What is bunker oil? Nothing you want to touch, expert warns

A spill response boat works to clean up bunker fuel leaking from the bulk carrier cargo ship Marathassa anchored on Burrard Inlet in Vancouver, on Thursday, April 9, 2015. (Darryl Dyck / THE CANADIAN PRESS)

As crews raced to contain a spill of bunker oil in Vancouver’s English Bay Thursday, many wondered exactly what the toxic slick was made up of.

Heavy bunker oil is created from the residue left from petroleum after it is distilled to create more expensive products like gasoline and diesel, says Brian Noronha, a marine engineering instructor at the BC Institute of Technology.

“It’s usually cut with lighter stock to make it more pumpable, so it can be burned in the engine of a ship,” Noronha told CTV News Thursday. “It is extremely heavy and extremely dense, and even after cutting it can still have a density greater than water.”

But Noronha couldn’t say whether that was the case in the English Bay spill, as the density of bunker oil depends on where the petroleum is sourced from and how much diesel it is cut with.

Regardless of density, Noronha said the only way to get rid of it is to contain it with a boom and pump it out of the water.

“In the long term it would eventually dissipate,” Noronha said.

The fuel, which the City of Vancouver warned is toxic, can cause serious health issues to people and animals who come into contact with it, he said.

If an unlucky bird was in the path of the spill, “I think they would probably get covered up in it and probably won’t be able to fly,” he said. “I don’t think the bird has a chance.”

Noronha related a story from one of his former students who served on a vessel in the Great Lakes, who said she developed an instant rash after coming into contact with bunker oil.

It’s unclear how long the oil can last in water before it fully breaks down and dissipates.

A 2007 study by the University of Hamburg found that bunker oil “may be expected to persist due to its greater proportion of non-volatile components and its high viscosity.”