Food waste was characterized for its potential use as substrate for anaerobic co-digestion in a submerged
anaerobic membrane bioreactor pilot plant that treats urban wastewater (WW). 90% of the particles had
sizes under 0.5 mm after grinding the food waste in a commercial food waste disposer. COD, nitrogen and
phosphorus concentrations were 100, 2 and 20 times higher in food waste than their average concentrations
in WW, but the relative flow contribution of both streams made COD the only pollutant that
increased significantly when both substrates were mixed. As sulphate concentration in food waste was
in the same range as WW, co-digestion of both substrates would increase the COD/SO4-S ratio and favour
methanogenic activity in anaerobic treatments. The average methane potential of the food waste was
421 ± 15 mL CH4 g1 VS, achieving 73% anaerobic biodegradability. The anaerobic co-digestion of food
waste with WW is expected to increase methane production 2.9-fold. The settleable solids tests and
the particle size distribution analyses confirmed that both treatment lines of a conventional WWTP
(water and sludge lines) would be clearly impacted by the incorporation of food waste into its influent.
Anaerobic processes are therefore preferred over their aerobic counterparts due to their ability to valorise
the high COD content to produce biogas (a renewable energy) instead of increasing the energetic costs
associated with the aeration process for aerobic COD oxidation.