As a result of the depletion of our supplies of oil and gas, which were created by the process of photosynthesis, it is now necessary to develop renewable fuels for the future because of the environmental problems associated with the expanding development of coal and oil shale, particularly the carbon dioxide problem. The most immediate source of renewable fuels is annually growing green plants, some of which produce hydrocarbons directly. We can select new plant sources that have high potential for production of liquid fuels and chemicals. Suggestions are made for the modification of both the product character and the productivity of the plants. Ultimately a totally synthetic device will be developed for the conversion of solar quanta into useful chemical form, completely independent of the need for arable land.