EU Research Project looks at feeding biogas into the main natural gas grid April 8, 2007 "A key technology for injection of biogas into the natural gas grid is upgrading of the biogas to natural gas quality after which it can be compressed to transport grid pressure. Biogas consists of around 50 to 65% of methane, small fractions of other compounds and 50 to 35% of carbon dioxide, which has to be removed before injection." Some of the current technologies discussed in this article include membrane separation technology, pressure swing adsorption, and cryogenic separation. http://biopact.com/2007/04/eu-research-project-looks-at-feeding.html -- LEVY,CHERONA L