In this episode of Plan Sea, hosts Anna Madlener and Wil Burns sit down with Stefano Capello, CEO and founder of Limenet — an Italian startup focused on limestone-based ocean alkalinity enhancement (OAE) and net-zero lime production — and Sara Groppelli, a PhD researcher at the University of Milano-Bicocca studying the impact of Limenet’s approach on phytoplankton communities. Stefano discusses Limenet's journey from theoretical experiments in his grandmother’s garage to a pilot plant in Italy that is navigating key, real-world questions around cost efficiency and scale, environmental safety, permits and regulatory pathways, and community engagement.

Stefano recounts Limenet’s unconventional beginnings, which started as a prototype research project in his grandmother’s garage, and now operates a pilot facility in southern Italy. Since 2023, Limenet has focused on developing an OAE approach that pre-dissolves limestone alkalinity in reactors and pre-equilibrates seawater with atmospheric CO2 before releasing it back into the ocean. This closed-system approach is designed to reduce scientific uncertainty in alkalinity additions and to minimize risks such as particle sedimentation or unwanted precipitation.

Now, Limenet is focused on addressing key questions about how its OAE approach could be scaled. Stefano shares updates on the company’s journey to reduce the energy intensity of its lime production and the associated costs, and how the team is engaging communities and policymakers as they navigate Italy’s regulatory landscape. 

The ecological safety of Limenet’s OAE approach are also important to thoroughly evaluate, and Sara shares updates from her research on potential impacts on phytoplankton communities. Sara highlights how controlled alkalinity enhancement appears to have limited ecological disruption when carefully designed. However, long-term and site-specific studies are important to thoroughly understand potential impacts and also co-benefits, such as potential buffering against ocean acidification. 

Listen to the full episode to learn more about Limenet’s growth and how the team is approaching important questions around environmental safety, cost and scale, monitoring and evaluation, community engagement, permitting pathways, and more.

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative and the American University Institute for Responsible Carbon Removal. Subscribe on your preferred podcast platform and find the entire series here.

ACRONYMS/CONCEPTS:

• CDR: carbon dioxide removal
• ISO: International Organization for Standardization
• MRV: monitoring, reporting, and verification
• OAE: ocean alkalinity enhancement

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.