According to the American Chemistry Council (ACC), using plastic bags instead of paper bags provides an excellent opportunity to be a little more green. Not only does the production of plastic bags use 70 percent less energy than the production of paper bags, according to the ACC, the process to recycle 1 lb. of plastic uses 91 percent less energy than that used to recycle 1 lb. of paper.

Plastic bags are essentially films, thin plastic sheets, typically less than 0.2 mm thick. People use four types of polyethylene to make plastic bags usually.

High-Density Polyethylene (HDPE)
The vast majority of grocery store bags are made of HDPE. The shape of them seem to be one plastic shirt from the front side, many people also call them as shirt bag. They are in bule, red, white commonly. HDPE is semi-transparent, easy-to-wrinkle, with a lack of ability to stretch. HDPE bags, identified by recycling code 2, tear easily, but because of their strength, are well-suited for use as grocery bags, bags for clothing and air cushions for packaging. 

Medium-Density Polyethylene (MDPE)
MDPE is clear than HDPE and less semi-transparent than low-density polyethylene. And the impact resistance of it is less than HDPE. MDPE, identified by recycling code 4, is typically used in consumer packaging for paper products such as paper towels and toilet paper.

Low-Density Polyethylene (LDPE)
LDPE is with moderate stretch, strength properties and a high degree of clarity. LDPE, identified by recycling code 4, is commonly used in consumer packaging as bread bags or thick bags for newspapers. Sometimes nylon is incorporated into LDPE to make Bubble Wrap.

Linear Low-Density Polyethylene (LLDPE)
LLDPE is slightly thinner than LDPE with a stretchy consistency. LLDPE films typically feel tacky and exhibit a moderate degree of clarity. LLDPE, normally identified by recycling code 4. is generally used for stretch wrap, dry cleaning film, agricultural films and thin newspaper bags.

Recycling
According to the ACC, 12 percent, more than 830 million lbs., of plastic bags and film was recycled in 2007. Recycled applications for plastic bags include construction and building products and new plastic bags. With the exception of LLDPE used for agricultural purposes, any of these bags can be included in the recycling bin wherever collection bins are labeled for plastic bag recycling.

The ACC recommends that consumers check with their local grocery stores to determine if their stores sponsor plastic bag collection. For consumers looking for municipal drop-off centers, ..........org provides a listing of community recycling programs across the country.