Life cycle energy use and greenhouse gas emissions of ammonia production from renewable resources and industrial by-products

Conventionally, ammonia is produced from natural gas via steam methane reforming (SMR), water-gas shift reaction, and the Haber-Bosch process. The process uses fossil natural gas, which leads to 2.6 metric tons of life cycle greenhouse gas (GHG) emissions per metric ton of ammonia produced. With amm...

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Bibliographic Details
Published in:	Green chemistry : an international journal and green chemistry resource : GC 2020-08, Vol.22 (17), p.5751-5761
Main Authors:	Liu, Xinyu, Elgowainy, Amgad, Wang, Michael
Format:	Article
Language:	eng
Subjects:	Ammonia By products Byproducts Carbon dioxide Distillation Electrolysis Emissions Energy consumption Energy resources Energy sources Fossils Green chemistry Greenhouse effect Greenhouse gases Haber Bosch process Life cycle analysis Life cycles Low temperature Natural gas Reforming Renewable energy Renewable resources Shift reaction Steam Sustainable yield
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Summary:	Conventionally, ammonia is produced from natural gas via steam methane reforming (SMR), water-gas shift reaction, and the Haber-Bosch process. The process uses fossil natural gas, which leads to 2.6 metric tons of life cycle greenhouse gas (GHG) emissions per metric ton of ammonia produced. With ammonia being the second most produced chemical in the world, its production accounts for approximately 2% of worldwide fossil energy use and generates over 420 million tons of CO 2 annually. To reduce its carbon intensity, ammonia synthesis relying on renewable energy or utilizing by-products from industrial processes is of interest. We conduct a life cycle analysis of conventional and alternative ammonia production pathways by tracking energy use and emissions in all conversion stages, from the primary material and energy resources to the ammonia plant gates. Of all the alternative pathways, obtaining N 2 from cryogenic distillation and H 2 from low-temperature electrolysis using renewable electricity has the lowest cradle-to-plant-gate GHG emissions, representing a 91% decrease from the conventional SMR pathway. Ammonia from renewables and industrial by-products has lower lifecycle fossil-energy use and greenhouse gases emissions than ammonia from natural gas.
ISSN:	1463-9262 1463-9270