Port Electrification Series, Part 2

In part 1 of this series, we looked at the Port of Los Angeles’ commitment to one of the most aggressive clean-air strategies in the country, its Clean Air Action Plan (CAAP).

The sophomore slump is the enemy of every success story. Early emissions reductions achieved by CAAP were a victory, leveraging clean trucks, shore power for docked ships, and modern cargo equipment. But a sophomore slump lurked as gains became largely exhausted 20 years later.

Remaining port emissions are now concentrated in fewer sources. The 2017 update to CAAP shifted attention toward equipment and systems that had been previously considered too complex, too distributed, or too operationally sensitive to change.

One of the most significant remaining producers of emissions at the Port of Los Angeles is its tugboats, which account for less than one-fifth of harbor craft but contribute nearly a third of harbor craft nitrogen oxide (NOx) emissions. But any interruption to their services could bring the port to a standstill.

What Do Tugboats Actually Do at a Port?

The duties performed by tugboats are far more consequential than what the cute toys kids play with in the tub imply. They are the pound-for-pound champions of critical port operations across the world. Ship assist is one of their core functions at the Port of Los Angeles, guiding massive, plodding, 100,000+ metric-ton container vessels in and out of berth safely. Tugs facilitate the precision needed to maneuver tight harbor channels amidst wind, current, and inertia.

Container ships at the Port of Los Angeles typically measure approximately 1,000 feet in length. By comparison, tugboats tend to stretch only 90 feet long and less than 1,000 tons of weight. To move their massive counterparts, tugs operate at extremely high load during ship assist operations.

With roughly 17% of all US containerized trade passing through the Port of Los Angeles, operators of the harbor’s approximately 12 assist tugs are privy to a unique view of the immensity of American trade. Put another way, if tug operations were to stop or get delayed, so too would vessel movement, cargo delivery, and a significant portion of the American economy.

Emissions Concentration: Small Fleet, Outsized Impact

Harbor tugboats pack an enormous amount of punch under the hood. To generate the high bollard pull needed to maneuver the largest container vessels, tugboat engines deliver significantly more power than the vessels they assist, prioritizing thrust and torque over cargo capacity.

To punch so far above their weight, harbor tugboat engines produce anywhere from 2,500 to 4,000 horsepower. They burn through tens of thousands of gallons of diesel fuel per tank. That is why their intense duty cycles contribute disproportionately to NOx and diesel particulate matter (DPM) emissions compared to lighter port equipment.

According to port inventories, tugboats can produce about 144 tons of NOx annually, nearly 30% of all total harbor craft NOx emissions. They also can account for roughly 3 tons of DPM annually, about 30% of total harbor craft DPM emissions. With tugs comprising approximately 19% of harbor craft, their emissions leave an outsized environmental impact.

Tugboats and the Port’s Next Phase

Decarbonization is evolutionary. Through CAAP, the Port of Los Angeles tackled emissions by targeting low-hanging fruit. Trucks have been modernized, shore power adopted, and cargo-handling equipment upgraded. With them, the emissions curve flattened.

Remaining port assets will be the most difficult to change. Emissions are concentrated in fewer sources. Solutions are not ready-made.

Finding a way to clean tugboat emissions would be a big win since they are so small in number and high in environmental impact. But avoiding disruption to tug operations is critical. Any loss of service would carry great ramifications to the port and the American economy. Threading this needle is delicate.

The next emissions frontier lies in electrification. It has not been viable for tugboats, until now.

Coming soon, the technical challenges of building electric tugboats.