6 Ethylene

Gallucci

Ethylene is a key building block for many of the chemicals that go into everyday items, including diapers and detergent, fabrics and foams, mattresses and milk jugs, plastic bags, PVC pipes and even airplane wings. It is the most-used primary petrochemical in the world, accounting for about one-third of the industry’s global consumption.

Today, making ethylene involves ​“cracking” apart the molecules in ethane or other hydrocarbons, which is done by burning huge amounts of fossil gas to heat giant furnaces to scorching temperatures. This step alone is responsible for 90 percent of the CO2 emissions associated with ethylene plants.

At Chemelot, near the city of Geleen, the engineering firm Coolbrook is piloting a new kind of technology — one that uses only electricity to crack ethane. The European company recently began testing its electric-driven ethylene reactor, as part of a broader 12-million-euro ($12.7 million) initiative for decarbonizing industrial emissions. In September, Coolbrook successfully completed its first phase of large-scale testing at the site, using an electric heater that makes high-temperature process heat for chemical, cement and steel manufacturing.

Globally, ethylene production totals around 160 million metric tons per year, resulting in more than 260 million metric tons of annual CO2 emissions. That’s roughly the climate equivalent of operating 70 U.S. coal-fired power plants for one year.

The e-cracker concept is steadily gaining traction within the $5 trillion global chemical industry.

The push to electrify ethylene production is a critical step toward reducing the climate impacts of chemical manufacturing, which accounts for about 15 percent of global industrial CO2 emissions every year. But e-crackers can’t address the inconvenient reality that, in its current form, ethylene is fundamentally problematic for the environment.

First, ethane is primarily derived from fossil gas extraction or as a byproduct of petroleum refining. The fossil-based feedstock accounts for about one-third of ethylene’s total life-cycle emissions when measured from the point of raw material extraction to the stage when ethylene leaves the production plant, according to a 2020 analysis commissioned by the American Chemistry Council.

Second, in addition to generating CO2 emissions, the process of cracking ethane gas releases significant amounts of cancer-causing air pollutants, including benzene, butadiene and naphthalene. A 2021 ProPublica investigation found that, across the United States, emissions from two dozen BASF-owned ethylene plants exposed an estimated 1.5 million Americans to elevated cancer risks.

Ethane or other gaseous feedstocks are first mixed with steam inside a ​“turbomachine,” a type of technology also used in jet engines and gas turbines. By spinning a rotor shaft at supersonic velocity, then slowing it down, Coolbrook’s machine converts electrical energy into mechanical energy, then into thermal energy, which directly heats gas inside the reactor — reaching temperatures above 1,830°F (1,000°C). This creates the conditions needed to crack molecules to make ethylene. The concept dates back to at least the 1990s, when a team of rocket engineers began exploring using turbomachines to generate high-temperature process heat for making petrochemicals. Ethylene reactor can yield up to 20 percent more of the chemical when compared to traditional crackers that burn fossil gas to generate heat.

Even if ethylene crackers were equipped to the hilt with pollution controls and were only made using non-fossil feedstocks, that still wouldn’t solve the third and perhaps biggest problem associated with the chemical’s production: Plastics made from ethylene and other ingredients are clogging the world’s waterways at unprecedented levels. Toxic chemicals from plastics are increasingly entering water supplies and our bloodstreams. Unless countries drastically curb consumption, annual plastic use is projected to nearly double by 2050.

The multilayered challenge of tackling an industry that’s both highly polluting and integral to modern society. There’s no simple trick for cleaning up ethylene.

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