Milk protein plays an important role in nutrition, however, milk production has significant environmental impacts, from greenhouse gas (GHG) emissions to extensive land demand. Project HYDROCOW addresses this challenge through a net-zero carbon dairy protein production platform. The main objective of the project is to develop and demonstrate a first-of-a-kind engineered hydrogen oxidizing bacterium (eHOB) Xanthobacter sp. SoF1-based protein secretion system, where CO2 and soon N2 is valorized into food-grade protein, decoupled from agriculture. The main milk component, beta-lactoglobulin was chosen as the first product. Technically this will be achieved by implementing a Design-Build-Test-Learn (DBTL) cycle linked to a validation and scale-up phase allowing to iteratively optimize the production of secreted protein. The project will deliver key technologies – A) an innovative eHOB protein secretion system; B) predictive eHOB metabolic models, genetic engineering tools, and a novel high-throughput (HTP) screening system for DBTL cycling; and C) the methods for validation and scale-up – with immediate and long-term impact on the production of food and nutrition, materials, medicines, fuels, and chemicals. In the long-term, the proposed platform has the potential to not only replace conventionally produced food proteins but also deliver proteins for materials or therapeutics, important for human and animal health. In comparison to current standard microbial production processes our platform does not compete with human nutrition for valuable feedstock, such as glucose, and therefore will contribute to the sustainable development of our society. HYDROCOW will generate significant knowledge for a growing research and application community about autotrophic, microbial production systems, their physiology, and sophisticated tools for genetically designing and screening them.