In-situ data vs. bottom-up approaches in estimations of marine fuel consumptions and emissions

Pollution by marine fuels and their influence on ecosystems and the human populace are growing concerns in the maritime industry. Consequently, emission regulations, alternate marine fuels and fuel efficiency enhancements are being pursued to ensure that marine emissions are curtailed within acceptable limits. Many strategic decisions related to these areas are taken based on cost and emission estimates which in turn depend on the accuracy of the estimation of marine fuel consumptions. The estimates are based on various methodologies which attempt to capture maritime fuel consumptions at local, regional and global levels. The bottom-up approach is the most predominant method to estimate emissions and thereby to assess compliance with the emissions regulations. The bottom-up methodologies rely heavily on average values of specific fuel consumptions and engine load factors. A case study which utilizes in-situ data is conducted to investigate the accuracy of the current approach and the results are compared with the estimates based on bottom-up approaches found in the literature. The findings revealed significant variations between the estimates and the actual fuel consumptions informing implications of unrealistic cost and emission estimates. As a solution the paper suggests a new concept in order to establish more reliable estimations of fuel consumptions and hence emissions predictions.