铝罐还是塑料瓶？

The bottled water industry is increasing efforts to replace plastic bottles with more easily recycled aluminum containers, or cans. The effort follows public anger about reports that plastic water bottles are severely polluting the world's oceans.

The French Danone company is the latest to replace some plastic water bottles with aluminum cans. Competitors like Coca-Cola, PepsiCo and Nestle have also started selling water in aluminum cans.

Replacing plastic water bottles that pollute the seas with recyclable aluminum cans should be an easy way to help the environment, right?

Maybe not.

Aluminum cans might result in less ocean waste, but they also come with their own cost to the environment. The production of an aluminum can is estimated to release two times as much carbon dioxide into the air as a plastic bottle.

"That's the dilemma you're going to have to choose between," said Ruben Griffioen, an official at beermaker Heineken. He said his company was trying to reduce both plastic waste and carbon dioxide release.

The Environmental Protection Agency says aluminum cans have about 68 percent recycled content compared to just 3 percent for plastic bottles in the United States. As a result, aluminum is widely seen as the better choice for the environment.

Martin Barrow is with the non-profit organization Carbon Trust. He said, "The aluminum industry can play on the fact that its product is infinitely recyclable, and they're right."

However, Barrow said, "aluminum uses huge amounts of electricity and it's also got some chemical releases of greenhouse gas emissions."

Never be that clean

Aluminum has a larger carbon footprint in production because of the power needed in the smelting process. But, the metal containers also are lighter than glass or plastic bottles. Also, aluminum cans require less electric power to cool the liquid they contain.

"It's a complex picture," said Simon Lowden of Pepsico. "You have to think about transport, secondary packaging, time in store, all those considerations come into play."

Bruce Karas of Coca-Cola North America agreed. He said, "There's a mix, there are some things that are not that desirable, but if you have five good things and one that isn't, we'll all have to make decisions."

"It'll never be that clean," he added.

Plastic strikes back

Bottled water is a $19 billion industry. Although its use of cans is increasing, experts say cans are unlikely to completely replace plastic bottles.

Aluminum is costlier than plastic so canned drinks mean higher prices for buyers. Another major consideration is user convenience – cans stay open while bottles can be reclosed.

Karas said Coca-Cola is still looking at how the buying public reacts to canned water. The company plans to test the market. Later this year, it will carry out a limited launch of its water product, Dasani, in aluminum cans and aluminum bottles that can be reclosed.

Other companies, including Danone and Pepsi, are testing new plastics that are biodegradable or easier to recycle.

There is another possible barrier to ending the use of plastic water bottles: There may not be enough cans to go around. Beer and wine makers are now also increasingly using aluminum.

An official with Ball, the world's top supplier of aluminum cans, said, "This is a level of growth that we haven't seen in a long time."

I'm Jonathan Evans.

Hai Do adapted this story for Learning English from a Reuters news report. Caty Weaver was the editor.