Biochemical methane potential and solid state anaerobic digestion of Korean food wastes

Abstract

In order to develop an anaerobic digestion process for Korean food wastes containing 15–30% total solids (TS) the biochemical methane potentials (BMP) of their components and mixture (mixed food waste, MFW) were measured. The methane yields of cooked meat, cellulose (as control), boiled rice, fresh cabbage and MFW were 482, 356, 294, 277 and 472 ml CH 4/gVS added and anaerobic biodegradabilities based on the stoichiometric methane yield were 0.82, 0.92, 0.72, 0.73 and 0.86, respectively. In a one-phase methane reactor system, VFAs were accumulated so excessively as to inhibit subsequent methane fermentation. Hence, the MFW with 20% TS was digested in solid-bed, two-phase systems of 1 l and 8 l methane reactors. In the 8 l methane reactor system, also, the effect of effluent recirculation to the solid-bed was studied. No nutrients, buffer or seed inoculum were added in the 5 l solid-bed. In all cases, 87–90% of TS in the solid-bed was reduced and approximately 90% of the initial bed volatile solid was converted to biogas. The treatment periods for the complete digestion of waste depended mostly upon the performances of the methane fermenter, especially on hydraulic retention time (HRT) and loading rates. The methane yield was around 405–415 ml/gVS reduced during entire periods. This value is about 86–88% of the BMP test data (the ultimate methane yield) with the same sample.