Industries where gasification plays a large role in production processes can be ideal for CO2 capture and sequestration. The first steps to “Capture” are the separation and subsequent compression of CO2. Highly compressed CO2 is necessary if the goal is to store the CO2 in deep geological porous strata at its supercritical phase (the leading method of “Sequestration”). The porous strata levels are much deeper than most underground aquifers for drinking water. At its supercritical phase, CO2 is at greater than 1050 psig pressure and greater than 88 deg F.1 At these critical conditions, CO2 is neither liquid or a gas. Substantially more CO2 can be stored in its critical state (below 2600 ft) than at the earth’s surface. Geological sequestration requires a suitable repository. “A specific set of characteristics are needed to make a setting appropriate to act as a storage complex. These characteristics are determined through a rigorous characterization process that includes assessing potential storage risks and meeting the regulations under the U.S. Environmental Protection Agency’s (EPA) permitting process that grants permission to inject CO2 for carbon storage purposes”.2 act as a storage complex. These characteristics are determined through a rigorous characterization process that includes assessing potential storage risks and meeting the regulations under the U.S. Environmental Protection Agency’s (EPA) permitting process that grants permission to inject CO2 for carbon storage purposes”.2
Fertilizer plants present a key opportunity for the CO2 capture and storage, both because of the significant contribution to global CO2 emissions4 as well as the nature of the chemical process employed. These plants have capitalized on the recent low cost of natural gas as the hydrogen source to produce ammonia. Using steam methane reforming, a fertilizer plant catalytically reacts methane with steam at high pressures to produce hydrogen, carbon monoxide (CO) and a proportionally lower amount of carbon dioxide (CO2). Further downstream in the process, this CO is shifted to CO2 using H2O (steam) to produce even more H2 (i.e. this step is known as the water-gas shift reaction). While some of the produced CO2 is combined with NH2 to make urea (CH4N2O), a significant amount of CO2 remains as byproduct. For every ton of ammonia produced, 2 tons of CO2 are released, even for highly efficient ammonia plants.5
Consequently, fertilizer plants are concentrating current environmental efforts towards capturing this CO2 or not producing it in the first place. Leading producers are pursuing both Blue and Green Ammonia projects. Blue Ammonia production involves the manufacture of ammonia through steam methane reforming (SMR), coupled with carbon capture and storage (CCS). The Blue Ammonia projects seek to separate, compress and sequester the CO2 product via pipeline to underground repositories. Green Ammonia plants or projects do not generate CO2. Instead, these plants manufacture NH3 from H2 derived by the electrolysis of H2O. Besides being used to make fertilizer, the NH3, in-itself, can be an alternative future fuel that meets “carbon zero” goals during its combustion.
As mentioned earlier, gasification processes are key potential CO2 sources for CCS. Gasification is a process that converts carbon-based fuels at high temperatures without combustion. It uses a controlled ratio of oxygen to carbon and/or steam to produce carbon monoxide, hydrogen, and CO2 (www.energy.gov).6 Of note, cleaner gasification processes such as the integrated gasification combined cycle (IGCC) technology used in power plants are well-suited for CO2 capture and sequestration. Additionally, new bio-mass gasification projects can be candidates for CCS. Biomass as fuel can produce the H2 needed for fertilizer production. The biomass can substitute for natural gas or other carbon-based fuel sources such as coal. Since the biomass is recycled “carbon”, it can deliver a partial net-zero carbon footprint during gasification while producing energy, fertilizer or other chemical products.
REFERENCES
1 NETL (NATIONAL ENERGY TECHNOLOGY LABORATORY), DOE.GOV, “Carbon Storage FAQs”, https://netl.doe.gov/carbon-management/carbon-storage/faqs/carbon-storage-faqs, (accessed 09/28/2022).
2 Ibid, https://netl.doe.gov/carbon-management/carbon-storage/faqs/carbon-storage-faqs.
3 Dismukes, D.E., Zeidouni, M. et al., “Integrated Carbon Capture and Storage in the Louisiana Chemical Corridor,” Department of Energy, 2019.
4 Menegat, S., Ledo, A., & Tirado, R., “Greenhouse gas emissions from global production and use of nitrogen synthetic fertilisers in agriculture.” Scientific Reports, 12, 14490 (2022).
https://doi.org/10.1038/s41598-022-18773-w.
5 LeCompte, Celeste, 4/25/2013, “Fertilizer Plants Spring Up to Take Advantage of U.S.’s Cheap Natural Gas,” Scientific American, https://www.scientificamerican.com/article/fertilizer-plants-grow-thanks-to-cheap-natural-gas/, (accessed 10/5/2022).
6 Office of Energy Efficiency & Renewable Energy, Energy.gov, “Hydrogen Production: Biomass Gasification”, https://www.energy.gov/eere/fuelcells/hydrogen-production-biomass-gasification, (accessed 9/28/2022).
7 Rissman, Jeffrey, 10/8/2021, “Decarbonizing Chemicals and Other Industries in Louisiana”,
For the Louisiana Climate Task Force., p. 9.
8 Ragsdale, Rose, 10/27/2021, “Team Captures CO2 With Liquid Gallium,” Metal Tech News, https://www.metaltechnews.com/story/2021/10/27/tech-metals/team-captures-co2-with-liquid-gallium/, (accessed 9/14/2022).
9 Saudi Green Initiative, 11/2021, “From Waste to Resource: Can Recycling CO2 Help Saudi Arabia Go Green?”, The Independent, https://www.independent.co.uk/climate-change/sgi/carbon-dioxide-recycling-co2-saudi-arabia-green-b2182818.html,
(accessed 9/22/2022).
Meet the Author
Magdiel Agosto received a PhD in Chemical Engineering from Purdue University. His academic research work focused on modeling and scaling up bio-separations. After Purdue, he went to work for Exxon Chemical Co. His work there was closely tied to research and development involving manufacturing support in petrochemicals (catalyst screening, designing/running pilot plants/ toll-processing, troubleshooting units). He also co-authored several patents while at Exxon. He now continues his career with engineering service companies, where he conducts process design engineering for various refinery and petrochemical clients. Some of his projects include heat exchanger design/sizing, plant process simulation, tower and equipment revamps at all stages. Projects range from front-end to detailed engineering phases.