San Pedro harbor hybrid tugboat likely world's cleanest tugboat

What’s believed to be the only hybrid tugboat in the world is also very likely the cleanest one. A new study from UC Riverside looks at a boat used in the San Pedro harbor complex.

The Carolyn Dorothy has four diesel engines and 126 batteries. She’s a “dolphin class” tug – so to see exactly how much cleaner a hybrid tugboat could be, UC Riverside researchers had boat captains work that vessel alongside another dolphin class tugboat, the Alta June. It’s built by the same manufacturer with the same diesel engines and no batteries.

For months, sensors measured emissions from both tugs. The results were dramatic. Compared to the Alta June with the standard engines, the Carolyn Dorothy hybrid tug put out 27 percent less carbon dioxide, 51 percent less nitrogen oxide, and 73 percent less diesel soot.

Researchers say the Carolyn Dorothy could pollute even less if the tugboat plugged in at the dock more often. That may be a basis for future study – more plug-in power is coming to the harbor complex. So’s another hybrid tugboat, which will be working San Pedro Bay beginning the middle of next year.