Microwaves 'cook ballast aliens'

US researchers say they have developed an effective way to kill unwanted plants and animals that hitch a ride in the ballast waters of cargo vessels.

Tests showed that a continuous microwave system was able to remove all marine life within the water tanks.

The UN lists "invasive species" dispersed by ballast water discharges as one of the four main threats to the world's marine ecosystems.

The findings will appear in the journal Environmental Science and Technology.

Shipping moves more than 80% of the world's commodities and transfers up to five billion tonnes of ballast water internationally each year, data from the UN shows.

Vessels, especially large container ships, need ballast tanks to provide stability in the water and correct any shift in the ships’ mass.

When a ship's cargo is unloaded, it fills with ballast water; when it is later reloaded, often on the other side of the world, the water is discharged. - bbc