More than 25,000kg of plastic littered in NZ daily

New Zealand, one of 192 countries examined, generated about 3.68kg of waste per person each day. Photo / Thinkstock

More than 25,000kg of plastic waste is littered in New Zealand each day - and each of us mismanages seven grams of it daily.

That's according to the newly-published findings of a global study which estimates between five and 13 million tonnes of plastic waste wind up in the world's oceans every year.

Unless the international community improved its waste management practices, found the authors behind the study in leading journal Science, that number could increase tenfold within the next decade.

The authors found the coastal countries they studied generated about 275 million tonnes of plastic waste in 2010, and that 4.8 to 12.7 million tonnes of that waste entered the world's oceans.

New Zealand, one of 192 countries examined, generated about 3.68kg of waste per person each day - a rate much higher than the vast amount of nations studied.

Nationally, this added up to about 14,212,006kg of waste generated each day, according to the study authors, of the University of Georgia's National Center for Ecological Analysis and Synthesis.

Of that, 1,272,006kg was plastic - contributing to 9 per cent of the total waste stream - and in 2010, 9,286 tonnes of plastic waste was considered mismanaged.
By 2025, that amount would rise to 11,517 tonnes.

The study's lead author, Assistant Professor Jenna Jambeck, used eight millions of tonnes as a midpoint figure to explain the amount of plastic moving from land to ocean each year across the world.

"Eight million metric tonnes is the equivalent to finding five grocery bags full of plastic on every foot of coastline in the 192 countries we examined."

Although plastic pollution in the ocean was first reported in the scientific literature in the early 1970s, until this study, there had since been no rigorous estimates of the amount and origin of plastic debris making its way into the marine environment.

With between 4.8 and 12.7 million metric tonnes going in, researchers were are only finding between 6,350 and 245,000 metric tonnes floating on the ocean's surface.

"This paper gives us a sense of just how much we're missing," co-author and Research Professor Kara Lavender Law said, "how much we need to find in the ocean to get to the total.

"Right now, we're mainly collecting numbers on plastic that floats. There is a lot of plastic sitting on the bottom of the ocean and on beaches worldwide."

The study forecast that the cumulative impact to the oceans would equal 155 million metric tonnes by a decade's time, although the planet was not predicted to reach global "peak waste" before 2100, according to World Bank calculations.

"We're being overwhelmed by our waste," Assistant Professor Jambeck said.

"But our framework allows us to also examine mitigation strategies like improving global solid waste management and reducing plastic in the waste stream.

"Potential solutions will need to coordinate local and global efforts."