In our founder interview series, we skip the slide decks and dive into the sparks, doubts, and pivots that shape early-stage ventures.
Meet Karolin Maiwald and Julian Faust, co-founders of BOIDEL, a Germany-wide deposit system that swaps single-use grocery bags for durable, returnable totes and keeps them in circulation, not landfill.
Karolin brings a “make it work, make it last” ethos. For her, sustainability must be simple, affordable, and for everyone. Julian brings eight years across product design, logistics, and UX – and a lifelong bias toward repairing and rebuilding. Together, they’re turning everyday shopping into an effortless climate action loop: retailers issue a sturdy bag for a small deposit, customers return it, and BOIDEL handles collection, washing, and redelivery.
In this short interview, Karolin and Julian share how BOIDEL’s origin story started in a kitchen, the team-first way they build, the “startup/unicorn/AI” buzzwords they resist (they’re proud zebras), the superpowers they lean on, and the very real “oh sh*t” moments – 200k bags, 18-ton trucks, and spinning up a wash facility in four weeks.
How did you meet?
Through work.
Why start Boidel?
Karolin: Well, I think we both knew that we wanted to create something together. I remember that Julian and I had this conversation, when we saw the problem while sitting in the kitchen. Seeing the deliveries come in and always wondering “why are there so many paper bags?!“
Julian: When Karolyn appeared with this idea, it was a happy day!
How did you divide execution and roles?
Karolin: It was really a team effort from day one. We discussed a lot.
Julian: We tried to build something that we would feel it’s all of our baby. It was really a ping pong game, pivoting a lot, talking a lot. And this is until today.
We speak about everything. We we discuss everything. It prolongs some decisions, but, we can say that we stand behind everything 200%.
What about advice you what to share with other founders?
Julian: Be a team. Be really a team and not just work together. And it comes to such small details.
Karolin: Be open to fears and and talk about them. Create this safe space for each other, apart from work.
Your founder super-powers?
Julian: I would say as a team, we understand each other’s problems without explaining too much. That’s the superpower I never saw in another team.
Karolin: I think your superpower is also, just pushing through and keep going. Really keep going!
Julian: And you know a lot from the top of your head about the business, and you can pitch very well in front of people.
Most over-used startup word right now
Julian: Startup. No, really, this word doesn’t mean anything! Also, unicorn! But we are proud to be zebras.
Karolin: And AI?
Julian: AI is the second or the, I don’t know, tenth buzzword! Yeah!
Describe your co-founder in one word
Karolin: Persistent.
Julian: Better half.
Weirdest / funniest moments while building?
Julian: For me, it was when I had to go to Brazil, and I was working at 04:00 in the morning in a garden.
Biggest “oh sh*t” moment?
Julian: I think one of my biggest oh shit was when we realized the the amount of bags that we have to fit in a truck. What was it? 18 tons? The amount was something around 200,000 bags. So, and three times a week to drive this amount of bags through the city. Since then I have the most of respect for truck drivers.
Another moment is when we were talking to REWE and they told us we have six weeks to set things up. We didn’t have a room, we didn’t have a washing machine, so we had six weeks to build everything, to get every machinery into the workspace.
Karolin: To find a workspace to begin with! We thought we had one, and then we went there, checked it out, and there was nothing. And then we had to run again to find this space we ended up with. We were lucky with this one!
Julian: But REWE came, and said they were impressed with us!