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Natural gas can possess up to 75% to 99% methane, and its use is common throughout the world as fuel for heating, cooking, generating electricity, and powering vehicles. Other elements found in natural gas can include ethane, propane, and hydrogen sulfate. However, natural gas is a non-renewable energy source and alternatives are being sought to curb the world’s reliance on it as an essential fuel source.
The application of methane hydrates, also known as ‘fire ice’ as a new fuel source has become a popular area of interest for several countries with poor fuel economies due to the huge stores of methane hydrate underneath the sea floor. Japan, South Korea and Taiwan, among other places, are all investing in researching methane hydrate’s potential, as they have few fossil fuel resources of their own and as such are forced to spend a lot of money into importing fuel from other countries, meaning fuel prices are very steep. Methane hydrates as a fuel source is thought to be able to dwarf the potential of oil and natural gas. However, economical methods of extracting and transporting methane hydrate have yet to be developed, as most stores are found in remote areas of the ocean.
How Does Methane Hydrate Develop?
With normal atmospheric pressure levels and at room temperature, methane presents as a gas. However, when found in the presence of water at colder temperatures with greatly increased pressure levels, methane is a solid called methane hydrate. As a hydrate, the methane possesses a much higher density than that of natural gas, being approximately 160 times denser. This means that a large amount of gas can be released from the hydrate when it breaks down.
Only in areas where there is an abundance of methane can methane hydrate form. There are two ways in which this can happen, including:
Biogenic Methane
Biogenic methane develops in the sea floor when biomass breaks down, in a process called methanogenesis. When organisms die, such as krill or micro-algae, they settle on the seabed to form thick sedimentary layers. Microorganisms that produce methane break down these layers, making methane and carbon dioxide. It is estimated that 80 to 90% of methane stored in hydrates is produced through methanogenesis.
Thermogenic Methane
Thermogenic methane is produced chemically. This process occurs at far deeper layers of the Earth’s crust and does not involve microorganisms. Oil and natural gas are formed in similar ways, when biomass from millions of years ago is changed into methane by high temperatures and atmospheric pressure levels. The thermogenic methane rises through cracks in rocks until it arrives at layers in the Earth’s crust where pressure levels allow hydrates to be formed.
Where is Methane Hydrate Found?
While methane hydrate has been known about for around 80 years, it hasn’t yet found a common, economical application. The possibility of methane hydrate occurring naturally was debated until scientists accidentally discovered it underneath the Earth’s surface in the 1960s. Subsequently, it was found in large amounts on the Black Sea’s floor and near to Alaska’s coast. It has since been found that methane hydrate is present across all of the oceans, mainly on continental fringes. This is due to the fact that coastal areas are usually rife with planktonic creatures and marine activity, so biomass build up and the formation of sedimentary layers emitting methane is frequent.
How Can Methane Hydrate be Extracted?
There are several possible methods to extract methane hydrate from its source. As it is a solid, extraction methods differ to those used to extract oil and natural gas.
Water Circulation
Hot water is pumped into methane hydrate sources to get the hydrate to break down and release methane through the rising temperature.
Depressurization
Drills can be used to release pressure from methane hydrate sources, consequently releasing methane.
Carbon Dioxide Injection
Carbon dioxide is able to displace methane in a hydrate’s crystal structure, forming a stronger bond between the water and carbon dioxide molecule, which would make the carbon dioxide hydrate more stable than the methane hydrate. This stability means the methane is less likely to be released into the atmosphere. The carbon dioxide needed for this process would be obtained from power plant emissions, meaning no CO2 would be released into the atmosphere.
What are the Risks of Methane Hydrate Extraction?
Tsunamis caused by submarine landslides from the destabilization of the sea floor are a possible risk. Carbon dioxide injection is thought to lessen these risks considerably. Destruction to marine life and the environment is thought to be minimal, as most disruption is only found at the point of drilling or extraction.
Although it doesn’t remain in the atmosphere for as long as carbon dioxide, methane is still considered one of the most devastating greenhouse gases, as it is over 80% more potent than carbon dioxide. As such, the risks of large amount of methane being released into the atmosphere due to equipment failure or environmental disruption, for example, are a great concern. There is also the possibility of political issues arising around ownership and territorial rights.
Sources and Further Reading
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