COLUMN // ENERGY
The Electric State
Plasmas, the underappreciated fourth state of matter, might well be a platform technology for a sustainable future.
Written by Michael E. Webber
Any of us with children or grandchildren on the cusp of adulthood wrestle with the compulsion to take them aside and impart crucial bits of wisdom that will set them on the straight path to success. It’s an impulse so strong and longstanding that it’s been skewered by William Shakespeare in Hamlet and by Calder Willingham and Buck Henry in their screenplay for The Graduate.
“One word,” says the character of Mr. McGuire to young, befuddled Benjamin in that movie. “Plastics.”
In all honesty, looking into plastics wasn’t bad advice in 1967. Today, better advice would be to get into a different type of matter: Plasmas.
Plasma sounds science-fiction-y, but they are found in lightning in the sky, cutting torches at construction sites, and home appliances such as flat screen televisions. Basically, plasmas form at really high temperatures when materials move beyond a gaseous state to one where electrons are liberated from atomic nuclei, enabling the free electrons and free positive ions to conduct electricity and interact with magnetic fields at a distance.
This handy feature opens the door for a variety of innovative processes that can replace relatively dirty conventional sources of heat with cleaner processes driven by electricity. A familiar application was in fluorescent light bulbs, which use electricity to produce a low-pressure mercury plasma. These bulbs helped achieve national energy conservation goals after the oil crises of the 1970s and then reduced electricity consumption again in the 2000s when they began to replace incandescent bulbs for home lighting.
Granted, these applications of plasma are hardly new. But from my perch as a research professor, former CTO at a multi-billion-dollar cleantech venture fund, and retired research executive at one of the world’s largest energy companies, plasmas are popping up on my radar with increasing frequency and for a wide range of new and exciting applications. For instance, startups like 6K in North Andover, Mass., are proposing to use plasmas to replace dirtier, heat-based processes to fabricate battery materials domestically. And a recent life-cycle assessment review shows that gasifying solid wastes into useful energy via plasmas is a vastly superior approach to waste management compared with landfilling or incineration.
“There is one potential application for plasmas that would be utterly world-changing: fusion reactors to produce electricity.”
A potentially exciting application of plasmas is the production of hydrogen, which today is often manufactured via steam methane reforming, a relatively affordable process that releases a lot of carbon dioxide into the atmosphere. Some entrepreneurs have looked to add carbon dioxide capture systems to the fabrication process (and then sequester the CO), but these additional steps are expensive and require a lot of space and equipment.
Instead, plasma pyrolysis can be used to liberate the hydrogen atoms from the methane, generating a solid carbon powder that is easier to handle than gaseous CO₂. At the very least, the solid carbon can be easily landfilled, but even better, it can be used to make graphite, which is a critical ingredient for modern batteries that further accelerate the energy transition. That carbon is also a building block for graphene, water filters, and soil amendment.
Plasmas can clean up other industrial processes. They can convert carbon dioxide to carbon monoxide at steel mills, lowering emissions of the flue gases while improving output because the CO is used in the iron ore reduction process. And California startup Nitricity—a clever name that combines nitrogen and electricity—uses plasma to make fertilizers at the farms that need them, using only air, water, and almond shells as inputs; their method avoids the CO₂ emissions not only of conventional ammonia factories but also of the large diesel-powered tanker trucks that move ammonia from centralized factories to farms.
Aerospace is also showing greater interest in plasma. Ion thrusters (those ions are a plasma) have long been prized for their great efficiency for long-duration space missions. But research suggests that plasma actuators can replace expensive and fragile moving parts on aircraft wings, improving cost and flight efficiency in the process.
Now, all the uses listed above are of great interest and offer one alluring benefit or another. But there is one potential application for plasmas that would be utterly world-changing: fusion reactors to produce electricity. Fusion requires temperatures measured in the tens of millions of degrees to provide hydrogen or other nuclei enough speed to overcome atomic forces that repel them, allowing the ions to fuse together, releasing heat in the process that can be used to generate power. The temperatures needed for fusion are so high that electrons can’t stay bound to their nuclei; by definition, fusion needs plasmas.
The sun gives us the ultimate proof of concept for fusion as a power source, but it has the convenience of using its own mass and immense gravity to confine its plasma. On Earth, our power plants need to be somewhat smaller, so engineers and physicists generally look to magnetic fields to confine and compress the plasmas. Fusion can generate essentially unlimited clean power without dangerous waste products, greenhouse gases, meltdown risks, or worrisome weapons proliferation, all of which are great outcomes for a plasma system.
Taken together, this wide range of applications has inspired me to tell my 19-year-old son, a sophomore mechanical engineering student, to look at a career in the field of plasmas. Though he gives me the same befuddled look as Benjamin from The Graduate when I give unsolicited suggestions, I believe it’s advice that will hold up.
MICHAEL E. WEBBER is the Sid Richardson Chair in Public Affairs, John J. McKetta Centennial Energy Chair in Engineering, and engineering academic director of the KBH Energy Center at the University of Texas at Austin.
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