The conversion of liquefied natural gas (LNG) to pipeline-quality gas requires large quantities of low-grade thermal energy that may be available from industrial waste streams, steam power plants, or ocean water at the point of discharging LNG from the tanker. Alternatively, heat may be provided by the) combustion of LNG or another fuel. In either case, the large temperature differences between these heat sources and the temperature of the LNG can be Used to operate an engine that will offset or eliminate the pumping or fuel costs incurred.