Sustainable Phosphorus

Abstract Phosphorus is a critical element, fulfilling important roles in bio‐, organic‐, and inorganic chemistry. Due to its versatile chemistry, phosphorus‐based chemicals have a wide array of applications in society. Most importantly, phosphorus is an irreplaceable and limiting building block for life. As such, the natural phosphorus cycle has historically set the pace for all life on earth. This all changed with the discovery of phosphorus‐based fertilizer, which has been largely responsible for the spectacular population growth over the previous century. Consequently, society has become highly dependent on these fertilizers for global food security. This comes with two major problems. Phosphate rock, the primary phosphorus resource, is finite and dwindling. While shortages are not imminent, continuation of current practices will eventually make them an inevitability. More pressing, however, is the problem of waste. Much of the phosphorus we use ends up in the environment, which has serious deleterious effects on biodiversity. Anthropogenic activity has thus disrupted the natural phosphorus cycle to such an extent that the word “cycle” is hardly applicable anymore. Clearly, there is pressing need for more sustainable practices. This article provides a holistic view on this important topic. The phosphorus industry relies on two phosphate rock‐processing pathways, based on either elemental white phosphorus or phosphoric acid as primary intermediate. Most fine chemical production relies on white phosphorus, accounting for a few percent of the market. As this process requires high energy investments, it is ideally omitted entirely. Novel synthetic pathways based on phosphoric acid are therefore needed, and notable examples are discussed, more in line with the principles of Green Chemistry. Ideally, chemicals are retained in near‐indefinite closed loops, using waste as resource as advocated by the Circular Economy and Circular Chemistry principles. Hazardous chemicals risking emission to the environment should be substituted where possible, or redesigned to alleviate their potential for harm. The vast majority of phosphate rock is processed to phosphoric acid, easily derivatized, and mostly reserved for the agri‐food sector as fertilizer or animal feed. This sector is highly inefficient, with major losses attributable to agriculture, food production, and consumption, as well as prior mining. Excess phosphorus intake due to animal product consumption exacerbates the problem. To address these issues, an interdisciplinary approach is necessary, involving legislation, education, and international cooperation between the many stakeholders. To truly close the phosphorus cycle, however, phosphorus needs to be recycled from human and animal waste. Many processes based on precipitation, wet and thermochemical treatment have been developed for phosphorus recovery, but value chains are necessary to bridge the gap between recovery and recycling. This requires alignment across stakeholders, favorable economics, and facilitative legislation.