Oct. 10, 2022, © Leeham News: Batteries are the best thing for the new generation of clean airplanes. Or so say those promoting the concept.
However, few talk about the total life cycle of the concepts, whether eVTOL, hybrid-battery aircraft or pure battery airplanes.
And there’s the rub. Batteries may be clean in operation. But they are far from being a panacea for life-cycle clean aviation.
Some acknowledge that the power source for charging batteries could be an eco-issue. Others acknowledge that recycling batteries is an issue. A few acknowledge that today’s batteries don’t last very long—they must be replaced every 1,000 to 2,000 flights, depending on usage and other factors.
But so far, the real skunk at the lawn party is the fact that mining lithium, a key chemical for long-lasting batteries, is strip-mining, one of the most environmentally damaging methods of extracting anything from the earth.
“When you start evaluating all of these options, you have to actually do what they call a lifecycle assessment,” says Graham Webb, the Chief Sustainability Officer for Pratt & Whitney. “You have to understand all of the environmental implications from the time you’re ripping the raw materials out of the ground until you’re actually disposing of the product at the end of its lifecycle.
“When you do those calculations, you need to see that in the end, you’re doing better than what is your alternatives. In the case of lithium batteries, not all of the lithium is made by strip mining. But China, in particular, a very large supplier of lithium, that is the predominant mode of mineral extraction.”
Webb said that some companies, such as Tesla, are discussing with Texas putting a lithium refinery in an area that enables them to have a bit more vertical control over all the economics. This includes the environmental implications of what they’re doing with their batteries.
“But it’s a challenge and it’s really admitted that all of these, shall we say ‘solutions,’ whether it’s lithium on the battery side, or let’s talk hydrogen, require life cycle assessments,” Webb said. For hydrogen, he added, 95% or more of the hydrogen that’s generated today is made by steam reforming of methane. The lifecycle assessment of those fuels is currently worse than the alternative, which is jet fuel kerosene.
Most of the companies talking about battery-power airplanes, eVTOLs, or Air Mobility Aircraft (AAM) avoid talking about the extraction of the chemicals. They don’t talk about recycling, let alone talking about compliance with Federal Air Regulations. Nor do they talk about batteries having to be replaced after 2,000 flights, and what you do with the batteries you take out.
Either all of these companies that are talking about this stuff without talking about the life cycle are conveniently ignoring the life cycle realities.
Webb is more charitable.
“It could be there’s a little ignorance as well. In some cases,” he said. “They get so focused on the end state of making a battery-powered aircraft fly and considering that to be, shall we say emissions-free, which I’ve heard some of them state. But in the end, it is not just the batteries. Recharging the batteries comes from the grid. The grid isn’t always grained, and in assets, you’ve got emissions that are associated with recharging those batteries.
“They don’t always speak to those implications,” Webb said. “But certainly, people are becoming increasingly aware of those implications and they’re bringing that forward to those folks to make sure that they’re being addressed as part of the overall equation of how these products are coming into the market.”
Some point to hydrogen as the better alternative to batteries. Certainly, as a fuel, it is easier to get the power required for flight from hydrogen than it is from batteries. But there are significant design-integration challenges for an airplane to use hydrogen. And the infrastructure, from production to fueling, is vast.
More to the point for green fuel advocates, hydrogen isn’t a panacea. Research still is needed to understand the impacts of contrails emitted from hydrogen.
“When we start talking about contrails, contrails in terms of the current theory are generated from water vapor and the exhaust of the gas turbine engines,” Webb said. “Kerosene has water, and it makes contrails we’re well aware of that. Hydrogen has 250% more water vapor present in its exhaust. If you start talking about something that has 250% more water vapor, that’s where the concern comes to rise. The other element of where the research needs to be done is how contrails are formed. That’s where the science is lacking.”
Webb continued, “How do you avoid contrails, which some of our scientists are showing that they’re actually equal to, if not worse than, the implications of carbon dioxide from aviation and climate impact? That’s where you see the testing that Airbus is going to be conducting with our competitor’s engine. They’re going to go and determine whether or not hydrogen does generate contrails and what the mechanisms are so that there’s a better understanding. Then, of course, that understanding would drive avoidance or methods to prevent them from forming.”
As air transport is only two to three percent of the total problem, what air transport does do will have little climate impact. Let’s hope the intense focus and research aviation is doing on the subject will benefit more sectors of society. Otherwise the money and resources could be better invested in fields with higher climate impact.