4E's (Energy, Exergy, Environment, and Economic) evaluation of biogas purification integrated with CHP using amine & ionic liquids

The use of 1-butyl-4-methylimidazolium acetate ([BmimAc]) combined with amine solvents—methyl diethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), and diisopropylamine (DIPA)—was investigated to produce high-purity biomethane (≥ 99 wt%) while maximizing process efficiency. Integrating biogas upgrading with combined heat and power (CHP) technology, the system met energy demands and generated sustainable electricity. The1-butyl-4-methylimidazolium acetate + 2-amino-2-methyl-1-propanol [BmimAc+AMP] system emerged as the best performer. While the [BmimAc+DIPA] system had lower energy consumption, it faced challenges such as ionic liquid loss. Exergy analysis revealed that the [BmimAc+AMP] system minimized energy waste by reducing exergy destruction, leading to a more efficient process with a low exergy destruction factor. Environmentally, this system also significantly reduced carbon emissions due to its higher efficiency. Economically, the [BmimAc+AMP] system was the most cost-effective, making it the most affordable option for biogas upgrading and CHP generation. While this approach showed great promise, challenges such as ionic liquid loss and scaling up for large-scale applications remain to be addressed.