From the early 19th century to well into the 20th century, steamboats took command of the world’s oceans. The emergence of this new marine technology led to the elimination of sailing ships from the commercial shipping realm. In the latter half of the 20th century, the motor ship began to reign supreme.
The diesel engine made its debut in 1892, thanks to Rudolf Diesel, while the four-stroke marine diesel engine ship embarked on its maiden voyage two decades later. Two-stroke designs emerged in the 1930s, offering a quicker and more imposing marine vessel. In the interwar era, the portion of marine engine-driven ships grew to a quarter of total ocean-going fleet tonnage. This preceded a succession of diesel engine improvements which enabled the use of heavy fuel oil in mid-sized speed trunk piston engines.
High alkalinity cylinder lubricants materialised in the mid-20th century to neutralize acids produced by the combustion of high sulfur residual fuels, with wear rates comparable to those generated by distillate diesel fuel.
Running on diesel fuel, diesel ships gained traction in the mid-1960s. At this time, steamships were capsized by motor ships, both in sheer numbers and gross tonnage. By the dawn of the 21st century, motor ships accounted for nearly 100% of the world fleet.
In recent years, marine emissions have received increasing scrutiny from the International Maritime Organization (IMO), environmental agencies, and public health advocates. The unifying objective of these disparate entities is the reduction of ship emissions to improve air quality and to mitigate the impact of climate change.
Preliminary regulations have focused on reducing sulfur oxide (SOx) and nitrogen oxide (NOx) emissions where vessels operate in close proximity to people — such as in coastal and port vicinities. The IMO’s upcoming 2020 global sulfur cap will strengthen emissions standards even further, imposing stricter limits on SOx emissions in waters outside of coastal zones.
SOx emissions are based on the level of sulfur content in the fuel and can be mitigated using low sulfur fuel oil or alternate technology — such as an exhaust gas cleaning system. An added bonus of reducing SOx emissions is a decrease in the level of particulate matter (PM), a pollutant regulated by the United States Environmental Protection Agency (EPA).
IMO MARPOL Annex VI, Regulations for the Prevention of Air Pollution, is the preeminent international regulatory body in place for monitoring ship emissions. The regulation puts a limit on fuels containing a sulfur content of up to 0.5% and will be enacted worldwide from 1 January 2020. Regulation 2.9 of Annex VI advises that SOx emission controls apply to all fuel oil used in combustion equipment and devices onboard, barring the installation of a sanctioned exhaust gas cleaning system, such as scrubber systems. Vessels may opt to use low sulfur content marine gas oil (MGO) or 0.10% heavy fuel oil (HFO) specifically developed for use in emission control areas (ECAs).
As the 2020 IMO deadline draws near, the industry is considering available fuel options and the impact on their fleets.
The majority of marine engines in operation today are designed to burn HFO or marine diesel oil (MDO). Design modifications, as well as operational adjustments, may be needed for engines and equipment to use alternative fuels.
Marine diesel engines use fuels which comprise of highly finished petroleum-based products mixed with chemical additives. Specific energy content, ignition quality, unique gravity, and many other fuel and oil properties are related to the hydrocarbon composition. Complete and incomplete combustion of fuel in the diesel engine results in the formation of a complex mixture of gaseous and particulate exhaust. During combustion, sulfur compounds in the fuel are oxidised to form sulfur dioxide (SO2) and sulfur trioxide (SO3) — collectively known as SOx.
Particulate matter is a complex mixture of tiny particles and liquid droplets, including components such as acids, organic chemicals, metals, and dust particles. Exposure to PM, which can be found in the emission stream, has been associated with serious cardiovascular and respiratory health complaints. The level of SOx and PM present in the exhaust stream can be significantly reduced by burning cleaner, low sulfur fuel oils such as marine gas oil, and low sulfur (0.10%-0.50%) heavy fuel oil. The global use of low sulfur fuel will be compulsory from 2020, unless alternative technology, such as an exhaust gas cleaning system, is used. NOx compounds are not impacted drastically by the type of fuel burned; however, they can be mitigated by moderating the combustion process.
Environmental considerations have resulted in both the voluntary and compulsory use of biodiesel in on-road diesel for passenger cars and heavy-duty vehicles. This trend is infiltrating sectors of the marine industry. Blends of renewable bio-derived fuels are considered a possible alternative energy source and may result in a reduction of greenhouse gas (GHG) and SOx emissions.
A fuel switching advisory notice was first published by the American Bureau of Shipping (ABS) in March 2010, with a revision in 2014. This declaration offered new guidelines for shipowners, builders, and operators to navigate the risks of fuel switching and to educate them on preferred practices. A recent Marine Fuel Oil Advisory has also been released with the upcoming IMO 2020 guidelines.
This document offers advice on various aspects of marine fuels, most notably fuel specifications, quality, and relevant considerations prior to and during use. The information will educate the sector on applying the 2020 requirements to enable a more smooth-sailing future.