‘Undune’, the unexpected potential of our excreta

There is a treasure that many of us unconsciously waste, a free resource which can help us giving a very personal contribution to the environmental protection: our faeces, a natural cycle product that can have extraordinary effects once back to nature.

Undune’, a documentary directed by Dennis Rätzel that obtained many awards during some of the festivals members of Green Film Network, faces this issue in a very original way. The movie won the Jury’s Prix Special at FReDD, the Jury’s Special Mention at Ecocup and the Honorable Mention by the Júri da Juventude at Cin’Eco in Seia.


‘Undune’ brings back to the attention an ancient technique -created in Amazonia- which can regenerate barren soils and make them permanently fertile with the action of funguses and other life forms. Faeces are one of the fundamental components of this kind of soil.

The topic was just at hand”, told us the director about the genesis of his work. “Gregor Pieplow, the art director and protagonist of Undune, is the son of one of the researchers that rediscovered the Terra Preta method. Gregor was a good friend already before the film production and hence I knew about his father’s work. I wanted to produce a full feature documentary and there was the topic. In the writing process together with Lydia Böttcher, we were able to connect the creation of soil from feces to the biggest endeavors of the 21st; the colonization of Mars – may it be reasonable or unreasonable. This way, the story became even more interesting to Gregor and me also from an artistic perspective”.

Widely underestimated, human excreta are rich in nutrients and can give a unique contribution to solve many environmental issues, beginning with agriculture and food production.

Undune is about the need to reconsider the way we deal with one of our greatest resources; our excreta”, continues Rätzel. “I had the feeling that it was time to tackle this taboo. Worldwide soils are eroding and we are loosing valuable land due to global warming, while the need for foodstuff is increasing. We always tend to think that only our government can solve these problems and sometimes, we feel small and lost. So, people should know about alternative possibilities to contribute to the fight against the greatest threat to humanity of our time. The Terra Preta method to create fertile black soil from our faeces is a particularly direct way of contribution“.

Between reality and fiction, ‘Undune‘ shows Gregor’s experiments to make human excreta usable on Mars. At the same time, the documentary shows how our faeces could change our Planet’s fate, more concretely than we think.

I think film is a great medium to inform the audience about alternative possibilities“, explains the director. “If well made, a film carries us away and we sink into the story or get entranced by its beauty. We become open to possibilities that we may have rejected from the start in a normal discussion. You could call it a medium of agitation if you want. But I see it rather as a positive aspect of film making that you can get people think about ideas that they otherwise may have never considered. There are of course very different ways to do that. In a pure documentary, you try to deliver your version of the truth to the audience and in that process, you deliver them your conclusions in a more or less open way. In a fictional film, your ideas and conclusions are hidden in the story. Fiction can serve as a Trojan horse to the audience’s perception. In Undune, we decided to try and find a path in between the two types of film. However, you can also always create a film just for entertainment or as pure beauty. There is nothing against that”.

With a brilliant and captivating style, Dennis Rätzel’s documentary film teaches us to look things in a different way and to discover new opportunities where we’d never thought we could find them.