Natural Gas And Plastic: What's The Connection?

Plastic is predominantly made from petrochemical raw materials, such as coal, crude oil, and natural gas. Natural gas, composed mainly of methane, has been a booming energy source for the past 15 years, and its use has helped to reduce carbon emissions in the United States. While the majority of natural gas is used for electricity generation, heating, and cooking, a small percentage is converted into the chemicals that make plastics. The process of converting natural gas into plastic is called cracking, where ethane molecules are heated to high temperatures to form ethylene, which is then converted into polyethylene, a common type of plastic.

Natural gas is the raw material for plastic extrusion

The first step in processing natural gas into plastic is the cracker plant. The cracker plant turns either naphtha, a crude oil-based product, or ethane, a natural gas liquid, into ethylene. Ethylene is a gas derived from natural gas or from a fraction of crude oil with a similar composition to natural gas. It is a starting point for a variety of chemical products, including plastic.

The process of turning ethane into ethylene is called cracking because heat energy is used to break apart or crack molecules to form new ones. At cracking temperature, ethane (C2H6) molecules lose two hydrogen molecules, which split off to form a separate, stable hydrogen molecule (H2). This leaves molecules that are about 80% ethylene (C2H4). The ethylene formed in the cracking process is then transported by pipeline to another facility to be converted into usable ethane cracking products. The most common of these products is polyethylene, a resin. At this point, ethylene is still a gas and needs pressure and a catalyst to turn it into polyethylene. The process by which polyethylene is made from ethylene is known as polymerization.

Polymerization occurs when a chemical reaction causes molecules to react together to form polymer chains. These chains can be engineered to control the specific physical properties of the resulting plastic resin, allowing the product to be designed for many different uses. For example, polyethylene can be labelled as low-density or high-density (LDPE or HDPE). These labels can be seen at the bottom of household containers.

The vast majority of plastic in use today is synthetic, derived from the processing of crude oil and natural gas. This is because of the ease of manufacturing methods. However, the growing demand for limited oil reserves is driving a need for newer plastics from renewable resources.

Petrochemicals, including plastic, account for 14% of oil use

Plastic is made from oil and gas, and their byproducts. Natural gas is the raw material for plastic extrusion. Crude oil is a source of raw material (feedstock) for making plastics, but it is not the major source of feedstock for plastics production in the United States. The U.S. Energy Information Administration (EIA) is unable to determine the specific amounts or origins of the feedstocks that are used to manufacture plastics in the United States. However, petrochemical feedstock naphtha and other oils refined from crude oil are used as feedstocks for petrochemical crackers that produce the basic building blocks for making plastics.

Petrochemicals, the category that includes plastic, account for 14% of oil use. The International Energy Agency (IEA) predicts that petrochemicals will be the largest driver of net oil demand growth through 2030 and nearly half of the growth from 2030 to 2050. The World Economic Forum predicts that plastic production will double in the next 20 years.

The demand for plastic is increasing, and companies like ExxonMobil, Shell, and Saudi Aramco are ramping up their output of plastic. This is because, with the world trying to shift away from fossil fuels, oil and gas companies are investing heavily in boosting petrochemical operations to make up for lost fuel demand. The American fracking boom is unearthing large amounts of the plastic feedstock ethane, making the United States a big growth area for plastic production.

However, the current rate of expansion of virgin plastic production is unsustainable. Many organizations have stated that improved waste management and recycling policies will not be sufficient to stem the global tide of plastic waste, and absolute demand reduction is necessary. Many countries have already enacted legislation banning or restricting some single-use plastic products.

Plastic production causes major greenhouse gas emissions

Plastic is made from oil and natural gas, and their byproducts. Natural gas is the raw material for plastic extrusion. Ethane, a byproduct of natural gas drilling, is particularly important in plastic production. It undergoes a series of processes, including cracking and polymerization, to become polyethylene, the most common plastic.

