A combined diesel gas-turbine system for optimizing operation and combustion processes of a diesel engine includes a catalytic sub-system, a turbo-generator sub-system and a hybrid sub-system. The catalytic sub-system is in communication with an exhaust port of the diesel engine and is operative for combusting and reducing all pollutants from diesel exhaust. The catalytic sub-system is a three-way catalytic converter and a first catalytic converter in series with a second catalytic converter. The turbo-generator sub-system is operative for the reclamation of secondary energy from the catalytic sub-system and includes a turbine in communication with the second catalytic converter for receiving a source of cleaned exhaust gas to drive the turbine. The hybrid sub-system is operative for the management of energy within the system. The system may incorporate a waste heat recovery system and convert it to mechanical power. The system may include a steam generator for the recovery of waste heat from the post turbo-charger exhaust. The combined diesel gas-turbine system is capable of reducing all diesel engine pollutants to near-zero levels and increase thermal efficiency.