Petrochemicals are chemicals derived from petroleum or natural gas. They are an essential part of the chemical industry as the demand for synthetic materials grows continually and plays a major part in today's economy and society. Petrochemicals are used to manufacture thousands of different products that people use daily, including plastics, medicines, cosmetics, furniture, appliances, electronics, solar power panels, and wind turbines.
It's important to note that the biggest concern about fossil fuel use is from combustion, turning these hydrocarbons into carbon dioxide and water. So while there are environmental concerns about petrochemical manufacturing of plastics, it doesn't lead to a significant release of greenhouse gases that can cause climate change. For example, the plastic manufacturing is capturing the carbon in an inert form (the plastic) and not releasing it to the atmosphere.
Petrochemicals are derived from hydrocarbons such as propane, ethane, butane, or other components separated from crude oil and natural gas liquids. Naphtha - a mixture of flammable liquid hydrocarbons - is also important in the production of products made from petrochemicals. After being separated in some sort of distillation process, separated hydrocarbons can be fed to a manufacturing facility known as a cracker. This cracker works to break chemical bonds in hydrocarbon materials which allows them to be converted into more useful chemicals for production. One major petrochemical is ethylene, used to create polyethylene - one of the most important plastics in manufacturing.
In petrochemical plants, shown in Figure 1, monomers like ethylene are connected to form giant molecules with thousands of carbon atoms known as polymers. These long chains are then transformed into plastics through a variety of molding techniques.
99% of all plastics are created from oil and natural gas, with most being manufactured using naphtha feedstock. Naphtha is created during the distillation process, and is heavier than gasoline. It is one of the most important of all the petrochemicals simply because it is used in the production of plastics. Other important petrochemicals include:
For a more in-depth look at the wide variety of petrochemicals and their uses, see here.
The use of plastics in modern life is extremely widespread, and most products we use today are either made entirely of plastics or have plastic components. These plastics are made by using a variety of petrochemicals and provide us with a variety of goods from single-use saran wrap to components of our cars. Although plastics are used extensively, there are concerns with the sheer volume of plastics being used and disposed of in particular. In addition to the volume of plastic waste, the fact that plastic doesn't biodegrade is an issue. Instead, plastic photodegrades into small bits of plastic known as mermaid tears or nurdles - shown in Figure 2 - that can absorb toxic chemicals. If these nurdles are then ingested, these toxins can then harm the animal. These waste plastics can wind up in landfills or oceans and these small pellets can be easily transported.
A core issue is that although plastics are long-lived products that could be used for many decades, the way they are used now tends to be in single-use items that are disposed of within a year. Once in a landfill, they will remain there for centuries. These plastics accumulate in landfills, and also in the ocean. Currently, there is a large mass of accumulating garbage in the ocean, composed mostly of plastics, known as the Great Pacific Garbage Patch (shown in Figure 3). One common misconception is that large plastic pieces are floating around in this area, when in reality the majority of the waste has broken down into nurdles, which leaves the water looking cloudy and murky. This patch is estimated to be twice the area of Alberta (or twice the size of Texas for Americans).
In addition to the lack of biodegradability and long life, there are several health and environmental effects that can be connected to the disposal of plastics. First, the chemicals added to plastics can be absorbed by human bodies, and some of these compounds have been found to alter hormones and have other potential health effects. If ingested, these plastics can harm humans. This ingestion could occur from drinking water that has been contaminated by chemicals that have leeched out of plastics in landfills. As well as harming humans, plastic debris (whether still intact or broken down into small "pellets") are often ingested by marine animals and can injure or poison wildlife.
For more information on the Great Pacific Garbage Patch, see NOAA's page here.