Modelling assessment of resource competition for renewable basic chemicals and the effect of recycling

Abstract

This work assesses pathways towards a net-zero greenhouse gas (GHG) emissions chemical industry sector in Germany until 2050, focusing on the ammonia, methanol, ethylene and adipic acid subsectors and the effect of the recycling of C embedded in chemical end products on the GHG abatement cost and primary resource demand. This was done using a bottom-up mathematical optimization model, including the energy sectors and the chemicals sector, with electricity and biobased options considered. Results show that net-zero GHG emissions for the considered chemicals in 2050 are attainable at a marginal cost of 640–900 €/tCO₂-eq, even with 26%–36% of demand being satisfied by fossil production routes. This is possible because renewable organic chemicals can act as carbon sinks if, at their end of life, C is permanently stored via landfilling or passed on to the next value chain via recycling. Nonetheless, considering the cost implications, the practical deployment of renewable chemicals is a challenge. The considered renewable chemicals cost 1.3–8 times more than their fossil counterparts, resulting in a marginal CO₂ price of 480 €/tCO₂-eq when all primary resources (energy crops, forest residues and renewable electricity) are considered, or 810 €/tCO₂-eq when the availability of arable land is restricted. In the transition to net-zero emissions for the chemicals under study, a circular economy is important not only for reducing demand for primary resources as is typically the case but also reduces GHG abatement costs by 13%–24% through carbon capture and utilization effects.