Pyrolysis of High-Density Polyethylene Waste Plastic to Liquid Fuels—Modelling and Economic Analysis

Abstract

Recycling of waste plastics has become vital due to the threat to the environment the huge piles of those wastes represent, with research revealing High-Density Polyethylene (HDPEs) as the most dominant waste plastics. Because of their dominance and significant environmental impact, this paper reports the economic potential of recycling HDPE waste plastic into liquid fuels via pyrolysis. A risk and benefit assessment are presented to highlight whether the process has reasonable potential prior to the analysis of its corresponding finances. Aspen HYSYS simulation models were used as the basis for the analysis. From this, preliminary cost estimations for the net present value (NPV) of the process, its economic viability, were determined. It is shown that 100 kg/h of waste is not financially sustainable. Retailing the fuel product at a competitive price of £60/barrel would ultimately bankrupt the business. This is a consequence of the extremely high production cost of £198.40/barrel inducing the complete absence of profitability. Furthermore, the operating expenditure is found to be the root cause of the consequential financial decline, totalling £1.46 million per annum. The two most detrimental expenditures for the production cost of the pyrolysis oils were the wages of the skilled operating labour and higher utility fees incurred by the extreme temperature conditions. In addition, an unrealistically optimistic sale price of £300/barrel was also applied to ascertain a positive economic incentive. Even with the increased retail price, the process’ profits are negligible and further highlight the detrimental effect of the undesirably high operational expenditures, once more signifying that the process should not commence in its current state. However, executing such a project in developing countries such as Sierra Leone, Senegal, or Kenya where utilities and manpower, among other operational components, are cheaper, is believed to complement the immense opportunity underlying pyrolysis oil production regarding production quantity and quality.