Anaerobic codigestion with fruit and vegetable wastes: An opportunity to enhance the sustainability and circular economy of the WWTP digesters

Abstract A conventional wastewater treatment plant (WWTP) uses anaerobic digestion (AD) for the stabilization of sewage sludge (SS), regardless of the performance of the digester as biogas producer. Nevertheless, this performance can be improved if another residue is codigested together with SS. Therefore the operational conditions of the digester to achieve the stabilization should be maintained with the introduction of the complementary cosubstrates. Fruit and vegetable waste (FVW) is probably the best candidate for such codigestion. FVW can be introduced in the digester in a wide range of volumetric ratios without affecting the stability of the digester. Nevertheless, some risks should not be overlooked, regarding the possible acidification and failure of the digester. Some early warning parameters can be used to allow the operation of the digester preventing those risks. Therefore anaerobic codigestion of organic wastes is considered as a way to improve the sustainability and the circular municipal economy.