Activated carbon (AC) may improve methane production, but its performance can depend on substrate loading and incubation time. This study evaluated 60-day batch anaerobic digestion of food wastewater at 38 °C using substrate-to-inoculum (S/I) ratios of 0.5, 1.0 and 1.5 on a volatile-solids mass basis, three nominal AC particle sizes (4, 45 and 150 μm), and AC doses of 5 and 10 g/L. In the processed dataset, at S/I = 1.5 the highest day-5 methane yield was 49.9% above the control, whereas day-60 yields were lower than the corresponding controls in all AC treatments. Endpoint soluble Ni concentrations were lower in all AC treatments, and Co concentrations were generally lower. The metal pattern suggests a possible association between nutrient availability and final methane yield. The results highlight the need to assess early methane gains together with final yield and metal availability. AC plus trace-element supplementation should be evaluated in future studies before operational recommendations are made.