The climate-related concerns associated with the manufacturing
of synthetic fertilizers are largely traced back to energy and carbon
emissions during the chemical manufacturing of ammonia. However, synthetic
fertilizers are made up of several macronutrients (nitrogen, phosphorus
and potassium), each with different energy intensities and environmental
impacts. With the movement toward resource circularity, there is a
need to create a more holistic view regarding the process energy associated
with synthetic inorganic fertilizers, including nitrogen and phosphorus.
Here, we first describe the growing production and consumption of
inorganic (synthetic) and organic (animal waste) nutrients in agriculture
as well as the process energy associated with the production of granular
phosphorus and nitrogen-based fertilizers. Next, we present projected
global demand of nitrogen and phosphorus nutrients based on various
sustainability and societal equity scenarios to make an argument for
nutrient recovery as a viable approach to meet this demand. Finally,
we discuss the characteristics and challenges of emerging technologies
for nutrient recovery along with baseline performance and costs of
current operational recovery facilities.