CORONADO, Calif. » A Hawaii-based ship is joining the Navy’s “great green fleet,” operating on some version of alternative fuels.

In Coronado, Calif. Navy Secretary Ray Mabus struck a victorious tone as four ships left port to join the nuclear-powered aircraft carrier John C. Stennis.

The group will be joined off Hawaii by the destroyer Chung-Hoon.

The green initiative by the Navy and Marine Corps has been Mabus’ personal mission since 2009.

“The Navy has always been a leader when it comes to energy innovation,” Mabus said during a ceremony at North Island Naval Air Station.

“Sailors look out, they look to the horizon. They saw no obstacles. They saw the open sea,” he said, referring to the Navy’s history of embracing new power sources, from wind to coal to oil to nuclear reactors.

“I couldn’t be more proud of what sailors and Marines have done to free us, to give us operational flexibility in terms of energy.”

Mabus’ green fleet effort has been controversial at times — and to some degree, still is — because the cost of pure biofuel remains higher than petroleum.

The “green” cruiser and destroyers deployed Wednesday burned a petroleum-heavy blend of fuel — 90 percent regular ship diesel and 10 percent biofuel from beef fat.

The cost of fossil fuels has fallen so much in recent months that the Defense Logistics Agency was basically forced to use a low-biofuel blend to make its purchase for the green fleet competitive with straight petroleum. The 77.6 million gallons being used by the Navy for this demonstration project constitutes the largest buy of “drop-in” biofuel ever.

“This is the market. The price of oil has gone way down. This was bid out. We said give us the best blend you can give us. This was what came back,” Mabus said, in response to a reporter’s question Wednesday.

“But we’re not static. This is 2016. Our goal is to be at 50 percent by 2020. By doing this, this is a huge step.”

The blended biofuel used for the green fleet cost the taxpayers $2.19 per gallon — of which the U.S. Department of Agriculture covered 14 cents per gallon as part of an earlier announced deal to help the Navy and U.S. farmers.

The Defense Logistics Agency lists the price of standard ship fuel at $2.97.

The nuclear-powered aircraft carrier John C. Stennis, based in Washington state, and the San Diego-based cruiser Mobile Bay and destroyers Stockdale and William P. Lawrence make up the bulk of the “great green fleet,” which headed out on a regular seven-month deployment from Coronado on Wednesday.