Abstract: Aquatic nuisance species (ANS) in ship's ballast water are killed by permeating to equilibrium a gaseous mixture consisting essentially of, preferably, ≧84% nitrogen, ≧11% carbon dioxide and ≦4% oxygen through ship's ballast water until the ballast water itself becomes (i) hypercapnic to ≧20 ppm carbon dioxide, and, by association, (ii) acidic to pH≦7, while preferably further, and also, being rendered (iii) hypoxic to ≦1 ppm oxygen. The permeating is preferably realized by bubbling the gaseous mixture preferably obtained from an inert gas generator through the ballast water over the course of 2+ days while the ballast water is continually maintained a pressure less than atmosphere, preferably −2 p.s.i. or less.

Abstract: The ullage space gases of a ship's ballast tanks (i) are depressurized to a pressure less than atmosphere—called an “underpressurized” condition—of most preferably about 14.7 PSIA or lower, simultaneously that (ii) they are inerted, preferably to <4% O2 and more preferably to <2% O2. Oxygen within the ballast water is rapidly, preferably within hours, substantially depleted, preferably to <1% PPM and more preferably to <0.6 PPM, by circulating these inerted ullage space gases through the ballast water as bubbles, removing oxygen from the ballast water more by outgassing than by diffusion. The rapidly de-oxygenated ballast water is preferably so maintained for the substantial portion of the ship's voyage, which is effective in killing most aerobic aquatic life within the ballast water.

Abstract: Upon loading of oil cargo the ullage space of a tank of an oil tanker is sealed substantially gas tight with the gaseous contents of the ullage space both (i) initially inerted so as to be incapable of supporting combustion of any oil within the tank, and (ii) at an initial pressure less than atmosphere. The tank is preferably continued closed, preferably optionally with closed loop recirculation for purposes of gas mixing, for the entire voyage of the tanker save that (1) ullage space gas pressure uncommonly exceeds limits because of any of (i) leakage of atmospheric gases into the tank, and/or (ii) outgassing of gases within the oil contents of the tank, (iii) evaporation of the oil or portions thereof, and/or (iv) expansion of the ullage space gases upon thermal heating, and/or (2) free oxygen within the ullage space gases exceeds limits because of any leakage of atmospheric gases into the tank, at which time the tank is re-inerted, preferably with flue gases, or again de-pressurized, as and when required.