History
Plastic bags are often made from polyethylene, which consists of long chains of ethylene monomers. Ethylene is derived from natural gas and petroleum.
Patent applications relating to the production of plastic shopping bags can be found dating back to the early 1950s in the United States and Europe, but these refer to composite constructions with handles fixed to the bag in a secondary manufacturing process.
The lightweight shopping bag as we know it today is the invention of Swedish engineer Sten Gustaf Thulin. He developed the idea for forming a simple one-piece bag by folding, welding and die-cutting a flat tube of plastic in the early 1960s for packaging company Celloplast of Norrköping, Sweden. His idea produced a simple, strong bag with a high load carrying capacity and was patented worldwide by Celloplast in 1965.
Celloplast was a well established producer of cellulose film and a pioneer in plastics processing. The company's patent position gave it a virtual monopoly on plastic shopping bag production and the company set up manufacturing plants across Europe and in the US. However, other companies saw the attraction of the bag, too, and US petrochemicals group Mobil overturned the Celloplast US patent in 1977. TheDixie Bag Company of College Park, Georgia, owned and operated by Jack W. McBride ("The Bagman") was one of the first companies to exploit this new opportunity to bring convenient products to all major shopping stores. McBride's Dixie Bag Company, as well as Houston Poly Bag and Capitol Poly were instrumental in the manufacturing, marketing and perfecting of this bag by the early 1980s. Kroger, a Cincinnati based grocery chain, agreed to try this innovation. So, the real change in grocery bags did not start until 1982, when two of America’s largest grocery companies Safeway and Kroger started replacing paper bags with more affordable plastic bags.
Without its plastic bag monopoly, Celloplast's business went into decline, and the company was split up during the 1990s. The Norrköping site remains a plastics production site, however, and is now the headquarters of Miljösäck, Sweden’s largest producer of waste sacks manufactured from recycled polyethylene.
From the mid 1980s on, the use of plastic bags became common for carrying daily groceries from the store to vehicles and homes. As plastic bags increasingly replaced paper bags, and as other plastic materials and products replaced glass, metal, stone, timber and other materials, a packaging materials war erupted with plastic shopping bags at the center of highly publicized battles. Currently, while no peer reviewed study or government survey has provided estimates for global plastic bag use, environmental activists estimate that between 500 billion and 1 trillion plastic bags are used each year worldwide. In 2009 the United States International Trade Commission did report that the number of bags used in the Untied States was 102 Billion.
Manufacture and composition
Plastic shopping bags are commonly manufactured by blown film extrusion.
Plastic shopping bags are usually made of polyethylene. This can be low-density, resin identification code 4, or most often high-density, resin identification code 2. Most plastic bags are derived from natural gas.
Biodegradable materials
Although not in use today, plastic shopping bags could be made from Polylactic acid (PLA) a biodegradable polymer derived from lactic acid. This is one form of vegetable-based bioplastic. Bags can also be made from degradable polyethylene film. Most degradable bags do not readily decompose in a sealed landfill and represent a possible contaminant to plastic recycling operations.
Environmental concerns
Each year millions of discarded plastic shopping bags end up as litter in the environment when improperly disposed of. The same properties that have made plastic bags so commercially successful and ubiquitous—namely their low weight and resistance to degradation—have also contributed to their proliferation in the environment. Due to their durability, plastic bags can take up to 1,000 years to decompose.As they slowly decompose, plastic bags break into tiny pieces and leech toxic chemicals into soils, lakes, rivers, and oceans.
On land, plastic bags are one of the most prevalent types of litter in inhabited areas, becoming an eyesore to local residents. At their worst, plastic bags can clog drainage systems and contribute to flooding, as occurred in Bangladesh in 1988 and 1998. When plastic bags are washed out to sea, they pose a threat to animal life. In the decades since plastic bags first came into wide use, there has been a dramatic increase in the quantity of plastic bags found floating in oceans around the world. Once in the ocean, these bags can strangle wildlife or, if ingested, can choke or cause wildlife to starve to death. Many marine species, including sea turtles, seals, sea lions, manatees, whales and dolphins have been killed as a result of ingestion of plastic marine litter, including plastic bags.
Littering is often a bigger problem in developing countries, where trash collection infrastructure is less developed, than in developed nations, however once plastic bags are swept out to sea they can travel long distances in ocean currents.
Reuse and recycling
Heavy duty plastic shopping bags are suitable for reuse as reusable shopping bags. Lighter weight bags are often reused as bin bags (trash bags) or to pick up pet faeces. All types of plastic shopping bag can be recycled into new bags where effective collection schemes exist.
Since internet rumours started to claim that the Environmental Protection Agency had reported only 1% of plastic bags were recycled, significant attention resulted in a 700% growth in the recycling industry as new capacity led to a 7% rate. This resulted in more than 800 million lbs of bags and other film being recycled in 2007 alone. Each ton of recycled plastic bags saves the energy equivalent of 11 barrels of oil, although most bags are produced from natural gas derived stock. In light of an Australian study showing more than 60% of bags are reused as bin liners and for other purposes, the 7% recycling rate account for 17.5% of bags available for recycling.
Bag legislation
Bans
Plastic bags are either restricted or completely banned in more than 25 percent of the world. Belgium, Italy, Ireland and Hong Kong have legislation discouraging the use and encouraging the recycling of plastic bags by imposing a fixed or minimum levy for the supply of plastic bags or obliging retailers to recycle. In other jurisdictions, including three states and territories of Australia, Bangladesh, South Africa and Thailand, plastic bags are banned. In the United States bans were imposed on local level, starting with San Francisco in 2007, followed by other jurisdictions including Los Angeles County in 2010. Similar bans on municipality level were imposed in India, Mexico and UK.
Taxes
The plastic bag levy introduced in Ireland in 2002, resulted in a reduction of over 90% in the issuing of plastic bags. The "ban on free plastic bags" in China introduced in 2008 resulted in a reduction by two thirds. In the United States, the five-cent tax levied on plastic bags in Washington, DC in 2010 resulted in a decrease in consumption from 22.5 million to 3 million bags in the first month alone.
Recycling
Many states and cities in the United States have approached bag litter and landfill with a more practical approach in recycling laws such as California, New York, Chicago, Delaware, Baltimore , and many other cities and states.
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