The Electric Weed-Zapper Renaissance

IEEE Spectrum

In the 1890s, U.S. railroad companies struggled with what remains a problem for railroads across the world: weeds. The solution that 19th-century railroad engineers devised made use of a then-new technology—high-voltage electricity, which they discovered could zap troublesome vegetation overgrowing their tracks. Somewhat later, the people in charge of maintaining tracks turned using fire instead. But the approach to weed control that they and countless others ultimately adopted was applying chemical herbicides, which were easier to manage and more effective.

The use of herbicides, whether on railroad rights of way, agricultural fields, or suburban gardens, later raised health concerns, though. More than 100,000 people in the United States, for example, have claimed that Monsanto’s Roundup weed killer caused them to get cancer—claims that Bayer, which now owns Monsanto, is trying hard of late to settle.

Meanwhile, more and more places are banning the use of Roundup and similar glyphosate herbicides. Currently, half of all U.S. states have legal restrictions in place that limit the use of such chemical weed killers. Such restrictions are also in place in 19 other countries, including Austria, which banned the chemical in 2019, and Germany, which will be phasing it out by 2023. So, it’s no wonder that the concept of using electricity to kill weeds is undergoing a renaissance.

Actually, the idea never really died. A U.S. company called Lasco has been selling electric weed-killing equipment for decades. More recently, another U.S. company has been marketing this technology under the name “The Weed Zapper.” But the most interesting developments along these lines are in Europe, where electric weed control seems to be gaining real traction.

One company trying to replace herbicides with electricity is RootWave, based in the U.K. Andrew Diprose, RootWave’s CEO, is the son of Michael Diprose, who spent much of his career as a researcher at the University of Sheffield studying ways to control weeds with electricity.

Electricity, the younger Diprose explains, boasts some key benefits over other non-chemical forms of weed control, which include using hot water, steam, and mechanical extraction. In particular, electric weed control doesn’t require any water. It’s also considerably more energy efficient than using steam, which requires an order of magnitude more fuel. And unlike mechanical means, electric weed killing is also consistent with modern “no till” agricultural practices. What’s more, Diprose asserts, the cost is now comparable with chemical herbicides.

Unlike the electric weed-killing gear that’s long been sold in the United States, RootWave’s equipment runs at tens of kilohertz—a much higher frequency than the power mains. This brings two advantages. For one, it makes the equipment lighter, because the transformers required to raise the voltage to weed-zapping levels (thousands of volts) can be much smaller. It also makes the equipment safer, because higher frequencies pose less of a threat of electrocution. Should you accidentally touch a live electrode “you will get a burn,” says Diprose, but there is much less of a threat of causing cardiac arrest than there would be with a system that operated at 50 or 60 hertz.

RootWave has two systems, a hand-carried one operating at 5 kilowatts and a 20-kilowatt version carried by a tractor. The company is currently collaborating with various industrial partners, including another U.K. startup called Small Robot Company, which plans to outfit an agricultural robot for automated weed killing with electricity.

And RootWave isn’t the only European company trying to revive this old idea. Netherlands-based CNH Industrial is also promoting electric weed control with a tractor-mounted system it has dubbed “XPower.” Like RootWave’s tractor-mounted system, the electrodes are swept over a field at a prescribed height, killing the weeds that poke up higher than the crop to be preserved.

Of the many advantages CNH touts for its weed-electrocution system (which presumably applies to all such systems, ever since the 1890s) is “No specific resistance expectable.” I should certainly hope not. But I do think that a more apropos wording here, for something that destroys weeds by placing them in a high-voltage electrical circuit, might be a phrase that both Star Trek fans and electrical engineers could better appreciate: “Resistance is futile.


Source: IEEE Spectrum

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