Understanding Fatty Acid Methyl Esters

This "Chemical of the Quarter" excerpt is from the U.S. Coast Guard “Proceedings of the Marine Safety & Security Council” magazine, by Mr. Tom Felleisen, lead chemical engineer for bulk liquids and gases in the Hazardous Materials Standards Division.



Fatty Acid Methyl Esters

What is it?
Fatty Acid Methyl Esters (FAME) is the product shipping name for biodiesel, a replacement fuel for petroleum-derived diesel oil. FAME can be produced from animal fat or vegetable oil, including waste oil from fast food retailers.

How is it shipped?
On barges, FAME can be carried as a Grade E combustible liquid. For the purposes of the Oil Pollution Act, FAME is considered oil. Under the International Convention for the Prevention of Pollution from Ships, FAME carriage must be on a Type 2 chemical carrier (double-hull).

Why should I care?
Shipping concerns. For the past several years, FAME shipments have been increasing. Since oceangoing ships must meet MARPOL Annex II requirements, there could be a significant rise in the number of certificates of compliance as the use of chemical tankers increases incrementally.

Health concerns. There are no significant health concerns. However, the International Bulk Chemical Code does indicate that FAME has a safety hazard based on an estimate of the effect of a fine mist of FAME being accidentally inhaled. In making that safety hazard determination, however, there was no evidence that such a mist could be made under normal conditions, so the hazard is purely hypothetical.

Fire or explosion concerns. For FAME, the concerns about fire or explosion are, in a way, the opposite of what one normally considers. In particular, FAME has a flashpoint above and an energy density below those of petroleum-derived diesel.

Therefore, it is safer than diesel, but in consequence engine performance parameters must be adjusted to take those differences between FAME and diesel into account. Since FAME is a combustible liquid, it does not require an inert gas system for fire protection. Nonetheless, inert gas may be needed to keep FAME from absorbing water vapor that is in the same tank.

FAME is unusual because it will not dissolve in water (the technical term is “hydrophobic”), but it will absorb water (it is “hygroscopic”). Compensating for those properties is not too difficult when shipping by vessel, but those properties mean that it may not be able to reach major markets using existing oil pipelines.

What’s the Coast Guard doing about it?
Current enforceable regulations for FAME need to be brought up to international standards, but overall existing methods of carriage by tank vessel already provide an excellent level of safety and environmental protection.


For more information:
Full article is available at: http://www.uscg.mil/proceedings/summer2009/articles/69_Felleisen_Chemical%20of%20the%20Quarter.pdf .

Subscribe online at http://www.uscg.mil/proceedings/subscribe.asp.