Paper or plastic? It depends

Which bag is best for the environment?

Paper or plastic? Does that familiar choice in the grocery line really matter for purposes of green living?

Yes, it does. But maybe not the way you think.

Paper bags, for example, take more energy to manufacture than plastic, according to some measures. Yet paper bags are easier to recycle and turn into new bags. Although plastic bags tumbling in the breeze are an eyesore, they’re far cheaper to make.

The list goes on. But by any measure, it’s better to reuse a bag — no matter what kind — than to take a new one, experts say.

And neither type of bag matches the environmental impact of burning gasoline in a car to get to the store in the first place.

For almost every upside paper or plastic bags might have, they also have downsides, according to analyses of the raw material and energy that goes into each bag.

Consider:

Paper bags are made from renewable material — wood. But more energy — some of it generated by coal or natural gas — goes into producing them than plastic bags.

Plastic bags weigh less, so it takes less fuel to haul them around. But they’re also a littering nightmare — catching on trees, floating across the ocean, strangling and choking wildlife.

Paper bags are easily recyclable and biodegradable, but many still end up in the landfill where they are often sealed away and do not biodegrade. If they do degrade, they emit greenhouse gases.

Plastic bags are cheaper upfront. But when people mix them into curbside recycling, they wreak havoc at recycling plants by entangling sorting equipment.

The convenience factor

Plastic has clearly won the bagging battle.

About 80 percent of customers choose plastic, which are often more convenient when walking and sturdier — especially in the rain, said Joe Gilliam, president of the Northwest Grocery Association. By some estimates, 10 plastic bags are used for every paper bag.

Often, though, the lighter and smaller something is, the less energy it takes to make. That holds true for bags and is the main reason it takes less raw material and energy — and produces less air and water pollution — to manufacture lightweight plastic bags than heavier paper sacks, according to most calculations.

“The idea that paper is only made from wood is misleading,” said David Allaway of the Oregon Department of Environmental Quality’s solid waste division. “You may not see it, but fossil fuel goes into making paper, too.”

Ease of recycling

If high numbers of paper shopping bags are recycled, though, it helps tilt the energy balance in paper’s favor because less energy goes into making a recycled bag than a new one. Few plastic bags are thought to be recycled.

Depending on the paper mill, it may take more fossil fuel to make a recycled bag, Allaway said. That’s because many mills use energy from wood byproducts to manufacture new bags.

Plastic-type bags that biodegrade provide another option, promoted in San Francisco as an alternative. But they also have a drawback: If they inadvertently end up with regular plastic bags for recycling, they can ruin the entire batch.

The environmentally friendlier option is to use fewer bags, or reuse them, which saves the energy to make the bags and recycle them. The main advantage of recycling is not so much saving space in the landfill, but saving the energy of producing new items to replace what people throw away.

Many stores now offer reusable shopping bags made from recycled water bottles.

While bags may be visible, Allaway warns that everyday pursuits such as driving your car or heating your home make a far bigger difference.

“The amount of energy here is pretty small,” he said. “It would be tragic if people got twisted in knots over this and didn’t pay attention to the petroleum burned in the engine of their car.”