Phosphorous acid (H3PO3) and its conjugate base, phosphite (HPO3 2-), have found applications as reducing agents, as the starting material for preparing basic lead phosphite, 1 a stabilizer for chlorine-containing plastics, as cathode materials for lithium-and sodium-ion batteries, as well as the starting material for other commercially important reduced phosphorus compounds, such as glyphosate. Phosphite and related H -phosphonate esters are a family of key intermediates to organophosphorus compounds via elaboration of the P-H function into P-C bonds. Recent advances in biotechnology have also cleared out a path for phosphite to act as an environmentally friendly herbicide, biostimulant, and biocide in modern agriculture owing to its minimal toxicity to humans and animals, biodegradability in soil, and inability to trigger eutrophication of natural water bodies through agricultural runoff. The development of transgenic crops that metabolize phosphite rather than phosphate has allowed phosphite to serve as both fertilizer and herbicide. Additionally, phosphite is thought to have been a potential major nutrient in the pre-oxygenated Archaen oceans. However, current production of phosphorous acid relies on an energy-intensive process known as the thermal process in which the phosphorus in phosphate rock is first reduced at 1500 • C to P(0) (white phosphorus, P4), followed by oxidation back to P(III) as PCl3 using chlorine gas. Subsequent hydrolysis provides phosphorous acid (Figure ). This carbothermal legacy process is very energy intensive and involves substances that are environmentally hazardous. In addition to phosphate rock, the primary source of phosphorus, phosphate recovery from waste streams is becoming an increasingly important method to obtain phosphorus, as phosphorus is a nonrenewable resource 19-21 and high concentrations of phosphate in a water body lead to eutrophication. Among those phosphate recovery methods, one well-established process, known as enhanced biological phosphorus removal (EBPR), utilizes microorganisms to take up phosphate from waste water and store it in intracellular polyphosphate granules. In the "Heatphos Process", polyphosphate can be released from bacteria by heating at 70 • C for 1 hour. The recovered phosphate can be used as a raw material for the fertilizer industry.