This chapter aims to evaluate energy flows in the life cycle of biogas utilization (i.e., production of thermal energy, cogeneration, traffic, and production of hydrogen), starting from feedstock and anaerobic digestion, up to the digestate as fertilizer for agricultural production. The analysis is based on the out-turn of a biogas plant on the dairy farm Mirotin Vrbas, Republic of Serbia. Life Cycle Energy Assessment (LCEA), presented in this chapter, has demonstrated that three scenarios – biogas for heat production, biogas in cogeneration, and biomethane in transportation have positive energy balances, which indicate that in terms of replacement of fossil fuel consumption, these energy systems are promising alternatives. In the fourth scenario, where biogas is used for hydrogen production, the energy balance is negative, therefore socio-economical factors should be considered for overall consideration to ensure sustainability.