**6.2 Biological technologies**

The biological biogas upgrading technologies are classified into chemoautotrophic and photosynthetic. Most of these configurations have been practically proven and are at an initial step of pilot or full scale application. The main benefit of such techniques is associated to the fact that the CO2 is transformed into other energy containing or valuable added products at mild operational conditions (i.e., moderate temperature levels, atmospheric pressure) contributing extremely to a circular economy and sustainable bio-based.
