Stabilization of anaerobic co-digestion of biowaste using activated carbon of coffee ground biomass

[Display omitted] •Coffee ground biomass-derived hydrochar (CB-HTC) could improve stability of AcoD.•Surface morphology of CB-HTC was increased via KOH-activation to produce ACB-HTC.•CB-HTC and ACB-HTC improved biogas yield by ~5% relative to control digester.•ACB-HTC was most effective in improving stability of AD due to improved DIET.•High quality digestate suitable as organic fertilizer was obtained with ACB-HTC. Process instability commonly encountered in anaerobic co-digestion (AcoD) of organic fractions of municipal solid wastes (OFMSWs) is addressed by utilizing hydrochar (CB-HTC) and activated hydrochar (ACB-HTC) derived from coffee ground biomass. Addition of CB-HTC or ACB-HTC shortened the lag phase resulting in high biogas yield of 68.57 Nl/kg oTS or 102.86 Nl/kg oTS, respectively within the first week. Improvement in biogas yield (~5% higher than the control) was due to unique properties which prevented washout of consortia of bacteria useful for AcoD and subsequently led to a more stable process. An increase in either OLR [1.0 kg oTS/(m3*d) to 1.5 kg oTS/(m3*d)] or temperature (36.5 °C to 42.5 °C) did not lead to increase in ammonium-nitrogen or TKN in reactors amended with hydrochars. Likewise, ratio of VFA/TA was within 0.2–0.3 after the fourth week in ACB-HTC treated reactor. Addition of ACB-HTC greatly improved nutrient retention in the digestate.