Acid gas absorbent in biogas and biogas purification system using the same

An absorbent for absorption of an acid gas in a biogas, comprising:

• a tertiary amine represented by the following chemical formula 1;
• a primary or secondary amine;
• and
• a solvent,
• wherein R1 is linear or branched C1-C5 alkyl or linear or branched C2-C5 alkenyl;
• and
• R2 and R3 are independently linear or branched C1-C10 alkyl having a terminal thereof unsubstituted or substituted with a hydroxyl group, or linear or branched C2-C10 alkenyl having a terminal thereof unsubstituted or substituted with a hydroxyl group,
• wherein at least either one of the R2 and R3 is linear or branched C1-C10 alkyl having a terminal thereof substituted with a hydroxyl group, or linear or branched C2-C10 alkenyl having a terminal thereof substituted with a hydroxyl group.