An integrated environmental control system for an aircraft compartment and aircraft power system comprises first and second air compressors, an auxiliary power unit, and first and second environmental control systems. The first and second compressors receive and compress airflow from the aircraft exterior. The auxiliary power unit comprises a first shaft rotatably mounting a power turbine, a third air compressor to compress airflow from the aircraft exterior, and a first cooling turbine to cool the airflow. Each environmental control system comprises a first heat exchanger, a recycling heat exchanger, and a second shaft rotatably mounting a fourth compressor and a second cooling turbine for compressing and cooling the airflow. The first heat exchanger receives airflow from the first, second, and third air compressors and forwards airflow to the aircraft compartment. The recycling heat exchanger receives airflow from the aircraft compartment and recirculates airflow back to the aircraft compartment.