Anaerobic digestion (AD) is widely used to recover energy (in the form of methane) and nutrients (in the form of biofertilizer) from organic wastes, and adding conductive materials has been reported to be an effective way to enhance AD efficiency. However, the process performance and environmental sustainability of adding conductive materials into AD under different temperature conditions have not been addressed. In this study, four different groups of lab-scale reactors were operated under both mesophilic and thermophilic conditions and with/without activated carbon (AC) addition. Based on the lab-scale results, a pilot-scale reactor was used to highlight the effectiveness of activated carbon addition, and the derived data was used for a life cycle assessment (LCA) study. The results showed the enhancement of methane production by adding AC, particularly under thermophilic conditions. At the organic loading rate of 4.7 g VS/L/d, the average methane yield of the thermophilic AD reactors with AC was 550 mL CH4/g VS, which was significantly higher than that of the control reactors (i.e. 220 mL CH4/g VS). Adding AC into AD reactors accelerated the shift of dominant methanogenic pathways from aceticlastic methanogenesis to hydrogenotrophic methanogenesis by enriching Methanoculleus (84% of total archaea). The LCA results highlighted the environmental benefits of using activated carbon to enhance AD of food waste at both midpoint and endpoint levels based on ReCiPe2016 methodology.