The figures below represent five generations of Solvang’s 60,000 cbm class LPG carriers. Data represent measured fuel consumption; NOx emission before TIR I is set to TIR I level. In this period, fuel consumption and hence CO2 emissions got reduced by 50 percent, while NOx emissions dropped by approximately 65 percent.
The emission reductions represent a combined output from a large number of design and operational measures.
Another method for measuring the environmental performance of a vessel, is the ESI (Environmental Ship Index). This index use NOx, SOx and CO2 emissions, representing a maximum value of 100.
The table clearly shows the effect of the exhaust gas cleaning on Clipper Harald (1999), cleaning NOx and SOx from discharges. Clipper Quito (2013), Posh (2013), Jupiter (2015), Saturn (2015) and Venus (2015) likewise score better, as they have Tier II NOx emissions plus exhaust gas cleaning. Clipper EOS, EYNO, ERIS, EIRENE and WILMA (all delivered 2019), have Tier III NOx emissions plus scrubber.
If equipped with shore power connection, these vessels would score closer to 100. Clipper FREEPORT and VANGUARD delivered in 2017, will get retrofit EGC to perform at the same level as other same generation vessels in Solvang´s fleet.
The IMO EEDI (Energy Efficiency Design Index) for different vessel generations showed in figure above, reflect vessels´ performances related to CO2 separately. The conclusion coincides with ESI results. The MIPO 21K class exemplifies the significant performance improvement caused by Solvang environmental package (ECG, Mewis duct, twisted rudder, anti-fouling and ballast tank arrangements, etc.).
Shipping articles normally feature a picture displaying a vessel spewing abnormal smoke from the funnel. The plain implication is that shipping needs to shift to a “clean fuel”.
The real explanation for abnormal smoke is NOT “dirty fuel". All fuels create smoke if you run them through a diesel engine with poor combustion. Starting up a cold engine without heating is one obvious example, but it could be other technical problems too, like bad maintenance, improper design/setup, bad operation etc.
A well-tuned engine in normal operating conditions will produce low levels of visible smoke, except from low load operation on some engines.
Research literature shows a spread in smoke levels (particle emissions). In general, two-stroke engines on slow speed emit less smoke than four-stroke engines running on medium speed. Due to high sulfur contents, HFO yields more particles than MGO, when measured in grams per kWh. But even if HFO particles have higher contents of PAH, metals etc., MGO´s higher number of smaller particles imposes a graver effect on human health than does HFO.
If gauged after scrubbing/removing PAHs, nickel and vanadium from the exhaust, we should expect even better results for HFO.
FSN measurements on ethylene carrier Clipper Harald show smoke numbers below and/or far below visible smoke levels under all HFO operation conditions.
Supporting Literature on particles.
Particulate Matter from Both Heavy Fuel Oil and Diesel Fuel Shipping Emissions Show Strong Biological Effects on Human Lung Cells at Realistic and Comparable In Vitro Exposure Conditions (US National Library of Medicine National Institutes of Health )