A processing apparatus to melt animal fat, in which an animal raw fat material is transported by a pump, through a microwave chamber and heated, the processing apparatus includes at least one solid-state radio frequency source that is configured to generate microwave energy, one or more sensors, and a control system. The at least one solid-state radio frequency source is configured to generate and transmit the microwave energy to the animal raw fat material, the one or more sensors are configured to measure the microwave energy that is reflected from the animal raw fat material, and the control system is configured to compare the transmitted microwave energy to the reflected microwave energy and then, based on the comparison, the control system is configured to adjust any additional microwave energy that is transmitted by the at least one solid-state radio frequency source to the animal raw fat material.