Compressed natural gas (CNG): An alternative to liquefied natural gas (LNG)

Natural gas is rapidly becoming an even more important resource of energy, with its share in the world consumption expected to increase dramatically over the next two decades. Currently, natural gas is transported to the markets by pipelines as LNG. Transporting the natural gas by pipelines is convenient and economically attractive onshore. For the offshore transport of natural gas, pipelines become challenging as the water depth and transporting distance increase. LNG, an effective means of transporting gas for long distances across the seas, constitutes 25% of the world gas movement. But LNG projects require large investments, along with substantial natural-gas reserves, and are economically viable for distances of 2,500 miles and beyond. CNG provides an effective way for shorter-distance transport. The technology is aimed at monetizing offshore reserves that cannot be produced because of the unavailability of a pipeline or because the LNG option is very costly. Technically, CNG is easy to deploy, with lower requirements for facilities and infrastructure. "Coselle" and "Votrans" are two would-be commercial, high-pressure gas-storage and -transport technologies for CNG. Technical and economic analyses of these two technologies were done in this study, and a comparison is provided. The results show that for distances up to 2,500 miles, natural gas can be transported as CNG at prices ranging from U.S. $0.93 to $2.23 per MMBtu compared to LNG, which can cost anywhere from $1.5 to $2.5 per MMBTU depending on the actual distance. At distances beyond 2,500 miles, the cost of delivering gas as CNG becomes higher than the cost for LNG because of the disparity in the volumes of gas transported with the two technologies.