Which recyclable bags?

Many US shopping chains are now promoting reusable shopping bags and no longer give away free throw-away bags. In some cities, such as San Francisco, the singlet bags are banned in supermarkets and chain stores. It is however proving to be difficult to determine what really is an environmentally responsible bag. Here are some of the concerns:

• Often bags are made in China and shipped thousands of kilometers using unique fossil fuels while polluting the oceans and shores with the exhaust from dirty marine fuel just to get them to the place where they are to be reused
• Often bags are made of plastic which takes a long time to decompose. They can't be washed.
  
• If bags are not reused they are more environmentally damaging than disposable thin bags because they are made with more solid materials.
• Many cheap recyclable bags are made in Chinese factories from polypropylene, using 28 times as much energy as a disposable bag
• Cotton bags can require a large amount of water and energy to produce and may use harsh chemical dyes. However they can be washed and reused for a long time like clothing.
  
• Paper bags destroy trees and the factories pollute water and air. They can be reused many times but usually aren't.
  

The biggest problem is to get people to use reusable bags even after they buy them. But at the same time disposable plastic bags are becoming unpopular. 100 billion plastic bags are thrown away each year in the US.
Producers of reusable bags have reported big increases in sales.