A flare stack that preferably comprises a burner assembly, an exhaust stack, an housing, and a fuel line. The burner assembly burns a fuel to generate thermal energy and combustion byproducts. The exhaust stack is cooperatively associated with the burner assembly to direct the thermal energy and combustion byproducts away from the burner assembly. The housing at least partially defines a fluid-receiving chamber in thermal communication with the exhaust stack. The fluid-receiving chamber has a heat-transfer fluid disposed therein. The fuel line is in fluid communication with the burner assembly to deliver fuel to the burner assembly. At least a portion of the fuel line is in thermal communication with at least one of the exhaust stack, housing, or heat-transfer fluid to permit fuel in the fuel line to absorb thermal energy before reaching the burner assembly. In one embodiment, the burner assembly includes a pressure-variable burner to increase the rate of fuel consumption of the burner in relation to the pressure in the fuel line. In the preferred embodiment, the housing has an inlet and an outlet formed therethrough in fluid communication with the fluid-receiving chamber. The inlet permits heat-transfer fluid to flow into the fluid-receiving chamber to absorb thermal energy from the exhaust stack, and the outlet permits heat-transfer fluid to flow out of the fluid-receiving chamber.