The USS Nimitz has returned to its Everett homeport after a 70-day exercise.

Capt. Jeff Ruth, the Nimitz's commanding officer, says the crew has been performed numerous tests, passed many inspections and led 22 nations through exercises.

During the training, Nimitz tested the use of bio-fuel on carrier-based aircraft.

The demonstration was a step toward the Department of the Navy's goal to reduce consumption of energy, decrease reliance on fossil fuels and significantly increase the use of alternative energy.