American Geological Institute's coverage of Petroleum and the Environment Part 17 indicates that Oil and natural gas are complex mixtures of chemicals. Oil refineries and gas processing plants extract the organic compounds that make the best fuels for transportation, heating, and electricity generation: gasoline, jet fuel, diesel fuel, heating oil, and methane. Other chemicals derived from processing oil and natural gas are called petrochemicals and are used to make thousands of non-fuel products. Getting from Oil and Gas to Petrochemicals Petrochemicals can be produced by refining oil or processing natural gas; petrochemical plants are typically built to use either oil- or gas-derived materials (or both), depending on the availability and price of each. Globally, most petrochemicals are derived from oil, but in the U.S., most petrochemicals are produced from natural gas, due largely to high domestic natural gas production.
The most important raw materials for petrochemicals produced from natural gas are ethane and propane. After methane (which is mostly used for fuel), ethane and propane are the most common organic compounds in natural gas. They are removed during natural gas processing, so the more gas produced, the more ethane and propane are available to make petrochemicals. Ethane and propane molecules are larger and heavier than methane, so they require less pressurization or cooling to turn them into liquids, earning them the name “natural gas liquids.” During gas processing, other natural gas liquids are also derived in smaller amounts and are processed and used for many purposes, while methane itself is used as a source of hydrogen to make fertilizer and other products (see below). Naphtha, a liquid mixture distilled from crude oil at refineries, is also used as feedstock for various petrochemicals. Ethane, propane, or naphtha can be heated to very high temperatures (up to around 850 °C, or 1562 °F) to break apart molecules (“cracking”) or selectively pluck hydrogen atoms off the molecules (“dehydrogenation”) to form new chemicals such as ethylene and propylene.
Ethylene and propylene are the two dominant petrochemicals: in 2016, the U.S. produced over 26 million tons of ethylene and over 14 million tons of propylene. Ethylene is primarily converted into polyethylene (the most common plastic, used in thousands of applications), but is also used to make other plastics such as polyvinylchloride (PVC, for pipes and home siding) and polystyrene (used as a general plastic and as Styrofoam for insulation and packaging). Propylene is mostly converted into polypropylene for fibers, carpets, and hard plastic; some propylene produced during oil refining is used to make compounds that are added to gasoline to improve performance. Both ethylene and propylene are used to make many other chemicals and materials with many uses, including specialty plastics, detergents, solvents, lubricants, pharmaceuticals, synthetic rubbers, and more.
From Petrochemicals to Consumer Products
Most plastics, synthetic fibers (such as polyester and nylon), and resins (such as epoxy) are produced from petrochemicals. These products are major components of vehicles, home and office buildings, electronics, clothing, packaging, and more. While these are some of the best-known uses of petrochemicals, other major uses of petrochemicals and other non-fuel products of oil and gas include:
• Fertilizers – hydrogen derived from methane (the main ingredient in natural gas) is combined at high temperatures with nitrogen extracted from air to make almost all of the ammonia in the world (a small amount of ammonia is produced using other sources of hydrogen such as propane, naphtha, or gasified coal). About 88% of U.S. ammonia consumption is used as the nitrogen source for fertilizer. Other important uses of ammonia include household and industrial cleaning products, refrigerants, and in the manufacturing of plastics, dyes and explosives.
• Pharmaceuticals – almost all pharmaceuticals are made from chemical feedstocks manufactured from petrochemicals and their derivatives.
• Many detergents and other cleaning products are made from petrochemicals. Similar cleaning products made from plant oils are now widely available, although these products are often also produced using substances made from petrochemicals.
• Road asphalt consists of roughly 95% crushed stone, sand, and gravel; the remaining 5% is a thick, dark oil known as asphalt or bitumen, which occurs naturally in some rocks but is also produced by oil refining.
Fertilizer: Ammonia from Natural Gas
Ammonia, a compound of hydrogen and nitrogen, is industrially produced on a vast scale. The U.S. produced over 10 million tons of ammonia in 2017,7 almost entirely using hydrogen derived from natural gas. Roughly 88% of this ammonia is used to provide nitrogen for fertilizer, making up almost 60% of all fertilizer used in the United States. With growing domestic natural gas production, low natural gas prices, and new fertilizer plants coming online,11 U.S. ammonia production capacity is expected to grow by 25% from 2018 to 2022. Over this same period, global ammonia production (150 million tons in 2017) is expected to grow by 8%.
Medicine: Plastics and Pharmaceuticals
Plastics are so widely used that it is easy to forget how varied they are – the most common plastic, polyethylene, comes in 10,000 different types for different uses.12 In medicine, plastics serve a wide variety of purposes: keeping medical equipment sterile; providing inexpensive disposable syringes, tubing, and single-use supplies to reduce the risk of infection; and forming implants and artificial joints, as well as many advanced materials, including natural-synthetic hybrids that can be used inside the body with lower risk of rejection.
Petrochemicals and the Environment
When oil, gas, and the environment are discussed together, the focus is often on the ways in which oil and gas can damage environmental or human health, and steps that can be taken to prevent or reduce these impacts. Petrochemicals are an interesting case because they have both positive and negative impacts on the environment. The negative impacts are significant and should not be understated, but they are also generally well-known: the accumulation of plastic waste, the harm that plastics and their breakdown products can cause when ingested by animals, and the damage to aquatic ecosystems caused by fertilizer runoff (caused by both natural and petrochemical fertilizers). The environmentally beneficial uses of petrochemicals are less commonly discussed but are an important part of any discussion of overall environmental impacts. Some of these environmentally beneficial uses include:
• Oil absorbents used to clean up oil spills.28 Natural biological materials (e.g., feathers or straw) can absorb 3-15 times their weight in oil, while minerals (e.g., sand and vermiculite clay) can absorb 4-20 times their weight in oil. These natural materials are inexpensive but they can often sink in water, making them less effective for oil spills at sea. Synthetic oil absorbents made from plastic or nylon can absorb up to 70 times their weight in oil while staying afloat, making them effective for oil spill cleanup in water.
• Federal regulations require construction or demolition sites to have barriers that prevent stormwater runoff from carrying sediment and waste into sewers, rivers, or streams. These barriers are often made of plastics or synthetic fibers, which are weather-resistant and impermeable.
• Some petrochemical-derived products can be used to remove carbon dioxide from the combustion gases of power plants, thus reducing the greenhouse gas emissions of energy production. In 2017, the Petra Nova project near Houston, Texas, began operations as the largest such project in the world.
The above is only selected topics of interest in a larger document. Read the full document.
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