Production and utilization of renewable energy sources (e.g. biogas) are justified not only by energy-political, but by environmental aspects, too. It can be verified the necessity of the complex ecological aspects by biogas production experiments and its utilization tests in gas engines therefore we created a complex biogas production and utilization system, so that both the energy and the environmental goals can be achieved together. In the interest of an optimal solution it is necessary to analyze the two objective functions (the production and utilization functions) together, considering that the principle of the complex optimization focuses just on the environmental-friendly energy utilization. The centre of this system is the integrated waste-management. Its advantages are the local and global environmental results, energy production independent of external influences, as well as a near optimum solution ecologically.