The biological catalysis is facilitated by an archaeal community of hydrogenotrophic methanogens, which occur naturally in the last step of traditional anaerobic digestion. These methanogens are classified as strictly anaerobic with no tolerance to oxygen . However, aside from oxygen, the microbial catalyst has a high tolerance against impurities, can regenerate through continuous microbial growth, and works at mild operation conditions at temperatures ranging from 35°C to 70°C and at pressures from 1 to 10 bar .