Plastic bags in Canada are made from natural gas
In Canada, almost all plastic packaging including plastic shopping bags are made from natural gas; a waste strand of natural gas called ethane. Polyethylene bags are made from a by-product of the natural gas refining process when a strand of the natural gas, ethane, is burned off to lower the BTU/energy value of the gas so it doesn’t burn too hot when used as fuel in our homes and businesses.
Plastic Shopping Bags are actually pieces of frozen natural gas and help conserve the resource during the natural gas refining process.
Ethane is extracted to lower the BTU value of the gas in order to meet pipeline and gas utility specifications. The ethane is converted, and its BTU value is “frozen” into a solid form (polyethylene) using a catalytic process to make a plastic shopping bag.
Bags were invented to help the environment
There is a great deal of misinformation about plastic shopping bags, particularly when it comes to the environment. Plastic shopping bags were introduced in the late 1970’s as an alternative to paper grocery bags, to protect our forests from the needless cutting of trees.
Trees are the Lungs of Life
The use of plastic shopping bags, which are 100% recyclable, eliminates the need to cut down trees to make paper grocery bags. People forget the important role that trees play as the “lungs of the planet” soaking up carbon dioxide and expelling oxygen. On an average a mature tree that is 50 years old produces near about 260 pounds of oxygen in one year. 
They have an environmental purpose. Every scientific study that has ever been undertaken proves that plastic shopping bags have a much lower carbon footprint than paper bags and paper bags are one of the worst options environmentally because of their higher carbon footprint.