Using drones to thin the forest

Mauritz Andersson during a test flight of the 6.2 metre-wide drone. Photo: Private

Why not let drones cut down and remove trees when the forest needs thinning, rather than using heavy, fossil fuel-driven forestry machinery? This would lessen the impact on forests and land, and reduce the climate footprint, according to researchers behind an innovation that is now on its way to becoming a reality.

It really all began with electric aircraft. Mauritz Andersson at the Department of Electrical Engineering was engaged in research on powertrains for electric planes. He started to feel a desire to translate his knowledge into real products that could benefit both people and the environment.

“The climate crisis is a real challenge for us, after all. It’s scary, but also a tremendous driver of innovation. I don’t believe we have ever seen so many inventive people all around us who are actually trying to mitigate the crisis in various ways,” Andersson says.

He found an outlet for his own inventiveness when he met Markus Romar, who ran a startup consultancy, and Olle Gelin, whose background was in forestry research. Together, in 2020, they established the company AirForestry as a means of developing new technology for forest thinning from the air – without traditional forestry machinery.

“Current thinning interventions often have to be carried out in wet conditions, which results in the ground becoming rutted and churned up. For access and to be able to drive machinery, you have to make extraction lanes. On top of that, there’s a risk of smashing roots and damaging other trees that are supposed to remain standing,” Andersson says.

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Without touching the ground

The idea he came up with was to let flying craft do the job instead.

“By lifting it up into the air, we see we can do the job with greater energy efficiency, we can do it without touching the ground at all and we can actually let the trees that are intended to remain standing, remain standing without smashed up roots. We will be able to cope with the first thinning, as it’s called. These are trees that weigh up to 140 kg or thereabouts and have a trunk up to about 22 cm in diameter,” he explains.

The drone they have developed is 6.2 metres wide, battery-driven and equipped with six propellers.

“In a parallel process, we have developed our thinning tool and tested it from a crane to stimulate being with a drone. It thins from above. It lops off branches largely using the downward force of gravity. Of course this also contributes to energy efficiency. And then it cuts through the trunk and holds the tree, and then we will fly out with it. We’re now in an integration phase where the task is to put these two things together and get it to work,” Andersson says.

Completely autonomous

He is now on a leave of absence to work full-time at AirForestry and sees great potential for their innovation. Apart from avoiding damage to the forest and only taking the trees selected for thinning, Andersson believes it will improve forestry workers’ work environment. The drones are intended to be completely autonomous, so the job can be done sitting inside a work shed.

“At the moment, a whole development team is needed to fly a single drone. In future, there will be multiple drones, more than four,” he adds.

Åsa Malmberg

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