Just as I claimed there are no giant steps in sight in the development of forest machinery, something turned up …

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AirForestry is a new Swedish start-up company whose idea is to cut trees with a drone. The drone itself has a diameter of 6,2 meters (19 ft). It will have its own harvester head that delimbs the tree from the top down to the root where it cuts and lifts the tree out of the forest.

This is a summary of an article signed Fredrik Reuter at iSkogen.se

Thinning with a drone

Thinning forest from the air is not completely new. It´s done by helicopter and has been so for decades. But doing it with a drone is something completely new. If it succeeds to go commercial it will have a good potential to become the giant step that I asked for in the last article here at Forestry.com. Battery powered = “fossil free” cutting, all the way to the landing. It´s even politically correct.

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Thinning with a drone

Olle Gelin, one of the founders at AirForestry during a field test of the harvester head.
Photo: AirForestry

Testing with the drone starts in 2022

AirForestry, that was started by, among others, Olle Gelin, former at Skogforsk, has chosen to release the news about the “drone-harvester” quite late. The harvester head has already been tested and a full-scale prototype of the drone is being built right now. Testing of the complete machine in the forest will start in 2022.

Apart from Olle Gelin the company is run by Markus Romer, Mauritz Andersson and Caroline Walerud. When we reached Olle on the phone he explained that the team possesses good knowledge in forestry, drones and digital technology with autonomy.

Thinning with a drone

A full-scale drone is being built right now at AirForestry in Uppsala, Sweden.
Photo: AirForestry

How is thinning by drone done?

The idea of the concept is that you transport the folded drone(-s), batteries and harvester head(-s) to the thinning site on a normal car trailer. The weight of one drone will only be 80 kg (176 lb.) so can easily be transported with a normal car and with a normal driver’s license.

At the landing the drone(-s) is started up and sent to the thinning site. Initially ground staff will be needed to mark the trees that should be cut. The idea however is that also this should be done autonomous in the future.

When a tree is chosen, the harvester head is attached to the top and delimbs the tree downward as the drone is hovering above. When the harvester head reaches the root, it cuts the tree, and the drone lifts the whole tree straight up and takes it to the landing.

At the landing the tree is cut to lengths by the harvester head and put in piles. CTL (Cut-To-Length) is the conventional method in Sweden (and other places) today. But AirForestry sees the possibility to use full tree handling also here in the future, especially for the pulp industry.

When the tree has been processed the drone heads for the forest again to get the next tree. If batteries must be replaced that is also being done at the landing.

Can drones improve thinning?

Already today the drones could be equipped with technology for recognition, coordination and cameras. So, it should be able to do an adapted thinning for each type of stand. Add to that that you don´t need any strip roads, which means a minimum of stem damages on the left trees, and that all slash is left in the forest, and you will have the “perfect thinning”.

Theoretically the drone can carry data for each site so that it can take out exactly the right number of stems to achieve the optimal growth in the stand after the thinning.

Thinning can take place at night, in rain, snow and up to a wind speed of 10 meters per second (22 mi/h).

The production rate compared to conventional methods

The first AirForestry prototype is being built right now. Therefore it´s difficult to say how many cubic meters per hour the drone harvester will produce. The analyzes that have been done, shows that the production rate will be at least as good as with a conventional system with harvester and forwarder. This because the drone always can take the closest route, the bird path, to the landing.

Thinning with a drone

The first drone under construction. Impressive diameter of 6,2 meter and a weight off 80 kg.
Photo: AirForestry

There are also problematic trees, like multi top hardwood trees, that could slow the production down in thinning. But also here AirForestry has a solution as the harvester head can cut in different angles. You could say that the drone can work like an arborist felling difficult trees bit by bit.

According to Olle Gelin, the system will be adapted for first commercial thinning with an average stem size of 0,06 cubic meters under bark. The harvester can however handle stems of twice that size.

Side effects with a thinning drone

Apart from that the outtake could be made optimal and that there will be close to no ground or stem damages in the stand, the presence of a drone means that the stand could be properly surveyed simultaneously with the thinning operation. During the operation you can scan the stand before, during and after the thinning has been done. This will give the forest owner a very good picture of the stand.

As the drone is battery powered, meaning you can call the operation “fossil free”, the system will gain many benefits in today’s climate focused World. One might think that some big forest companies should be interested in investing in such a technology. It should be like a wet dream to claim that your felling operations are fossil free! But no, no forest industry is involved in this project. Maybe it´s because the drone sticks to the recommended outtake, the outtake that is optimized for future growth? (And not to take out as much as possible today)

Anyway, this is exciting. We will follow this even if a commercial drone harvester probably is far away. It´s wonderful to see that someone can think so far outside the box and just don’t care about what the machines have looked like since the 70’s.

This could very well be the next giant step that I asked for.

Read more about the project at AirForestry’s home-page.