To compare multiple wastewater treatment processes associated with recycling or recovery of nutrients, we divided them into three categories: biological, chemical, and physical. Figure shows all 2001-2021 journal/patent publications on wastewater treatment for nutrient recovery using these 3 groups of methods. Figure shows that patents make up a significant part of the publications on chemical and physical methods. More than half of all publications on physical methods (53%) and 49.5% on chemical methods are patents, while the contribution of patents on biological methods is only 37%.