Isolation of ammonium bicarbonate by reactive distillation of food waste digestate liquor

Abstract

Distillation is among the best techniques for management of ammoniacal nitrogen in anaerobic digestate; however, the suitability of the conventional system is neglected in favor of using more advanced setups. This investigation proves the reliability of the classical batch distillation apparatus for high throughput separation of solid crystals of ammonium bicarbonate from food waste digestate (FWD) liquor. Three replicates were carried out: 80 g of FWD liquor with a content of 50 g/L NH₄HCO₃ was processed for 7.5 h under minimum heating power (<60 °C) and 200 rpm to avoid excessive foam formation. After performing the reactive distillation, 81 % of NH₄HCO₃ was recovered as white solid crystals at the top of the distillation still. Although the distillation provided a solid material with the same structure and composition as those of the reagent-grade NH₄HCO₃, the stability of the isolated inorganic fertilizer was poorer, and it could lead to pollution swapping.

Keywords: Chemical stability; Commercial-grade fertilizer; Crystallization; Desorption-absorption; Manure management; Mitigation technology.