Innovative Integrated Technique for Nutrient Acquisition: Simultaneous Recovery of Carbon and Nitrogen Sources from the Anaerobic Fermentation Liquid of Food Waste

Anaerobic fermentation liquid from food waste contains abundant nutrients, such as volatile fatty acids (VFAs) and NH3–N, which are promising nutrient sources for plant growth. Here, we report a novel integrated technique for the simultaneous recovery of C and N sources from anaerobic fermentation liquid. VFAs and NH3–N extracted from anaerobic fermentation liquid were synthesized and converted into layered double hydroxides (LDHs) and NH4HCO3, respectively, for subsequent use as soil amendments to provide external C and N to plants. The X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy/energy dispersive X-ray spectroscopy results suggested that VFAs were successfully intercalated within the LDH, and the composite (VFA-LDH) exhibited good sustained release performance. In the VFA-LDH synthesis process, the concentrations of chemical oxygen demand, VFAs, and NH3–N were reduced by 49.4%, 27.9%, and 43.6% in the anaerobic fermentation liquid, respectively. In addition, VFA-LDH and NH4HCO3 promoted increased soil fertility, including organic matter content, cation exchange capacity, and N and P contents. Overall, the developed technique exhibits great potential as an anaerobic fermentation liquid treatment and nutrient acquisition method.