The study found that by dissolving polystyrene packing peanuts in biodiesel, scientists can actually increase the power output of the fuel, while finding a solution to disposing of the material at the same time. The polystyrene, a polymer used to make disposable styrofoam, can be dissolved into biodiesel at a concentration of 2 to 20 percent, though power output tends to decrease as polystyrene concentration increases. Although plastic doesn’t break down easily in petroleum-based diesel, it breaks down almost instantly in biodiesel.
Iowa State University researchers Najeeb Kuzhiyil and Song-Charng Kong tested the polystyrene-biodiesel blend in a tractor engine. They found that power output increased as polystyrene concentrations increased to 5 percent. After 5 percent, however, power output tended to drop off as the polymer increased the biodiesel’s viscosity.
When the fluid gets too viscous, it doesn’t completely combust in the engine, leading to a power output decrease and potential for overheating of the fuel injection pump.
Though it is usually more energy efficient to recycle trash rather than convert it to fuel, polystyrene may be an exception as it’s not as easily recycled, economically speaking, in the industry. This makes the material a likely candidate for fuel conversion.
While the biodiesel mix has both environmental and economic advantages, it is not free of problems. As the concentration of polystyrene in the mix increases, so do the emissions of carbon monoxide, soot and nitrous oxides, which don’t completely burn off in the engine. The study co-authors hope to refine the engine’s fuel injection system to yield a more complete burn and fewer emissions.