Lubricants: Meeting the VGP

Choosing the most effective lubricant to comply with the Vessel General Permit is not as straightforward as it might appear. ExxonMobil’s Iain White, Global Marketing Manager, Marine Fuels and Lubricants, explains that not all environmentally acceptable lubricants are the same:

With the introduction of controls over discharges from all oil-to-water interfaces into U.S. waters, vessel operators need to be aware of how these regulations affect them and what they must do to comply. 

In order to operate within the law, vessel operators must use environmentally acceptable lubricants (EALs) on any equipment that could possibly release oil into the water. However, not all EALs are created equal – those based on synthetic esters offer significant advantages over other common base stocks. 

The Vessel General Permit

The US Environmental Protection Agency (EPA) regulates discharges related to the normal operation of commercial vessels through its Vessel General Permit (VGP). This permit applies to vessels operating inside U.S. waters: within three nautical miles of the U.S. coast and also the Great Lakes. Currently it applies to vessels greater than 79 feet in length, with some exceptions including armed forces vessels. 

The latest amendments to the VGP stipulate the use of EALs in all oil-to-sea interfaces: equipment where seals or surfaces have the potential to release oil into the sea. The EPA also strongly encourages the use of EALs in above-deck equipment as well.

What is an EAL?

EALs are defined in the VGP as lubricants that are biodegradable, minimally toxic and are not bioaccumulative. Furthermore, for the purposes of the VGP, each component of the lubricant formulation that is not biodegradable has to undergo one of a range of tests to confirm that it is not bioaccumulative. Tests include checking a component’s molecular mass and diameter as well as its solubility in the marine environment. 

Selecting the appropriate product

Choosing the right lubricant for oil-to-water interfaces – including stern tubes, thrusters, bearings and mechanical equipment subject to immersion such as dredges and grabs – is clearly essential, so it is therefore crucial that vessel operators are aware of the types of products available to replace mineral oils.

There are three common EAL base stock categories: polyglycols, vegetable oil and synthetic esters.

Depending on the composition, polyalkylene glycol (PAG) based EALs offer a range of benefits including excellent lubricity, good load-bearing characteristics, low temperature properties, high flash points and good biodegradability. They are, however, highly incompatible, making changeovers very costly.

Naturally derived vegetable-based lubricants are readily biodegradable and offer excellent lubricity but are water sensitive. They also have poor resistance to temperature extremes.

The best solution

Currently, the most effective EALs are based on synthetic esters. They perform well across a wide range of temperatures, possess good lubricity and provide excellent corrosion protection. They also offer excellent biodegradability and exceptional protection from water contamination. Most importantly, they have a long history of proven performance, outstanding lubricant life, and compatibility with mineral oils, making changeovers straightforward.

Conversion from existing mineral oil products to EALs will require time in dry dock for some applications. It is therefore essential that the changeover process is as easy to manage as possible. Vessel operators will want to avoid the need for solvent flushing, as required for polyglycols, while also ensuring that their EAL is up to the job.

The optimal solution is therefore an EAL based on synthetic esters as this will ensure total compliance with EPA regulations; provide minimal downtime and offer the best overall protection.

Environmentally Acceptable Lubricant criteria 

To meet the VGP standard an oil must possess three characteristics.

Biodegradable: A minimum of 60 percent biodegradation within 28 days for 90 percent of the lubricant formulation or 75 percent of the grease formulation. The finished lubricant may contain up to 10 percent of components not meeting the 60 percent threshold of biodegradability and up to 5 percent of non-biodegradable (but not bio-accumulative) components. For grease, 25 percent may be either inherently or non-biodegradable (but not bio-accumulative).

Minimally toxic: The finished product must pass acute or chronic toxicity tests or, as an alternative, an evaluation may be conducted on a constituent basis where the ‘lethal concentration’ or the ‘no observed effect concentration’ is measured. 

Non-bioaccumulative: Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than the speed at which the substance is lost. Consequently, to qualify as non-bioaccumulative a substance must not be able to build up to toxic levels.