Biogas upgrading for removing CO

2

and other trace components from raw biogas is a necessary step before the biogas to be used as a vehicle fuel or supplied to the natural gas grid. In this work

three technologies for biogas upgrading

i.e.

pressuredwater scrubbing (PWS)

monoethanolamine aqueous scrubbing (MAS) and ionic liquid scrubbing (ILS)

are studied and assessed in terms of their energy consumption and environmental impactswith the process simulation and green degree method. A non-random-two-liquid and Henry's law property method for a CO

2

separation system with ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim

]

[Tf

2

N

]

) is established and verified with experimental data. The assessment results indicate that the specific energy consumption of ILS and PWS is almost the same and much less than that of MAS. High purity CO

2

product can be obtained by MAS and ILS methods

whereas no pure CO

2

is recovered with the PWS. For the environmental aspect

ILS has the highest green degree production value

while MAS and PWS produce serious environmental impacts.