Two Scottish scientists have perfected a method for making things out of vegetables. They are currently producing fishing rods made out of carrots, but hope to add rutabagas, turnips and parsnips to their melange. They say their technology will someday be used to create snowboards, engineering components and even battleships - replacing petroleum-based plastics.
Of course, the idea has been around for a long time. For example, in the dedication to the 1980 edition of Ringworld Engineers, Larry Niven wrote, "The Machine People would be able to use the vegetable sludge for other purposes, up to and including a plastics industry."
Some counter that we should not be using food to make plastics. This argument carries some weight in the ethanol debate (huge government subsidies leading to farmers switching to corn for ethanol production). I'd like to hear more on this argument vis-a-vis plastics made out of root vegetables. Fertilizer is a petroleum-based commodity (or so I hear). But perhaps legumes grown for the plastic industry could be grown in pure manure since we don't have to worry about them being safe to eat.