Scanning for Ideas: Ballast-Free Ship Would Keep Lakes and Waterways Clean
Freighters carrying water for ballast have introduced over 150 nonnative creatures into the Great Lakes, including the zebra and quagga mussels.
Edited by Stephen J. Mraz
These species often cause
havoc to other marine life and
man-made structures. There are
some moves to stop this, including
a recently enacted regulation that
says ships must flush their ballast
tanks with saltwater before entering
the St. Lawrence Seaway. There
are also mandates for expensive UV
or chemical-sterilization systems
for ballast tanks. But researchers
at the University of Michigan have
come up with a new idea, one based
on redesigning freighters and bulkcarrying
ships.
Ships carry ballast to stay stable
in the water when they are empty.
The new ballastless ship would
instead let fresh or saltwater flow
through the ship from front to
back. Water would travel slowly
through a series of pipes (called
trunks) that run below the waterline.
This would keep the ship stable
using local water. Ships would
no longer haul ballast water, along
with whatever is in it, from one
port to another.
Tests on a scale model in a towing
tank and a computer simulations
indicate the design would
also reduce the power needed to
propel a ship by 7.3%. For a 650-ft
freighter carrying 32,000 tons of
cargo from the Great Lakes to Europe
and back, that translates into
a fuel savings of roughly $150,000.