As shipping comes under fire for emitting more pollutants than previously expected, there comes a new twist as another study reveals shipping recycling to China emits less carbon dioxide (CO2) than sending it to a local landfill site.

The emissions caused by transporting material from the UK to China accounted for on average less than a third of the CO2 saved by recycling, according to a study by Waste Reduction Awards Program (WRAP).

The UK recovers more paper for recycling than the paper industry can cope with.  The demand from China, however, which doesn't have enough forestry of its own, remains high, making it the world's largest importer of waste paper, according to a report in the Telegraph.

The same is said of recovered plastic bottles where China acts as a valuable 'sink market' mopping up what the UK cannot cope with, the report added.

"It may seem strange that transporting our unwanted paper and plastic bottles such a distance would actually be better for the environment but that is what the evidence from this study shows.  It is clear that there are significant CO2 savings that can be made by shipping our unwanted paper and plastic to China," said WRAP's chief executive, Liz Goodwin.

Sending one tonne of recovered paper produced between 154kg- 213 kg of CO2 and transporting one tonne of recovered plastic bottles ranged between 158kg-230 kg of CO2.

The transport emissions were significantly less at 10% of the overall amount of CO2 saved by recycling, because the waste is able to travel in containers that would usually be empty because the UK imports more than it exports to China.

"In some cases, we just aren't able to reprocess everything we collect or there isn't enough of it to do so.  In these cases, shipping it to China, which has a high demand and need for material, makes sense in CO2 terms," Goodwin added.

Exports of recovered paper increased from 400,000 tonnes in 1998 to around 4.7m tonnes in 2007 and exports of recovered plastics increased from less than 40,000 tonnes to more than 500,000 in the same period.

China now accounts for more than half of the UK's exports of recovered paper and more than 80% of recovered plastics.