Could a warship make useful methane from human waste?

Could a modern warship turn human waste into enough methane to power an aircraft or other systems?

Probably not; even a carrier crew is judged unlikely to produce enough waste for a reliable methane supply.

The objection is the amount of waste available from a modern crew. Even a large U.S. carrier's complement is judged unlikely to provide a dependable methane supply for powering aircraft. The comparison with several herds of cattle conveys the scale of the proposed fuel requirement; it is not a calculated output figure.