Phosphorus pentoxide production with fluorine management includes collecting phosphorus from kiln off gas as phosphoric acid containing fluorine and reacting the fluorine in the phosphoric acid with reactive silica to yield fluorosilicic acid. The fluorosilicic acid is removed from the collected phosphoric acid. Fluorine management includes discharging from the kiln a residue containing processed agglomerates and heating the discharged, processed agglomerates and releasing fluorine therefrom. The released fluorine is reacted with reactive silica to yield fluorosilicic acid and the fluorosilicic acid is collected. Fluorine management includes forming a reducing kiln bed with feed agglomerates below a reducing freeboard. Kiln off gas is generated containing phosphorus in the form of elemental phosphorus a) oxidized outside of the kiln to phosphorus pentoxide and collected as phosphoric acid, b) collected as elemental phosphorus, or c) both.