Production of shale oil yields a significant quantity of by-product gas that can have considerable value. The by-product, oil shale retort gas (OSRG), constitutes about 1/4 of the energy input of the shale that is processed in a Galoter-based retort. The desirability of producing separate products from OSRG is confirmed. Even one single component - propylene - has a potential market value of up to US$250 million per year if produced on the scale that Eesti Energia (EE) is proposing to develop its oil shale project in Utah, USA. Used in its aggregate state as a simple fuel in a power plant, the same amount of OSRG has only about 5% of that value.