Low quality, or "subquality" natural gas is that gas that has one or more impurities that prevent it from being put into a pipeline without going through a pretreatment process to remove the impurities. Subquality natural gas has been defined as having equal to or more than 2% carbon dioxide, 4% nitrogen, or 4 parts per million of hydrogen sulfide. Based on this criteria, approximately one third of U.S. reserves, or about 53 trillion cubic feet, in the lower 48 states are subquality. Source: Chemical Composition of Discovered and Undiscovered Natural Gas in the United States - 1993 Update. Gas Research Institute, Chicago, Illinois. (This organization is now known as the Gas Technical Institute. (www.gastechnology.org)
A substantial portion, perhaps 10%, of these low quality reserves are in small fields where conventional gas processing technology is uneconomic. This is where Gas Separation Technology's Carbo-X and Air-X processes, designed to be economical for small plants in the 1 million to 5 million cubic feet per day range, are expected to have a significant market.