How can I pass my PhD thesis defense when nothing has been successful? For reasons I had very little influence on, most of the projects I participated in over the course of my PhD did not produce reasonable results. I managed to get involved in small side projects and publish at least something, but those are not very novel in itself and not "on the edge of knowledge".
The edge of knowledge I pushed is what could go wrong when you are a lone representative of a "service science" in a collaboration, who is asked for input in the beginning, but later overthrown. And in the end, we look at the data together and establish we can't do what we wanted with it. And part of the problem is in fact that my input was not that valued by decision makers.
This take-home message is more of a meta-topic and for sure not the main result of my thesis though.

In my thesis, I will (with a heavy heart) go through those projects and discuss them. Discuss what happened, what we did and what we should have done and could have done. This writing process is a very hard piece of work to do and is taking a toll on me right now. But I am doing it and trying to detach myself from the thoughts of how these failures could end up killing my dreams of an academic career.

In my defense, I am supposed to paint a picture-perfect representation of at least one major project. I don't have any options for this. I got caught in doing small "services" to help my collaborators and starting new projects ("we will do better this time") which always ran into a roadblock (mostly before I even got significantly involved).

I do not want to whine about science in my defense. I do not want to explain what went wrong, to the people who did it sitting in the room with a plan to cheer me through my presentation. But what can I do?
People usually find one "example" of what they did that worked out well and then "blow this up" to be the main point of their defense, while it might only be a small part of the work they did over the years. But I cannot find a single interesting topic with nice results. They are either trivial or failed.

Has anybody done a "fully failed" PhD defense ... and passed? How would one do this?
The specifics here are certainly best discussed with your advisor. They should know about your discipline, and how to frame results in a way that is suitable for the community.


  Has anybody done a "fully failed" PhD defense ... and passed? How would one do this?


For me, it does not sound at all like you "failed" in your PhD. A PhD is a research project, not a product. Ultimately, you (and your committee) should not evaluate your results based on whether they ended up being useful, but based on whether you had a reasonable thesis and a thorough scientific study of this thesis.

That is, if you proposed a novel approach, collected reasonable data, and thoroughly validated your initial thesis, your research was successful, independently of whether this approach then ended up being used in the larger project context. Sure, it would be nice to be able to say that your approach has then helped these other people to do A, B, C, and D, but the real world does not always work like that.

To me, it is mainly a question of mindset. If you yourself consider your PhD "failed" you will have a hard time selling it to a committee. You need to embrace the idea that you did good research, and not measure the success of your own work on factors outside of your control. In that sense, you should defend what you did and why. You can, and maybe should, discuss why it ended up not being used if there are interesting lessons learned, but stay away from political or interpersonal arguments (these can indeed sound whiney). Stay positive and focus on what you did, not on how much other people then liked the results.