A system comprising: a waste heat recovery heat exchanger (1, 2, 3, 4, 5, 6, 7) configured to heat a heating fluid stream by exchange with a heat source in a crude oil associated gas processing plant; and an Organic Rankine cycle energy conversion system (650, 651) including: an energy conversion heat exchanger configured to heat a first portion of a working fluid by exchange with the heated heating fluid stream, the working fluid comprising iso-butane, a cooling subsystem including one or more cooling elements each configured to cool one or more of a process stream from the crude oil associated gas processing plant and a cooling water stream for ambient air cooling by exchange with a second portion of the working fluid, an ejector configured to receive the second portion of the working fluid from the cooling subsystem and a third portion of the working fluid, the third portion of the working fluid being a portion of the heated first portion of the working fluid, a turbine and generator, wherein the turbine and generator are configured to generate power by expansion of a fourth portion of the working fluid, the fourth portion being a portion of the heated first portion of the working fluid, and a cooling element configured to cool a stream of working fluid including an output stream of working fluid from the ejector and the expanded fourth portion of the working fluid from the turbine and generator. a waste heat recovery heat exchanger (1, 2, 3, 4, 5, 6, 7) configured to heat a heating fluid stream by exchange with a heat source in a crude oil associated gas processing plant; and an Organic Rankine cycle energy conversion system (650, 651) including: an energy conversion heat exchanger configured to heat a first portion of a working fluid by exchange with the heated heating fluid stream, the working fluid comprising iso-butane, a cooling subsystem including one or more cooling elements each configured to cool one or more of a process stream from the crude oil associated gas processing plant and a cooling water stream for ambient air cooling by exchange with a second portion of the working fluid, an ejector configured to receive the second portion of the working fluid from the cooling subsystem and a third portion of the working fluid, the third portion of the working fluid being a portion of the heated first portion of the working fluid, a turbine and generator, wherein the turbine and generator are configured to generate power by expansion of a fourth portion of the working fluid, the fourth portion being a portion of the heated first portion of the working fluid, and a cooling element configured to cool a stream of working fluid including an output stream of working fluid from the ejector and the expanded fourth portion of the working fluid from the turbine and generator. an energy conversion heat exchanger configured to heat a first portion of a working fluid by exchange with the heated heating fluid stream, the working fluid comprising iso-butane, a cooling subsystem including one or more cooling elements each configured to cool one or more of a process stream from the crude oil associated gas processing plant and a cooling water stream for ambient air cooling by exchange with a second portion of the working fluid, an ejector configured to receive the second portion of the working fluid from the cooling subsystem and a third portion of the working fluid, the third portion of the working fluid being a portion of the heated first portion of the working fluid, a turbine and generator, wherein the turbine and generator are configured to generate power by expansion of a fourth portion of the working fluid, the fourth portion being a portion of the heated first portion of the working fluid, and a cooling element configured to cool a stream of working fluid including an output stream of working fluid from the ejector and the expanded fourth portion of the working fluid from the turbine and generator.