Assessment of accidental refinery wastewater discharge: a case study

Carbon dioxide (CO₂), one of the green house gases (GHGs) is well known for more than a century. Its emission from the combustion of fossil fuels in addition to other industrial sources is adversely affecting the climate on earth. Climate change is emerging as a risk all over the world that has generated public concern. Estimates have indicated that power production contributes to the tune of 70% of the total CO₂ released into the atmosphere from fossil fuel combustion worldwide. Capturing and securely storing CO₂ from the global combustion systems thus constitutes an important and achievable target. A legion of researchers have thus far developed absorbents to remove CO₂ from combustion facilities that are currently recognized globally as most effective. The cost of capturing CO₂ can be reduced by finding a low-cost solvent that can minimize energy requirements, equipment size, and corrosion. Monoethanolamine is being used for removing CO₂ from the exhaust streams and is a subject inculcated over a period of about last 80 odd years. Host of such other amines are being investigated and put into practice. However, commercializations of such operating plants for capturing CO₂ from power plants in the world are few and far between. On the other hand, aqueous ammonia is the other chemical solvent for capturing CO₂ that has proven experimentally to be more effective than amine-based processes. This communication aims at critically elucidating relative merits and demerits of ammonia and amine-based CO₂ capture options from the exhausts of coal fired thermal power plants (TPPs). It includes the life cycle CO₂ emissions for both the processes. Finally, it is estimated that a total emission of about 152 Mt CO₂-equivalent could occur after use of 100 Mt ammonium bicarbonate (NH₄HCO₃) as synthetic N-fertilizer that is about 50% of the total CO₂ captured (315 Mt) for producing the fertilizer, NH₄HCO₃. Clearly, this estimate demonstrates that the synthetic N-fertilizer, NH₄HCO₃, produced by NH₃ scrubbing of CO₂ from fossil fuel (e.g., coal) fired TPP could have a significant beneficial environmental impact so far as GHG emission is concerned.