Development of exhaust emission factors for vessels: A review and meta-analysis of available data

The maritime sector is characterized by high contribution in the emission of harmful pollutants such as NOX, PM, and SOX. The sector is making decisive steps to drastically reduce its environmental footprint by applying new technology and fuels as a reaction to the increasingly stringent emissions regulatory framework. In order to calculate the contribution of shipping to current emission inventories and to project future developments under different policy scenarios reliable and diversified emission factors have to be developed. In this context the present paper develops a new set of emission factors for ships, based on a review and statistical processing of shipping emission measurements available in literature. To offer significant resolution and versatility for use under different operating conditions, the developed emission factors are expressed as a function of the ship engine load. These emission factors are also distinguished according to the engine and fuel types that are met in practice. The absolute values of the developed emission factors highlight the emission performance of ships per pollutant, while the load dependent functions produced reveal how this emission performance of ships changes under various operating conditions. Finally, a comparison of the developed load dependent emission factors with modal emission factors retrieved from literature is performed specifically for NOX emissions. This comparison indicates the differences and similarities between the two methods as a measure of uncertainty in the estimation of emissions using the proposed emission factor dataset.