By Judith Burns
Science and Environment Reporter
The ship Kaisei which left San Francisco today
The second of two research ships bound for a huge "island" of plastic debris in the Pacific Ocean leaves San Francisco today.
Ocean currents have pushed the refuse together in an area estimated to be larger than the State of Texas.
The expedition, named Project Kaisei, will study the impact of the waste on marine life.
Ultimately the organisers hope to clear the plastic and recycle it for use as fuel and new products.
Speaking from the quayside in San Francisco, waiting for the second ship to leave, Ryan Yerkey, the project's chief of operations, told BBC News: "Every piece of trash that is left on a beach or ends up in our rivers or estuaries and washes out to the sea is an addition to the problem, so we need people to be the solution."
"Twenty years from now we can't be harvesting the ocean for trash. We need to get it out but we need to also have people make those changes in their lives to stop the problem from growing and hopefully reverse the course."
The two ships, Kaisei - which left today - and New Horizon from the Scripps Institution of Oceanography - which left on 2 August - will take five days to reach the debris.
They will return at the end of the month.
The vortex of currents which pushes the debris together is known as the North Pacific Gyre.
Ryan Yerkey has sailed across the Pacific twice and has watched the problem build up since the 1980s. He blames our increased use of disposable products.
He said: "You are talking about quite a bit of marine debris but it's not a solid mass. A lot of the items have broken down. Of course there are larger items out there. But the items, depending on the density and the state they're in, can be anything from the surface down to 20ft to 30ft (6m to 9m) deep."