The invention relates to "closed loop" processes, systems and compositions for providing flame retardant properties to substrates containing at least about 5 weight percent of non-thermoplastic material, such as non-thermoplastic fibers, fibrous compositions or fabrics, and to treated substrates. The processes and systems are environmentally friendly, and advantageously conserve chemical compounds and water by recycling flame retardant composition. The processes of the invention generally comprise: (a) applying a flame retardant composition containing one or more flame retardant substances, an aqueous liquid and one or more adhesion agents to substrates; (b) removing excess flame retardant composition from the substrates; (c) permitting the substrates to dry to a low moisture content; and (d) recycling excess flame retardant composition; wherein the flame retardant composition does not contain an amount of a dye or other agent that could contaminate the flame retardant composition. A preferred "closed loop" system of the invention is shown in FIG. 1.