A method of producing a hydrocarbon fuel from a soapstock includes supplying a pyrolysis reactor that includes a microwave absorbent bed susceptible to microwave irradiation, applying microwave energy to the pyrolysis reactor, wherein the microwave absorbent bed converts the microwave energy to thermal energy, supplying the soapstock to the microwave absorbent bed, and condensing a vapor generated by pyrolysis of the soapstock sufficient to collect the hydrocarbon fuel.