little more on adsorption:
Adsorbed Natural Gas (ANG) vs. LNG and CNG - scopeWe - a Virtual Engineer
"The amount of adsorbed and delivered natural gas strongly depends on the type of adsorbent solids used. There are two important numbers: 213 v/v is the maximum theoretical capacity of activated carbon, and 120 v/v that is the capacity of usual adsorbents. Reaching to the maximum theoretical capacity from the low normal capacity of adsorbents has been the activating energy to expand ANG industry. It is notable that 150 v/v is known to be economical capacity for industrial adsorbents. "