Reimagining Phosphate Fertilizer Production by Circumventing the Wet Process
The dominant current mode of phosphate fertilizer production is via the wet process, in which the key step is the treatment of phosphate rock with concentrated sulfuric acid to generate phosphoric acid. Several factors impede the long-term sustainability of the wet process. First, the sulfuric acid employed in the process is produced via sulfur combustion and the sulfur is sourced from the hydrodesulfurization of petroleum feedstocks. As the world transitions to a reduced reliance on fossil fuels, the supply of plentiful low-cost sulfur may diminish and impose supply chain risks for the wet process. Second, the wet process produces stoichiometric quantities of phosphogypsum waste that poses an environmental hazard. Third, an evolving regulatory landscape may impose more stringent limits on heavy metal impurity levels in the phosphate fertilizer. Since the wet process does not completely remove heavy metal impurities, these regulations may impede the utilization of lower-grade phosphate rock deposits for fertilizer production. These factors motivate efforts to reimagine phosphate fertilizer production in ways that completely circumvent the wet process.
We have identified two complementary pathways for circumventing the wet process that leverage biological and electrochemical processing steps. The biological pathway will utilize microorganisms to absorb and accumulate phosphate from its growth media, which can be derived from phosphate rock through acidity modulation using waste acidic gas like CO2, or from various dispersed phosphate sources. The electrochemical approach will focus on carbon-negative electrosynthesis of phosphorus (P4), as the precursor of various high purity P-chemicals. The electrosynthesis utilizes phosphate rock as its primary input and is compatible with the poly-P produced in the biological stage. We envision that these approaches will enable the production of high-purity phosphoric acid, phosphate fertilizers and other P-chemicals directly from phosphate rock, as well as from various dispersed phosphate sources. By eliminating the need for sulfur and eschewing the production of phosphogypsum waste, these approaches have the potential to radically disrupt the legacy wet process and enable a more sustainable phosphate future.
UM6P Project team
TBD