An experimental study on bio-oil production from co-pyrolysis with potato skin and high-density polyethylene (HDPE)

In order to investigate the synergistic effect of high dense polyethylene (HDPE) addition to potato skin (pS) during co-pyrolysis, pure HDPE was pyrolysed as a model compound for determination of the optimum process conditions. Thermal decomposition of pure HDPE was performed at constant heating rate of 5 °C min− 1 under various pyrolysis temperatures (400, 420, 450, 470, 500 and 550 °C) and sweeping gas flow rates (100, 200, 400 and 800 cm3 min− 1). The maximum bio-oil yield was 56% at 500 °C under sweeping flow rate of 400 cm3 min− 1. Then, co-pyrolysis of pure HDPE-pS and waste HDPE-pS mixtures were pyrolysed with various proportions such as 1:0, 1:1, 1:2, 2:1 and 0:1. The yield of liquids produced during co-pyrolysis enhanced with increasing weight ratio of HDPE in mixtures. Obtained bio-oils were analyzed in detail with various spectroscopic and chromatographic methods. Co-pyrolysis oil had higher carbon and hydrogen contents, lower oxygen contents with higher heating value than those of pyrolysis. It was concluded that addition of HDPE improved the liquid yields in terms of both quality and quantity.

► Co-pyrolysis of potato skin with pure and waste HDPE is investigated to optimize the experimental conditions for bio-oil production.
► When pS/HDPE ratio is increased to 1:2, the yield of bio-oil is increased to 50.88 %.
► The addition of HDPE to the mixture seemed to have increased the liquid production and decreased the gas formation.
► In the co-pyrolysis of HDPE and biomass, oxygen content in the oils were significantly reduced which can be attributed to influence of the HDPE.
► High amounts of 2-alkenes, 1-alkenes and alkadienes are obtained in the co-pyrolysis liquids fractions.