A data-driven study of IMO compliant fuel emissions with consideration of black carbon aerosols

Abstract

The shipping industry has been facing increasing pressure to reduce environmental emissions. For instance, starting in 2020 the International Maritime Organization (IMO) required a reduction of the global sulfur limit for shipping fuels outside designated Sulfur Emission Control Areas (SECA) from 3.5% to 0.5% on a mass basis. Other pollutants are also being targeted for short-term and long-term reduction.Aiming at providing sustainable fuel solutions for the stage of tank to propeller, this manuscript evaluates various shipping fuel options focusing on quantitatively comparing the fuel consumption and emissions of major air pollutants. A bottom-up emission inventory model is developed by analyzing and optimizing multiple sources of load factors, specific fuel consumption and emission factors. Rather than taking deterministic emission leading values, this work improves the model quality by considering external factors and the latest emission data and processing a detailed ship-by-ship calculation for the ship database collected by the shipboard Automatic Identification System (AIS). The amounts of carbon dioxide for the main engine, auxiliary engine and auxiliary boilier are firstly calculated, and then the fuel consumption per nautical mile are computed by integrating CO2 intensity. Next, ship exhaust gases are calculated for two categories: (i) gases impacting the global warming potential (GWP) and (ii) the non-GWP gases. Besides sustainable solutions within one specific ship fleet, this work firstly establishes a nautical mile-based fuel consumption per unit of capacity bin for major merchant ships to serve as a basis for finding an optimized fuel solution among different ship types. In addition to addressing the typical ship-source pollutants, this work also focuses on negative environmental effects resulting from BCA because it has not been thoroughly considered in the literatures despite its contribution to GWP. To illustrate the value and applicability of the proposed approach, a case study is solved to estimate the cumulative fuel consumption and GWP-related gas emission inventory for a transoceanic trip from Houston to Rotterdam. The results demonstrate that the GWP gas emissions of heavy fuel oil with scrubber are 38% more than those of one LNG dual-engine option. Explicit consideration is also given to BCA emissions. The results indicate that the blended fuel aimed at satisfying the IMO 2020 Sulfur Cap does not perform well in BCA emission control.