The production and afterlife of plastic are major sources of greenhouse gas emissions. In 2015, emissions from manufacturing ethylene, the building block for polyethylene plastics, were 184.3 to 213 million metric tons of carbon dioxide equivalent. This is about as much as 45 million passenger vehicles emit in a year. The World Economic Forum predicts that plastic production will double in the next 20 years. If this happens, plastic production and incineration are expected to increase greenhouse gas emissions to 49 million metric tons by 2030 and 91 million metric tons by 2050.

The life cycle of plastic generates heat-trapping gases at every stage. The extraction and transport of fossil fuels to create plastic produce significant greenhouse gases. Ethane cracking, which turns ethane into ethylene, requires enormous amounts of power and has a large greenhouse gas footprint. The manufacture of plastic is both energy-intensive and emissions-intensive, producing significant emissions through the cracking of alkanes into olefins, the polymerization and plasticization of olefins into plastic resins, and other chemical refining processes.

The OECD estimates that the life-cycle emissions of plastics, including production and disposal, were 1.8 billion tons of carbon dioxide equivalents. Most of these emissions come from the production stage. If plastic production and use grow as currently planned, these emissions could reach 1.34 gigatons per year by 2030. By 2050, the cumulation of these emissions could reach over 56 gigatons, or 10-13% of the entire remaining carbon budget.

Ethane is separated from methane, the main component of natural gas

Natural gas is the raw material for plastic extrusion. It is composed of about 90% methane, with other heavier alkanes like ethane, propane, and butane also present. Ethane is a crucial feedstock for the petrochemical industry, which includes the production of plastics.

Another technique for separating methane and ethane is gas hydrate formation. This process involves forming crystalline, ice-like compounds called gas hydrates, in which individual gas molecules are caged inside a network of water molecules. By manipulating the conditions such as temperature, pressure, and gas composition, it is possible to selectively form gas hydrates of either methane or ethane, thus achieving their separation. This technique has been experimentally studied and has shown promising results for separating methane-ethane mixtures.

Additionally, the fracking boom in the United States has resulted in the increased availability of ethane as a byproduct of natural gas drilling. With low natural gas prices, producers are motivated to find alternative uses for ethane, making it a valuable feedstock for the plastics industry. This has led to significant investments in plastic and chemical projects, with companies seeking to monetize ethane by converting it into ethylene, a crucial building block for various plastics.

In conclusion, ethane is a critical component of natural gas that serves as a feedstock for the petrochemical industry, including plastic production. The separation of ethane from methane, the major constituent of natural gas, is achieved through various techniques, including selective adsorption, membrane separation, and gas hydrate formation. These processes enable the purification of methane for cleaner energy applications and provide a valuable feedstock for plastic production, contributing to the growing demand for plastics and the utilization of natural gas byproducts.

Ethylene is converted to polyethylene, a common plastic

Natural gas is a raw material for plastic extrusion. One of the byproducts of natural gas drilling is ethane, which is used as feedstock for the petrochemical industry. The process of converting ethane into ethylene is called "cracking" because it involves using heat energy to break apart or crack molecules to form new ones. In this process, ethane (C2H6) molecules lose two hydrogen molecules, which split off to form a separate, stable hydrogen molecule (H2), leaving molecules that are about 80% ethylene (C2H4).

Ethylene is then transported by pipeline to another facility where it is converted into ethane cracking products, the most common of which is polyethylene. This process, known as polymerization, involves turning ethylene from a gas into a resin using pressure and a catalyst. Polyethylene is the world's most important plastic, with over 80 million tons manufactured annually, accounting for over 60% of the ethene produced each year.

There are three main forms of polyethylene: low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE). LDPE and LLDPE are preferred for film packaging and electrical insulation, while HDPE is used for blow-moulded containers, industrial packaging, and piping.

The production of plastic from natural gas has significant environmental implications. The energy-intensive nature of oil and gas extraction, combined with the large amounts of power required for ethane cracking, contribute to a substantial greenhouse gas footprint. As a result, global emissions linked to plastic have reached nearly 900 million tons of carbon dioxide equivalent annually and are projected to increase further.

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