The effects of microelements (zinc and copper) supplementation (provided as ZnSO₄ and ZnCl2 at 50, 70, and 100 mg/L Zn²⁺ and as CuSO₄ and CuCl₂ at 10, 30, and 50 mg/L Cu²⁺) on biogas (methane) production was evaluated while co-digesting a mixture of food waste(water) and domestic wastewater. Regardless of zinc and copper supplementations, it is clear both microelements had an increase in the cumulative methane yield when compared to the control (p<0.05) and suggests they provided the synthesis of enzymes required for both acetoclastic and hydrogenotrophic methane production. The supplementation of zinc and copper stimulated the conversion of organic matter to methane at concentrations 50-100 mg/L and 10 mg/L, respectively. It can be assumed the improvements on the cumulative methane yield obtained could be associated not only by the intermittent feed strategy but specially by the micronutrient supplementation. Microelements may improve the LCFAs removal by two different mechanisms, biological and precipitation. The role of each mechanism should be further studied but definitely both contributed to alleviate the toxic effects of LCFAs in a great extent and the UASB reactor operate under stable and steady condition during 260 days.