Outline
Half the carbon dioxide emission levels of petroleum or coal on combustion
One of the most promising candidates for an efficient natural resource to help in the fight against global climate change is available in large quantities under Japan’s territorial waters.
Methane hydrate—or burnable ice, as it is sometimes called—is found as crystalline solids, comprising a cage of water molecules, inside which a methane gas molecular is located.
Burning this methane gas produces energy. From around 1m³ of methane hydrate, approximately 150–170m³ of methane gas can be generated. Methane gas, in turn, has a much higher combustion efficiency than natural gases. Herein lies the key to the scale and efficiency of the energy we can glean from methane hydrate.
Methane hydrate is found mostly in sea beds where pressure is high and temperature low. Generally, it is found in large quantities in continental sloops facing ocean trenches. The Japanese archipelago is surrounded by such sloops, and as such is a rich source of methane hydrate. Estimates put the amount of methane hydrate available in the oceans surrounding Japan the equivalent, in energy terms, of one hundred years’ worth of natural gas consumption at present levels.
If the development of methane hydrate as a commercially viable natural resource continues along its current, promising, trajectory, then resources-less Japan will have found itself a bounty. Moreover, since the technology required to generate practically-usable methane gas from methane hydrate deep under seas is extremely high-level, Japan may also be able to export the technology it develops to exploit its natural methane hydrate reserves.
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Methane Hydrate as a Commercially Viable Energy Resource
The key to developing technology that will allow the utilization of methane hydrate as a commercially viable resource lies in being able to maximize the amount of methane gas that can be extracted from the methane hydrate. Methane gas is extracted by breaking down the methane hydrate within the seabed sediment into water and methane gas. This process requires extremely high-level technology.
Petroleum or natural gas will rise to the surface by itself once a hole has been drilled to the source. Coal, which is stable solid, is collected in lumps. But methane hydrate is found within seabed sediments, and in between grains of sand. It is not possible to filter out only the methane hydrate grains in the same way that it is possible to filter out coal from rocks. Moreover, the methane gas extracted will return to a crystallized state if subject to high pressure and low temperature.
Such properties had previously lead scientists to conclude that methane hydrate was simply not a practicable resource in terms of the high cost required to extract and utilize the methane gas contained within.
Moreover, those countries rich with other energy resources, such as petroleum, coal, and natural gas, were more focused on how they would use the resources they already had, rather than prioritizing potential future energy sources.
Japan, however, is an energy resource less country, a fact that prompted the implementation of research into the commercialization of methane hydrate significantly earlier than other countries. Indeed, most of the surveys and research carried out into methane hydrate so far has been conducted by Japan.
Today, hopes are high that technology developed and honed for the extraction of natural gas can be applied to methane hydrate, depending on its state, and Japan boasts significant advantages in this field.
The Development of Methane Hydrate Technology in Japan
In Japan, the Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry spearheaded a development plan for methane hydrate in 2001. The plan resulted in extensive surveys being carried out on the remaining volume of methane hydrate in the seas around Japan and the rest of the world, as well as test diggings and extractions in those regions thought to be rich in methane hydrate deposits.
In 2002, the ‘hot water circulation method’ was used to generate methane gas from the methane hydrate layer; this was the first such successful attempt anywhere in the world. In 2008, the ‘reduced pressure method’ was used in the successive generation of methane gas; this proved the efficacy of the technique as a production method. This was another world first for the Japanese scientists involved.
Going forward, scientists and researchers will continue to work on the next stage of developing, seeking to improve technology in order to reach commercially-viable output levels, as well as establish developmental systems capable of responding to environmental risks.
March 27, 2012
About the author
Hiromi Jitsukata is a reporter for Japanest NIPPON
