With his left hand he holds on to the rope, with his right he aims the banner, which has the word “Demands” emblazoned on it in large green letters.

Secured by a climbing harness, Wolfgang Ertel dangles at a dizzy height.

Ertel is a professor of artificial intelligence, the image of the professor hanging in the tree went through the media last year.

It has now been around ten months since the professor planted trees on his university campus.

The protest action was preceded by around ten years of unsuccessful improvement efforts, says the university teacher.

Specifically, he was concerned with “the banal topic of wasting heating energy”.

He discovered by chance that all lecture halls at Ravensburg-Weingarten University of Applied Sciences are heated during the semester breaks – even when the windows are open.

When asked, the technical operation informed him that the caretakers were so overloaded that they could not switch off the heating manually during the holidays.

As a technician, the idea of ​​an automated controller then came to his mind, says the professor.

In detail, this involved heating at least 118 rooms – 31 large lecture halls, 18 seminar rooms and 69 laboratories.

Wolfgang Ertel estimates CO2 emissions of around 1000 tons per year.

That corresponds to an annual output of 200 to 400 single-family homes.

With an efficient heating system, around 200 tons of CO2 could be saved annually, says the computer scientist.

Automated control of the heating would also be financially worthwhile for the university.

The attempt to install such a system at his university led the university teacher through various authorities for years without success.

"I've actually gone through all the levels in the hierarchy of official channels and tried to do something there and was unsuccessful for over ten years," says Ertel.

In a statement by the German Rectors’ Conference in 2018, the universities were even urged to develop a “culture of sustainability”.

Sustainability rankings are not that easy

For Joachim Müller from the company HIS-HE, what Ertel experienced is not unusual.

With his company, Müller supports universities as an external institution in change processes.

"Universities are very specific institutions," says Müller.

He is not surprised that introducing an automated heating system in Ravensburg is such a lengthy process.

But there are also examples in which such changes have worked much faster.

At its core, it is always about moving actors out of old patterns, which can sometimes be very tiring for those involved, says Müller.

For him, the first hurdle on the way to more sustainability begins with different understandings of the term.

"Everyone talks about it, everyone thinks they know what it is, and afterwards it turns out: we were all talking about something else."

There are rankings that try to grade the commitment of universities in terms of sustainability using uniform rating systems and standardized point systems.

For example, in 2021, 956 universities from 80 countries took part in the “UI Green-Metric World University Ranking”, a sustainability ranking by the University of Indonesia (UI).

German universities are also represented.

But measuring and evaluating a university's commitment to sustainability can sometimes be very difficult, says Müller.

The differences between the various institutions are enormous.

According to this, universities, for example, in which a lot is learned and worked with books, have a lower energy consumption than those that operate experimental reactors and large data centers simply because of their research focus.

Joachim Müller is critical of such a quantitative comparison of universities, as in the case of the green metric ranking.

"Behind every number there is a background." A qualitative description of the commitment to sustainability is more effective in order to be able to do justice to the diversity of the university landscape.