After solving the optimization model, we obtain the optimal pathways for plastics production with minimized production cost. Figure shows the optimal pathways in the base case scenario where no carbon pricing is implemented. The optimization model suggests that all the plastics should be manufactured from naphtha or natural gas in order to achieve a minimum production cost. This result is consistent with the current industrial practice, where more than 99% of plastics are made from fossil fuels, and implicitly indicate that biomass pathways are not cost-competitive. The model also indicated that the total production cost to meet all the plastic demands is $538.2 billion per year, and the total GHG emissions are 722.3 million tonnes CO 2 -equivalent (MtCO 2 eq) per year.