Abstract
For feeding the world in 2100, the global agriculture, the entire food chain, as well as the behavior of all consumers must be change fundamentally. Essential resources needed to intensify agriculture and use barren land, such as phosphorus, water, and fossil fuels, are becoming increasingly scarce and expensive. An ecological form of agriculture that uses these resources more responsibly requires more land for the same yields. Therefore, new concepts for food and feed production have to be developed, in which nutrients are recycled beyond these areas. A possible starting point could be bioreactors, since these are enormously efficient and enable resource-efficient land use. Wastewater treatment as a means of nutrient recycling will be one of the most important tasks in the future. Hereby, not only the heterotrophic bioreactors currently used for this purpose but also autotrophic photobioreactors show great potential, especially if these two reactor types would be combined. Because of the ability to use inorganic nitrogen and phosphorus for their growth as well as the ability to produce a wide range of metabolites, microalgae offer an integrated approach. This review provides an overview of the potential of microalgae as components of a sustainable, circular agricultural system for feed and food production.