Effects of fuel-specific energy and operational demands on cost/emission estimates: a case study on heavy fuel-oil vs liquefied natural gas

Maritime industry is in constant pursuit of viable alternatives in order to comply with present and imminent regulations which address pollution by marine fuels. Cost/emission estimates, which determine the efficacy of compliance options, rely heavily on bottom-up methodologies for estimating fuel consumptions. These methodologies employ representative databases for their estimates instead of actual in-situ data. The use of in-situ data is therefore of paramount importance for accuracy of end results on which industry-wide strategic decisions are based.

Moreover, total fuel consumption of a potential alternative is calculated simply using energy conversion factors in comparison to a conventional fuel. However, each compliance-option comprises of unique process-components which demand diverse operational, electrical and heating energy requirements which in turn alter their fuel consumptions and emission inventories. Therefore, each compliance-pathway should be assessed individually using in-situ data in order to estimate fuel consumptions and emission inventories rather than using energy conversion factors between them.

A case study which utilizes in-situ data is conducted to assess the effect of fuel-specific processes on energy/operational demand and the emission estimates between residual heavy fuel-oils and liquefied natural-gas for a bulk carrier. The findings reveal that allocation and apportion of fuel-specific electrical/heating energy demands as well as operational components to each compliance option would produce more accurate emission estimates as well as realistic cost comparisons. Moreover, the study endorses that the use of natural gas as a marine fuel is highly commendable and asserts that in fact more emission reductions can be achieved than previously estimated.