Liquid and gas products from lead acid battery derived plastics via pyrolysis: a techno-economic assessment to maximize the value

Lead acid batteries (LAB) are efficient, safe and low cost. Their market was valued at 37.5 billion $ in Europe alone in 2020. The main application in the automotive sector is starting, lighting and ignition (75%). Polymeric materials account for 22-30% of the whole end-of-life battery and hold great value. The aims of this work are 1) to gather experimental data and assess liquid and gas production for LAB-derived plastics pyrolysis with different operating conditions in a laboratory-scale rector, 2) to perform a techno- economic evaluation of the pyrolysis of this feedstock and to determine the economic sustainability of the scale- up of the considered process, 3) to compare the investigated processes and products and define the most advantageous configuration. LAB-derived plastics have been pyrolyzed in a mechanically fluidized reactor (MFR) at 550-650°C. During each experiment, 300 grams of feedstock have been continuously processed to gather experimental data on yields and products quality. The economic assessment is based on two scenarios: selling oil and gas, or gas only. The plant is scaled up to be able to treat the annual amount of plastic of 3,000 tons. Moreover, a top-down analysis is performed to define the minimum plant size required for the process to be industrially realized. The scale-up scenarios consider the economic parameters and the influence of different energy sources. Liquid production is maximized at 550°C with a yield of 45%, the gas is the second major product composed mainly of methane (18%) and hydrogen (11%). Increasing the temperature to 650°C spikes the gas yield to 45% of which 39% is hydrogen. Moreover, no liquids are formed at this temperature. Conversion efficiencies of this level and the absence of liquids under thermal pyrolysis conditions have not been reported before. Pyrolysis of LAB’s plastic for oil production is not economical in any scaled-up case. There is a substantial decrease of 14 M$ in the net present value (NPV) when switching from electricity to natural gas for both plant sizes 3 Kt year -1 and 10.5 Kt years -1. Nonetheless, the most favorable situation employing part of the methane produced in the gas as heating source has a negative NPV of 10 M$ after 20 years of operation. When considering gas production, the scale-up to 3 Kt year -1 is not profitable during the plant life when induction is the heating source: net present value of -8 M$. Switching the heating source to natural gas allows for an even closure (0 M$) at 20 years, this is a great improvement, but it is not sufficiently appealing to industrial partners. Recirculation of the methane produced into the system achieves energetic self-sustainability. This scale-up scenario presents a payback period (PBP) of 16.5 years and an NPV at the end of life of 1 M$. Successful industrial plants have payback periods of 3-5 years; in this work, a PBP of 4 years is achievable by increasing the size of the plant to 10,500 tons per year and by using the methane produced as heating source. In this scenario, a net present value of 41.1 M$ is reached after 20 years and an internal rate of return (IRR) of 30%, which is very promising for investors. Oil production via pyrolysis of LABs derived plastics is not economical and industrial application is discouraged. Thermal pyrolysis at high temperatures is a promising technology for hydrogen production with methane energy recovery: it is energetically self-sustainable and economically advantageous