A cryogenic stream is pumped by a cryopump and then vaporized in a vaporizer to produce the pressurized vapor stream. The cryopump is driven by a transmission that is in turn driven by a hydraulic fluid. The hydraulic fluid flows within a hydraulic fluid circuit having first and second hydraulic fluid flow paths. The first of the flow paths is used to drive the hydraulic transmission. The second of the flow paths is dedicated to raising heat. Hydraulic fluid is circulated within the flow path by hydraulic fluid pumps and the amount of heat generated is controlled by adjustable back pressure valves. The adjustable back pressure valves in both fluid flow paths can be adjusted to control the degree to which heat is added to the vaporizer and therefore the pressurized vapor stream. The hydraulic fluid pumps can be driven by diesel engines. Heat may also be recovered from the diesel engines and gear oil used in pumps and the cryopump to also help vaporize the pressurized liquid stream. The aforesaid system of first and second pumps driven by an engine and first and second flow paths can be replicated to allow for expansion of pumping capacity.