Co-Pyrolysis of Potato Peels and Polystyrene : A Novel Technique to Recover the Upgraded and Valuable Bio Oil

The whole world is searching for novel and sustainable techniques for production of renewable fuels and valuable chemicals via a route which is clean, economical, energy saving and fast process. In this context, mixture of potato peels and polystyrene in different weight ratio were taken as feed for production of bio oil through co-pyrolysis. The product bio oil could be reformed to produce a renewable and clean source of energy from waste biomass and plastics. This novel technique undoubtedly will reduce the threat to depletion of fossil fuels. The potato peel was selected due to its high hydrocarbon contents and abundance in nature while the latter (polystyrene) has high hydrogen content, thus would add value to the oil through synergistic effects. Also, its consumption to produce a fuel, would minimize the environmental menace created by plastics.

TG-DTA analyses were carried out on raw materials to investigate their thermal degradation properties and other tests like proximate and elemental analyses were done to characterize it. The pyrolysis of pure potato peels was carried out initially at different temperatures and the optimum temperature was found to be 500^oC to achieve highest liquid yield. Then co-pyrolysis of processed potato peels and polystyrene was performed at this temperature in different weight ratios and the oil obtained with 1:3 weight ratio of potato peels and polystyrene showed the bio oil yield of 67.17 weight % which is quite higher than yield of pure potato peels (38.1 weight %). The GC-FID and FTIR spectrum results confirmed that the synergistic effects between biomass and polymer during co-pyrolysis resulted in reducing the oxygenated compounds in the oil, as evident by the rise in calorific value from 24.18 MJ/kg of bio oil obtained from pure potato peels (500^oC) to that of 33.42 MJ/kg through co-pyrolysis of potato peels to polystyrene (1:3) at 500^oC. Also, other properties and fuel tests were performed for characterizing liquid, like pH, density, flash & fire point, water content, ASTM distillation which proved that the bio oil produced via co-pyrolysis process has a potential to be used as fuel.

The solid product Char was also analyzed for its properties through proximate analysis, fixed carbon test, calorific value and FTIR to determine the possibility of developing the char into a solid fuel or its use as an activated carbon in extraction processes of heavy metals. It was concluded that the co-pyrolysis of potato peels and polystyrene evaluates as a promising technique for recovering upgraded bio oil and valuable char.