At our latest CleanStart Perspectives event, we sat down with William McCarthy to hear a raw, honest, and inspiring account of launching a clean tech startup—one that didn’t end in headlines or a big acquisition, but in real lessons that every entrepreneur can learn from.

William started Dunville Sail Bags in 2020, turning used sailboat sails and marine textiles into rugged, stylish bags. What began as a creative upcycling idea in a garage quickly became a full-time hustle: building supply chains from scratch, cutting and sewing in-house, attending over 50 live events, and recovering more than 10,000 pounds of waste.

Despite gaining traction with customers and even Red Bull, William faced the hard truth of running a sustainable product company in a tough market: inconsistent materials, high production costs, and razor-thin margins. After four years of relentless work, he made the difficult decision to close the company, but not without leaving a lasting impact and taking away powerful insights.

Here are some of the takeaways from William’s journey:

• Customer traction was key. In-person sales events brought in both revenue and new supply connections.

• Sustainability alone doesn’t sell. The product had to stand on its own for quality and design, then sustainability became the bonus.

• Scaling with waste materials is hard. Inconsistent inputs made automation and outsourcing nearly impossible.

• You can’t make up for margin with volume. Labor costs and logistics limited profitability.

• Sustainable businesses must also sustain their founders. Mission-driven work is powerful, but it has to pencil out personally too.

Now in Sacramento, William is pivoting to focus on large-scale climate solutions and pursuing a mechanical engineering degree. His message to fellow founders? “Don’t be afraid to close the door on one idea—especially if it leads to the next opportunity. You’ll come out more equipped than ever.”

Thank you, William, for your vulnerability and honesty. Stories like yours are essential for the clean tech community. For anyone building something new: you’re not alone. CleanStart and our community are here to support your journey—successes, stumbles, and everything in between.