Assessing climate change impact of blue ammonia via carbon capture and utilization in life cycle modelling

Abstract

Ammonia production represents a fundamental aspect of the global chemical industry. It is a significant contributor to carbon dioxide (CO₂) emissions, and it is necessary that innovative methods be developed to reduce its climate impact. This study assesses the environmental impact of blue ammonia production incorporating carbon capture and utilization (CCU) through a novel Life Cycle Assessment (LCA) approach, based on the latest guidelines from the Together for Sustainability (TfS) initiative. This analysis is centred on three systems: grey ammonia (System A), blue ammonia with in-process carbon capture (System B), and blue ammonia utilizing system expansion via direct air capture (DAC) (System C). The results demonstrate that the production of grey ammonia in Germany generates 3.12 kgCO_2eq per kg of ammonia, predominantly due to emissions from steam methane reforming (SMR). The incorporation of in-process CO₂ capture in blue ammonia (System B) results in a climate impact of 1.79 kgCO_2eq for the functional unit of 1 kg ammonia plus 1.85 kg of succesfully captured CO₂. The implementation of system expansion via DAC (System C), as recommended by the TfS guidelines, results in a further reduction of ammonia emissions to 2.64 kgCO_2eq, in comparison to System A. This approach also yields a net negative impact of −0.85 kgCO_2eq for the captured CO₂ co-product, enabling the realization of the shared incentivization objective articulated in the suggested guideline. The regional scenarios convincingly demonstrate that the proposed approach achieves varying levels of success, often leading to more polarized incentivization. The future scenario will significantly enhance the benefits of CCU and the utilization of CO₂ as a co-product. However, this will be at the expense of incentivizing the production of blue ammonia. This work advances the methodologies for LCA of multi-functional CCU systems, demonstrating the potential for shared incentives in the transition to a new ammonia generation system as a prime example. Nonetheless, it also highlights limitations in regions where the energy source is dominated by fossil fuels or where the energy source is fully renewable. The current TfS framework methodology proposition is therefore a short-term solution to promote the sustainable production of blue ammonia with CCU applications.