There are several options that existing ship owners/operators can utilize to reduce ship emissions and their related impacts. A variety of approaches are available to target emission reductions from the two primary emissions sources on ocean-going vessels: main engines and auxiliary engines. Main engines are generally large direct drive engines, two stroke, slow speed, and massive. Auxiliary engines are generally medium speed engines and can range from small to large. The information below provides an overview of options available to reduce emissions from vessel engines and provides links for further information.
Existing vessels can become significantly cleaner, with respect to air quality, if at a minimum the following elements are incorporated into existing vessel’s operations:
Cleaner Fuels
Moving to the use of cleaner, distillate marine fuels for both auxiliary and main engines with low sulfur levels helps reduce sulfur oxide (SOx), particulate matter (PM), and nitrogen oxide (NOx) emissions. In the Ports’ Clean Air Action Plan (CAAP), use of cleaner 0.2% sulfur distillate fuels in both main and auxiliary engines is recommended (CAAP Measures OGV3 & 4). The benefits from using these fuels are best when ships are near shore and therefore closer to populated areas. Switching to marine diesel oil (MDO/DMB) and marine gas oil (MGO/DMA) with the lowest available sulfur is recommended within 40 nautical miles (nm) of Point Fermin. Port of Los Angeles prepared a fuel study for the Pacific Rim in 2005. The Ports of Long Beach and Los Angeles are partnering with the California Air Resources Board to develop a detailed and updated low sulfur fuel availability study over the next several months.
Vessel Speed Reduction
Since 2001, the Ports of Long Beach and Los Angeles have participated in a very successful voluntary vessel speed reduction (VSR) program. Since 2005, the Port of Long Beach has further increased compliance by offering the Green Flag Program, which provides financial incentives to their vessel carriers that participate in the program. To comply with the VSR Program (CAAP Measure OGV1) vessels reduce their speed to 12 knots on arrivals and departures to the Ports. Vessel speeds in the speed reduction zone are monitored and recorded in order to track compliance and to quantify emission reductions. Speed reduction is an operational change that all vessels can make to reduce both NOx and PM emissions, and it doesn’t require any modifications to the vessel. Emissions from vessels are directly related to the energy required to move the vessel through water. Even though at reduced speeds the main engines won’t be running at their lowest NOx and PM settings, the emission reductions associated with reducing the energy demand, or the load on the engine, significantly outweigh both the increased inefficiency of the main engine and increased auxiliary engine emissions (due to the longer transit time) from traveling at a slower speed. It is strongly recommended that ships calling on the Ports of Long Beach and Los Angeles comply with the VSR program and slow to 12 knots within 20 nm of Point Fermin. Also, as stated in the CAAP, the Ports will seek to move the VSR boundary out to 40 nm to increase emission reductions.
Slide Valves
Slide-valves are a new, more efficient generation of fuel injectors that reduce emissions of NOx and PM by minimizing the sac volume in the fuel-valve nozzle tip. Slide-valve technology was introduced in 2002 and today most MAN Diesel main engines are delivered with this technology. Slide-valves can also be retrofit in to existing MAN Diesel main engines. As stated in the CAAP, the Ports recommend that all vessels that can utilize MAN Diesel slide valves should have them installed.
Low Emissions Mode
Some vessel main engines, such as the MAN Diesel ME-C engines, can operate in a low NOx emissions mode. For vessels where this mode is available, it is recommended that the ship transit at 12 knots in this mode within 40 nm of Point Fermin.
Main Engine Retrofits
Other technologies for reducing vessel engine emissions are currently under development and testing. Much of the focus has been placed on reducing NOx emissions. Technologies such as selective catalytic reduction (SCR), sea-water scrubbers, dry low NOx combustion, humid air injection, water fuel emulsion, direct water injection, exhaust gas recirculation, electronic engine controls, etc. can be used but should be coordinated with the Ports’ Technology Advancement Program in order to expedite agency buy-in on the emissions reductions achieved.
Auxiliary Engine Retrofits
Auxiliary engines can be also be retrofit with SCR, sea water scrubbers, exhaust gas recirculation, in-line fuel emulsification, etc.Introduction of these technologies is recommended, however, both Ports strongly recommend that the integration of these technologies be coordinated with the Ports through the Technology Advancement Program to ensure that emissions reductions can be verified by the regulatory agencies.
At Berth Emission Controls
Additional options are being pursued by the ports to control auxiliary engine emissions while at berth. Significant emission reductions can be achieved by replacing the use of the ship’s auxiliary engines with plugging in to shore power. The Ports are currently developing the necessary infrastructure for vessels to begin plugging in and are placing requirements into leases to use the infrastructure (CAAP Measure OGV2). In addition, other technologies are being explored as alternatives for controlling at-berth emissions for vessels where shore power may not be appropriate. One such example, which is being demonstrated at the Metropolitan Stevedore Company in the Port of Long Beach, is the Advanced Maritime Emissions Control Systems (AMECS). This is system captures the ship’s exhaust and treats it onshore. This technology demonstration is currently being coordinated with the Ports through the Technology Advancement Program to ensure that emissions reductions can be verified by the regulatory agencies.
For all emission reduction strategies used to reduce emissions from vessels, it is important to inform the Ports so that the emission reductions can be quantified.
