Biomass-derived ammonia production via chemical looping: process modeling, experimental validation, and techno-economic evaluation

Ammonia is a critical chemical with widespread applications, serving both as a key commodity chemical in the fertilizer industry and as a promising hydrogen carrier for energy storage and transport. Given its central role in industrial and energy systems, it is imperative to develop sustainable pathways for ammonia production that minimize carbon emissions and dependence on fossil resources. The objective of this research is to develop a sustainable method for producing a hydrogen‑nitrogen (H₂/N₂) mixture with a molar ratio of 3:1, which is the stoichiometric feed for ammonia synthesis. Conventional approaches, such as steam methane reforming (SMR) coupled with autothermal reforming, are both energy-intensive and carbon-emitting. In contrast, the proposed process utilizes biomass-based chemical looping technology to directly generate the H₂/N₂ mixture in the desired 3:1 ratio, offering a low-carbon alternative to conventional methods. The proposed process is first modelled using Aspen Plus and subsequently validated through experiments conducted on a 2.5 kWth bench-scale reactor. Experimental results demonstrate the generation of a H₂/N₂ gas mixture in the desired 3:1 ratio and sequestration-ready CO₂, aligning with the goals of carbon-neutral ammonia production. The system achieves steam conversions close to thermodynamic limits, indicating high process efficiency. A comparative techno-economic analysis is conducted between the chemical looping-based process and conventional steam methane reforming. The findings reveal that the chemical looping process reduces the minimum selling price of ammonia by approximately 56.3 %, highlighting its potential as a cost-effective and sustainable alternative.