(390v) Boosting U.S. Ammonia Competitiveness Via Biogas Utilization: Modeling, Techno-Economic Analysis, and Geospatial Sensitivity Studies

Ammonia production is a major contributor to industrial energy use and greenhouse gas emissions, with a footprint of 41 GJ and 2.4 t CO₂eq per metric ton of NH_3. [1]. In this study, we evaluate the feasibility of using biogas derived from waste (i.e., landfills, wastewater treatment, and agricultural waste) as a low-carbon feedstock to decarbonize ammonia production in the United States (U.S.), leveraging process simulation, techno-economic analysis (TEA), and geospatial modeling.

We developed detailed steady-state Aspen Plus models for five ammonia production pathways from biogas: steam methane reforming (SMR), autothermal reforming, catalytic partial oxidation, methane pyrolysis (MP), and chemical looping reforming. Each route integrates a biogas upgrading unit, carbon capture, and ammonia synthesis via the Haber-Bosch process. Key performance indicators include fuel usage, energy efficiency, global warming potential (GWP), minimum ammonia selling price (MASP), and cost of CO₂ avoided (CCA). A design basis of 62.5 metric tons of NH₃ per hour was used, the average plant size of commercial NH₃ plants in North America [2].

On a methane basis, biogas-fed SMR with carbon capture achieves 34 GJ t-NH₃^-1 and 54.6% efficiency—comparable to natural gas-fed SMR with carbon capture (32.5 t-NH₃^-1, 55%). The biogas-fed NH₃ process enables the capture of 1.75 t-CO₂ t-NH₃^-1 of biogenic carbon, contributing to net carbon removal. However, its MASP ($552 t-NH₃^-1) is approximately twice that for conventional NH₃ ($229 t-NH₃^-1), resulting in a CCA of $194 t-CO₂eq^-1. Among the alternative technologies evaluated, MP outperforms other designs considered, offering the lowest MASP ($445 t-NH₃^-1) and CCA ($90.6 t-CO₂eq^-1), aided by carbon black valorization.

A cost structure analysis reveals that electricity, feedstock, and capital expenditures are the primary drivers of MASP, with significant variations across technologies. We extend the analysis using U.S. state-level data on biogas availability, electricity price [3], and grid carbon intensity [4]. These disparities result in substantial variation in MASP across the U.S., ranging from $500 to over $850 per ton of NH₃, depending on the location, with Texas and parts of the Northeast offering optimal conditions. CCA also varies widely across the country.

This work provides a comprehensive evaluation of biogas as a renewable feedstock for ammonia production. It demonstrates that biogas-based SMR and MP offer viable, low-carbon alternatives with performance competitive to that of conventional processes. The modeling framework supports technology selection, site optimization, and investment decisions and can be extended to other biogenic process pathways. Ultimately, biogas-to-ammonia pathways present a compelling opportunity for circular, low-emission chemical manufacturing in the U.S. and beyond.

References

1. IEA, Ammonia Technology Roadmap. 2021, International Energy Agency.
2. Nutrien, 2023 fact book. 2023.
3. Electric Power Monthly - U.S. Energy Information Administration (EIA).
4. Emissions & Generation Resource Integrated Database (eGRID) | U.S. EPA.