Weeding with a Laser, an observation in the field

The first thing you notice is a box of light. In fact, it’s the only thing you see when Carbon Robotics’ LaserWeeder gets to work. There’s no movement, no clicking, clattering, or hissing sounds. As you get closer, you might notice small puffs of smoke rising from beneath the machine. Occasionally, you‘ll see red dots lighting up on the ground. All that abundant light you see is just that – light. It’s the laser beams doing all the work. Unlike a laser show at a music festival, you can’t see these beams, but they precisely target the small weeds, essentially bringing them to a boil.

_{Text continues below picture}

The LaserWeeder isn’t a substitute for a hoeing implement but rather serves its purpose where hoeing isn’t feasible for weed control. We observed the machine in action in a spinach field, but apart from broadly planted crops, the LaserWeeder can also replace a lot of manual labor in closely spaced row crops like onions, leeks, or carrots.

The LaserWeeder has only been on the commercial market since last year, with 47 units in operation so far, all in North America.

Cells burst, proteins coagulate

It gets truly spectacular as the twilight or darkness sets in. It’s like witnessing a UFO landing: a powerful white light constantly flashing at a high frequency and synchronized with the cameras beneath the machine to maintain consistent lighting conditions. It’s four times stronger than sunlight. Smoke and small flames might suggest a fire, but it’s not a weed burner, although the principle is similar. The laser light heats the water inside the plant, causing cells to burst, proteins to coagulate, and the plant to wither away. While it might not be immediately evident with smaller plants, the LaserWeeder manages to target almost all weeds.

Pure high-tech

The principle of the LaserWeeder is simple: a camera identifies the plants, a laser focuses a beam of light that is directed at the plant and kills it. The explanation is straightforward, but the technology that makes it happen is pure high-tech. The LaserWeeder is equipped with two rows of cameras. The first row ‘sees’ the plants, and the software marks which ones are weeds. The second row of cameras ensures precise targeting of the laser beam.

The machine boasts 30 lasers across a width of 6 meters, with a total capacity of up to 200,000 plants treated per hour. While a weed growing under the leaves of a crop may escape treatment, if the camera detects it, the laser can hit it. Seedlings are recognized effortlessly, even if they‘re just a millimeter away from the crop plant.

_{Text continues below picture}

The smaller, the faster

The smaller the weed, the more effective the treatment, and the faster the LaserWeeder can operate. Larger weeds require the laser to be directed at them for a longer period to kill them. Longer treatment and higher weed density result in slower operation. Typically, the laser treats a weed for 0.1 seconds. The computer calculates the time required to kill each weed.

The software also counts the crop plants and can decide to eliminate a double-seeded plant. It also keeps track of the weeds, reproducing their location and identifying the type of weed. This generates a significant amount of data.

Equivalent to 24 Teslas under the hood

The computing power required to operate efficiently, especially for speed and numerous calculations, is impressive. According to Carbon Robotics, the server’s capacity on the machine is equivalent to that of 24 Teslas or a computer you‘d expect to find at a top university or research institution like NASA.

A simple fan, as in a regular computer, isn’t sufficient for cooling. Instead, a full-fledged air conditioning system is installed on the machine to prevent overheating. There’s also a chiller, a water cooling tower, to cool the laser tubes. An auxiliary unit is attached to the front hitch for driving the cooling system. The tractor must consistently deliver about 100 hp to power everything. During the demonstration, the onboard computer on the tractor indicated an average fuel consumption of 18 liters of diesel per hour for the entire operation.

_{Text continues below picture}

The LaserWeeder examines each plant, and based on the programming, the computer decides which ones to eliminate. This technology is particularly suited for early-stage weed control. According to American experience, with a 6-meter working width, the machine’s average capacity is approximately 0.6 hectares per hour. The maximum speed depends on the weed density and size but can reach up to 3.5 kilometers per hour.

The laser can also be adjusted for row treatment in crops where inter-row weeding is practiced. When the laser focuses on rows, the speed can be increased compared to full-field operation.

_{Text continues below picture}

Nearly maintenance-free

The LaserWeeder is almost maintenance-free. The lasers require a revision after 2,000 operating hours (equivalent to about 3,500 running hours), a service that Carbon Robotics performs in-house. Assessing the profitability of the LaserWeeder is straightforward: compare the work it does with the next best alternative and do the math.