Global food systems are highly resource-intensive and yet are unable to meet humanity’s nutritional needs. Given their high levels of productivity, low land and water use, and significant protein and amino acid content, marine microalgae have been considered for animal and aquaculture feeds, along with direct human consumption. In order to determine the potential viability of marine microalgae as an environmentally sustainable feed or food product, I use GIS methods to identify global cultivation potential for marine microalgae in terrestrial raceway ponds based on key environmental inputs: solar radiation, access to seawater, flat land, and nutrients. I then project growth in the global demand for protein-rich foodstuffs and their corresponding emissions—direct (i.e. energy consumption) and indirect (i.e. land use practices). I utilize FAO projections for protein needs by country through 2050 and overlay these data with cradle-to-grave emissions of traditional protein sources. I thus map national, regional, and global lifecycle emissions for major protein sources through mid-century and identify areas with the greatest need for sustainable nutrition by the scale of growth in population and food-based emissions. The result is a high geospatial resolution blueprint for where microalgae can sustainably meet growing food demand as well as advance society’s goals for reducing greenhouse gas emissions. I demonstrate how the mass-production of marine microalgae would be especially advantageous for regions with greatest projected protein demand increases as well as regions that are environmentally-suited for microalgae cultivation. This research has direct implications for near-term development of microalgae farms that can help to fill gaps in sustainable protein production. and refers to existing policies that could further encourage the growth of this technology.