Energy, Climate, Environment

What's Plastic Got to do With Climate Change?

We hardly ever think about how something as simple as a plastic bottle or plastic bag can play a bigger role in our world beyond the convenience for which it was intended. Let's take a look at plastics in our environment. We are inundated with plastics.

Because our existence depends on our planet and its climate, it is important to understand how what we do and the choices we make impacts the Earth. Below are the facts about CO ₂ emissions during the lifetime of plastic bags and plastic bottles that will be helpful for students to know as they engage in the unit's activities.

As of 2008, 70 percent of the synthetic industry was comprised of plastic. Plastic is made from oil and natural gas. Petroleum is drilled and transported to a refinery, involving the release of greenhouse gases into the atmosphere. It is a mixture of various kinds of molecules that are easily separated. The molecules in petroleum are made from two kinds of atoms, carbon (C) and hydrogen (H). A common type of molecule in petroleum is called hexane. Scientists believe the hexane molecule is a string of Hydrogen atoms bonded to the four bonding points of Carbon. Carbon is a particularly useful atom for building molecules because it has four bonding points. Crude oil and natural gas are refined into ethane, propane, hundreds of other petrochemical products and vehicle fuel. Ethane and propane are "cracked" into ethylene and propylene, using high temperature-furnaces that give off heat. A catalyst is combined with the ethylene and propylene in a reactor, resulting in "fluff" which is a powdered material or polymer that resembles laundry detergent. The polymer is fed to an extruder where it is melted. Melted plastic is cooled then fed to a pelletizer that cuts the product into very small pellets. ²⁹ These pellets also find their way into our oceans contributing to the massive amounts of plastic waste swirling around in the Gyres.

Polymers are chains of molecules made up of many units. Each link is usually made up of carbon, hydrogen, oxygen and/or silicon. To make the chain many links are hooked or polymerized together. To create polymers, petroleum and other products are heated under controlled conditions and broken down into smaller molecules called monomers that are the building blocks for polymers. Different combinations of monomers produce plastic resins with different characteristics, such as strength or molding capability.

Between 1997 and 2005, the annual sales of bottles of water holding less than one liter increased from 4 billion to approximately 30 billion bottles. When giving consideration to the energy used for pumping, processing, transporting and refrigerating bottled water the annual fossil fuel footprint calculated for bottled water consumption in the United States is equivalent to more than 50 million barrels of oil. There is no information regarding ingredients on the labeling of plastic products or packaging. The American Plastics Council estimated that somewhere around 5 percent of all plastics manufactured are recycled. Today, most recycled polyethylene bottles are exported to China. China is now the largest destination for plastic waste. When we consider recycling, we should also consider what is involved in the recycling process. In addition to the combustion of fossil fuels required during the recycling process there is the issue of collecting and transporting the recyclable materials to the recycling plant. All of these steps contribute to CO ₂ emissions into the atmosphere. ³⁰

The production of plastic requires huge machinery, lots of fuel and large amounts of energy involved in drilling to acquire the oil and transporting it to refining facilities where fuels and plastics are produced. Electricity is the main source of energy needed to make plastic. The electric energy needed in the production and manufacturing processes of plastic usually comes from coal-burning power plants. ³¹ It is important to keep this in mind when attempting to assign numbers for the calculation of CO ₂ emissions of plastic bags and plastic bottles during their lifetime. The carbon footprint of plastic (LDPE or PET, polyethylene) is about 6 kg CO ₂ per kg of plastic. Take the weight of your plastic bags or bottles, multiply it by the number of plastic bags or bottles you use [per year]. Then calculate the carbon dioxide emitted by your own usage of plastic bags or bottles.

The production of 1 kg of polyethylene (PET or LDPE) requires the equivalent of 2 kg of oil for energy and raw material. Polyethylene PE is the most commonly used plastic for plastic bags. Burning 1 kg of oil creates about 3 kg of carbon dioxide. So, for every 1 kg of plastic (which requires 2 kg of oil), about 6 kg carbon dioxide is created during production and incineration (because burning 1 kg of oil creates 3 kg of CO ₂).

A plastic bag has a weight in the range of approximately 8g to 60g depending upon its size and thickness. According to estimates provided, a common plastic carrying bag weighs between 25 g and 40 g, the average weight being 32.5 g. To simplify the calculation, take the above 1 to 6 relation between kg plastics and kg of carbon dioxide, and you get 195 g carbon dioxide for 32.5 g of plastic, which is the equivalent of the average plastic carrying bag in the household evaluated. So the calculation for 5 plastic bags would be as follows:

5 (plastic bags) X 32.5 g (avg. weight) = 162.5 g of plastic

162.5 g of plastic X = 975 g of CO ₂. ³²

One million plastic bags are used every minute around the world. Over 100 billion plastic bags are used in the United States annually. The total cost of these bags is approximately $ 4 billion. In the U.S. less than 5 percent of plastic bags are recycled and only 1 percent of plastic bags are recycled worldwide.

So, the question to ponder is can something as simple as plastic in its many forms, but focusing on plastic bags and plastic water bottles, contribute to the problems we are experiencing today? Is its contribution significant enough for us to consider making different choices? Is it significant enough to promote alternatives to petro-based plastics? Is it significant enough to care at all? What we want to consider is that the rise in surface temperature, that has already taken place, is going to have irreversible effects on the Earth. The actions we take from this point on, knowing what has happened, can only serve to mitigate the consequences of global warming and climate change by reducing our contributions to CO ₂ emissions into the atmosphere. According to Auden Schendler, "cutting CO ₂ emissions is difficult . . . because we live in an energy-based society." ^{3 3}