Trawl­ing for plas­tic in the Pa­cific

Sys­tem 001, an in­ge­nious de­vice to clean up the Pa­cific Ocean.

Vocable (All English) - - Sommaire -

On 9 Septem­ber, Sys­tem 001, the flota­tion de­vice put to­gether by the Dutch startup, Ocean Cleanup, be­gan its jour­ney in a se­ries of tests off the coast of Cal­i­for­nia. It marks the begin­ning of a hugely am­bi­tious mis­sion, to clean up the Great Pa­cific Garbage Patch, an im­mense ex­panse of float­ing, mainly plas­tic, refuse on the sur­face of the Pa­cific Ocean, lo­cated be­tween Hawaii and Ja­pan. How does this in­ge­nious sys­tem work?

F ew things ex­er­cise green sen­si­bil­i­ties more these days than marine plas­tic lit­ter. The de­tri­tus looks un­sightly when it washes up on beaches, and cruel when it chokes pho­to­genic sea crea­tures. Sci­en­tists es­ti­mate that per­haps 8m tonnes of plas­tic waste en­ters the ocean each year, dis­charged by rivers or shed from ships. Plenty stays close to shore. Some, though, is car­ried by cur­rents to mid-ocean gyres.

2. The big­gest of these is lo­cated half­way be­tween Cal­i­for­nia and Hawaii—and so lit- tered with flot­sam that it has been nick­named the Great Pa­cific Garbage Patch. A study pub­lished last March in Sci­en­tific Re­ports by Lau­rent LeBre­ton of the Ocean Cleanup, a Dutch char­ity, and col­leagues, found that it con­tains be­tween 45,000 and 129,000 tonnes of plas­tic de­bris spread over an area roughly the size of Alaska.

A CLEVER DE­VICE

3. The idea of sweep­ing it all up might sound fan­ci­ful. To Boyan Slat it seemed merely am­bi­tious. What if, he won­dered in 2012 (then aged 18), you could build a mas­sive bow-shaped float­ing bar­rier, an­chor it to the seabed and let cur­rents shuf­fle the lit­ter into the scoop? De­spite his youth­ful age and mad­cap scheme, Mr Slat set up the Ocean Cleanup to put it into prac­tice. Six years, € 20m ($23m) and sev­eral pro­to­types later, the de­vice set sail from San Fran­cisco on Septem­ber 8th, es­corted by a Coast Guard ves­sel, a shipload of cam­era crews and a flotilla of cu­ri­ous boaters.

4. Sys­tem 001, as the con­trap­tion has been chris­tened, is a hol­low cylin­der 600 me­tres long and 1.2 me­tres in di­am­e­ter, it­self made of plas­tic (poly­eth­yl­ene). It was moulded to­gether into a seam­less whole from 12-me­tre seg­ments at a ship­yard across the San Fran­cisco Bay in Oak­land. A three-me­tre-deep skirt (made of sturdy polyester) dan­gles be­neath the boom to pre­vent lit­ter from es­cap­ing un­der it; buoy­ant plas­tic tends to float within a me­tre of the wa­ter’s sur­face.

5. The de­vice is even sim­pler than Mr Slat’s orig­i­nal idea, hav­ing dis­pensed

with the an­chor. In­stead, it re­lies on the ob­ser­va­tion that the boom, which is driven by the cur­rent as well as by waves and wind, al­ways moves faster rel­a­tive to the plas­tic, which is pro­pelled by the cur­rent alone. It there­fore scoops the lit­ter up as it drifts.

CLEAN­ING THE GREAT PA­CIFIC GARBAGE PATCH

6. A straight boom will first be towed 250 nau­ti­cal miles off the coast of Cal­i­for­nia for a fort­night of tests, be­fore em­bark­ing on a three-week voy­age to its fi­nal des­ti­na­tion. There it will be turned into a U-shape, with its ends fas­tened in place us­ing me­tal lines, and set adrift. Satel­lite track­ing and other elec­tron­ics will al­low its progress to be mon­i­tored re­motely. Light bea­cons will alert the two dozen ships which cross the gyre each week to its pres­ence. Some time next year another ves­sel will be dis­patched to fish out the col­lected rub­bish, which the char­ity hopes to sell to re­cy­clers.

7. If Sys­tem 001 suc­ceeds, Mr Slat wants to de­ploy another 60 booms, mea­sur­ing 1km or more. Cor­po­rate spon­sors would foot the bill of €5m apiece for con­struc­tion and three years’ op­er­a­tion, Mr Slat hopes. He al­ready en­joys the back­ing of deep-pock­eted en­dow­ments and of ty­coons like Marc Ben- ioff, founder of Sales­force, and Peter Thiel, a noted in­vestor.

8. The sys­tem can do lit­tle about plas­tic that has frag­mented into mi­cro­scopic par­ti­cles, but these make up just 8% of plas­tic in the gyre. Mr LeBre­ton reck­ons that a fleet of booms could, by 2040, sweep up vir­tu­ally all the non-tiny de­tri­tus, but only if plas­tic leak­age into the sea is stanched. If it con­tin­ues un­abated, the in­com­ing de­bris would out­weigh the fleet’s ca­pac­ity to skim it within a few years. The ocean’s plas­tic prob­lem can­not re­ally be solved with­out bet­ter waste man­age­ment on land.

If Sys­tem 001 suc­ceeds, Mr Slat wants to de­ploy another 60 booms.

(The Ocean Cleanup)

Sys­tem 001, es­corted by a Coast Guard ves­sel, is be­ing in­stalled at a Pa­cific trial test site on Septem­ber 15th.

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