Monday, July 12, 2010

How much plastic is in the ocean ?

From Michael Reilly (DiscoveryNews)

Stiv Wilson of the ocean conservation group 5 Gyres has made a first attempt to tally how much plastic is in the global ocean.

We've all heard about the Texas-sized "garbage patch" swirling in the North Pacific, and recently we've been warned that the Atlantic's got a plastic problem, too. Rather than distinct patches, the planet's interconnected watery parts are effectively a thin soup of plastic refuse, with perhaps larger concentrations of rubbish in five large rotating gyres of water like the Pacific's.

The more people look, the more grim the situation looks. But how can we get our heads around how big the problem really is? How much plastic is really in the ocean, and can we clean it up?

In a new post on, Wilson takes what appears to be the first-ever stab at trying to figure it out.

The number he comes up with is staggering: he conservatively estimates there are 315 billion pounds of plastic in the oceans right now.

Now, Wilson will be the first to admit a lot of assumptions were made in order to arrive at that number, but most of them err on the side of caution. It's worth going through his thought process and calculations here.

To help visualize that massive heap of trash, Wilson divides by a "supertanker" -- that is, a giant ship that could theoretically sail through the seas, skimming out the plastic junk as it goes (much of which hovers down to 90 feet below the surface).

No such ship has been outfitted to skim plastic. But let's say it did, and it could hold 500 million pounds of plastic. You'd need 630 of them to do the job (143 billion kilograms), or about 17 percent of the planet's current fleet of oil tankers.

To make it a little more personal, every American produces about 600 pounds of garbage each year. The proportion of plastic varies from household to household, but overall about half of all waste is synthetic. Some of that probably ends up in landfill, or recycled (Wilson says only about 3 percent of virgin plastic gets recycled).

Either way, the pile of plastic you inadvertently dump into the ocean each year is probably more than you can lift.

The point of the calculations is this: cleaning up the plastics in the ocean ain't gonna happen. Well-intentioned programs designed to take the fight to the high seas, like Project Kaisei and the Environmental Cleanup Coalition, for example, are exercises in futility.

"I'm not trying to call them out," Wilson told Discovery News. "What I really fear is a barge full of plastic coming in under the Golden Gate bridge, the media taking pictures and people thinking 'oh good, we've solved that problem.'"

A real cleanup would be astronomically expensive, both in terms of dollars and equipment.

But hope is not lost. Wilson added that if we can ratchet down the amount of plastic we throw away, the gyres will naturally spin out much of the junk floating in them. Eventually it will wash ashore, where it can easily be removed.

"I really want to see people's efforts focused on beach cleanups," he said. "They're free, can be organized in a grassroots way, and they can make a massive difference. A hundred people on a beach picking up plastic for a weekend can clean up as much as a barge can hold."

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