs as a waste heat recovery solution for diesel-powered marine vessels operating in Lagos Lagoon. Using standard emission factors and thermodynamic calculations, the fuel consumption, CO₂ emissions, available exhaust heat, recoverable heat, fuel savings, and emission reductions are quantified for three representative vessel categories: Passenger Ferry (A), Cargo Barge (B), and Fishing Boat (C). Results show that with an economizer effectiveness of 70%, recoverable heat amounts to 3,586.8, 1,694.8, and 789.1 MJ/day respectively. Equivalent fuel savings are 93.33, 44.10, and 20.53 kg/day, with corresponding CO₂ reductions of 299.23, 141.38, and 65.83 kg/day. These findings demonstrate that EGE-based WHR systems can achieve meaningful emission reductions and operational cost savings in inland waterway vessels. Recommendations for practical adoption are provided, including simplified system designs, stakeholder collaboration, and supportive policy frameworks.