In the search for alternative hydro carbon energy sources attention is turning to one of the most abundant organic compounds on earth Methane. Compared to other hydrocarbon fuels, burning methane produces less carbon dioxide for each unit of heat released therefore making it a relatively clean energy in comparison to petrol or gasoline.
Emissions from engines fuelled by compressed natural gas are 10 per cent lower than those from a petrol engine. (Methane is the major component of natural gas, about 87% by volume.) However, about 30 per cent more fuel is needed to maintain a vehicle’s range. That requires fatter, heavier, high-pressure fuel tanks, which eat up space, dent fuel efficiency and increase the price of the car.
However a possible solution has recently been unveiled, a new kind of fuel tank inspired by the human intestine which could make cars running on methane much more attractive to motorists.
The space-saving notion, developed by technology firm Otherlab of San Francisco, with funding from the US government’s energy research arm, ARPA-E, copies the way the human body maximises storage capacity by folding the intestines back and forth. Instead of one large, high-pressure tank there are multiple banks of thin, pressurised metal tubes that can be bent and distributed all through the car, from the inside of the wheel arches to the roof supports and front wings.
A possible source of the methane needed to power future vehicles like this has also recently been located just off Japan‘s south-west coast, 1300 metres below the surface, a huge cache of slushy, combustible ice lies buried in the ocean floor. This month, Japan is carrying out the first offshore attempt to produce methane gas from these frozen methane hydrates. If successful, this could be the next great energy source.
Methane hydrates consist of methane molecules trapped in a cage-like structure of water, they are abundant in ocean floors around the world and under Arctic permafrost. It is estimated that the total energy of the planet’s hydrates is greater than all other energy sources combined. The US, India, South Korea and Russia all have programmes to explore the potential of hydrates, but the on-going natural gas boom makes it a low priority for now.
Japan is the exception, as the world’s largest importer of natural gas and with concerns about continued use of nuclear energy. It has invested hundreds of millions of dollars in hydrate research, especially in the Nankai trough off its Pacific coast. The area may hold enough gas to meet the country’s energy needs for a century.
This month, a team led by the Japan Oil, Gas and Metals National Corporation will drill 300 metres below the seabed, and place a pipe to carry methane to the surface. The goal is to produce tens of thousands of cubic metres of gas over about two weeks. Commercial production could start in 2018.
The Japanese team will monitor sea floor movement during their test, particularly watching for landslides. They hope this will help them calculate how much gas can safely be extracted over a larger area, and how fast.
Richard Charter, who sits on the DoE’s hydrate advisory committee, worries that large-scale mining could cause greater unforeseen impacts, like small earthquakes or an uncontrollable gas release that would escape into the atmosphere or acidify the waters around the borehole. “You’re basically punching a hole into a zone we don’t know about,” he says.
Tetsuya Fujii of the Japan Oil, Gas and Metals National Corporation says deep-sea hydrates have a built-in fail-safe: if the pipeline breaks, the water pressure would make the hydrates recrystallise, helping to stem the leak. Any gas that did escape would dissolve in the water column or be eaten by bacteria.
Sources include New Scientist and Wikipedia
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