Regional plastic waste recycling through pyrolysis – a techno-economic evaluation

Abstract

The aim of this thes is was to investigate the economic feasibility of plastic waste recycling by pyrolysis-based processes on a regional scale. The Gothenburg region was used as a reference regarding the volumes of plastic waste flows. The initial part of the project was a mapping of the regional and national waste flows to see how the amounts of different polymers compare to each other, establishing the possibility of treating certain flows separately. Parallel to this, a literature study was performed to investigate the current processes for treating plastic polymers using pyrolysis. Four different processes were modelled using the flow-sheeting software Aspen Plus inb oth regional and national scale; one process handling mixed plastics, one handling polyvinyl chloride (PVC) and two handling polystyrene (PS), the two latter being one simpler and one more complex, with different degrees of product separation. With the process layouts established, investment costs, revenues and running costs were calculated for both the regional and national scale plants. A cash flow analysis was conducted to assess the feasibility of regional plastic waste recycling by pyrolysis. The economic performance of regional scale plants was compared to the national scale plants. The results show that economies of scale have a large impact on profitability and with the current price setting, only the national scale mixed process handling 320 kt/yr shows any potential to raise interest from investors, with a pay-back period (PBP) of seven years. The simpler PS process and the more complex PS process have a PBP of 15 and 17.5 years respectively, the difference mainly arising from the substantially higher investment cost for the more complex process which is not compensated by the extra revenue. The PVC process is nowhere near profitable in any of the cases, mainly due to the complexity of the process and the low value of the products. Even though the national scale mixed process is promising, one drawback is that it does not treat wastes containing PVC, hence leaving the waste management problem with PVC unresolved.