The University of California, Irvine has been granted $1 million to develop a unique laboratory for the research of clean energy obtained from methane hydrates, an as-yet untapped source of methane gas that exists in huge quantities in some ocean-floor environments.
Methane hydrates are clathrate compounds, where the methane molecules are trapped in a lattice of water ice—hence their alternate names, methane clathrate and methane ice. They occur where methane and water are present at favorable combinations of low temperatures and high pressure. These conditions restrict clathrates to undersea locations at polar latitudes and along continental shelves, where they are distributed within the sedimentary bed.
Such environments are plentiful, of course, and so it's unsurprising that methane hydrate is thought to be abundant on planet Earth. However, as our understanding of methane hydrate formation has grown, our best guess as to the extent of the reserves has become smaller. Currently, the most conservative estimate is that there are between 500 and 2,500 gigatonnes of carbon in submarine gas hydrate deposits, the majority of which are in the form of methane.
Even at the low end, however, this is more than double the Earth's 230 gigatonnes of natural gas from other sources. According to the Department of Energy, methane hydrates are Earth's largest untapped fossil fuel resource. But quantity isn't everything; it's the size of the deposits that may one day prove commercially viable to tap that are key. This category of methane hydrates may prove to be a small proportion of the total.
Extracting methane hydrate poses certain logistical headaches, including the prevention of methane gas escape. Though shorter-lived in the atmosphere, as a greenhouse gas, methane is many times as effective as carbon dioxide (and typically ends up being oxidized to CO2 anyway). When it's used as fuel, carbon dioxide is the primary output.
The researchers at UC Irvine, led by Derek Dunn-Rankin and Peter Taborek, want to see if we could sidestep both issues. They plan on examining whether it might be possible to use the methane and sequester the resulting carbon dioxide, all at its undersea source. "There are, of course, tremendous challenges and uncertainty regarding the in situ utilization of methane hydrates, but the ultra high pressure environment of the deep ocean offers some new ways to think about clean power production," Dunn-Rankin told Ars.
To that end, the new laboratory will contain a combustion reactor vessel and a multiphase emission evolution vessel that will allow the combustion of methane from methane hydrate in simulated deep-sea conditions. "The point of the multiphase emission evolution vessel is to see how the presence of other combustion emission gases affects the CO2 capture and stability," Dunn-Rankin explained. "It is to look for the kinetics of hydrates and mechanisms that might enhance their stability." The methane hydrate used will itself be made in the lab.
So is there a plan to trap the carbon dioxide in a similar icy prison?
"It is not necessarily a new hydrate form," Dunn-Rankin told Ars. "The real issue is that if you put CO2 hydrate into surroundings that have no CO2 dissolved into them, the thermodynamics would force the CO2 to gradually try to equilibrate the surroundings—which means the hydrate would dissolve. This is shown to be the case in most laboratory tests and theory. The thing is, the methane hydrates should do the same thing and yet they are stable on very long timescales. The understanding of why this might occur, the kinetics of the processes, and the effects of small amounts of natural surfactants and other species is unknown."
The goal so far as methane hydrate is concerned, Dunn-Rankin explained, is to see if it makes any sense to use methane hydrate at the source. However, it's thought that the lab could also see use for broader energy-related research into fuel cells, obtaining hydrogen from methane, and water purification.
Given the focus of the research, we shouldn't expect that this new facility will handle all the unanswered questions surrounding the potential for methane hydrate exploitation. The role of methane hydrate in the stability of the ocean floor is not fully understood, and its extraction, by drilling or other means, may contribute to landslides on sloping sea floor. But the research does at least hint at the possibility of a more sophisticated approach to fossil fuel extraction and use.
Asked if he saw an inevitability to the use of methane hydrate as a source of energy, Dunn-Rankin's response is nuanced. "For me, the use of methane hydrate as a source of energy in the future depends more on what alternative sources of energy are available," he said. "The advances in the extraction of natural gas from shale seem to me also likely to dampen enthusiasm for more expensive and potentially riskier energy source utilization. This said, our efforts to understand hydrate dissolution and formation will always have value for the sequestration side of the problem and will allow rational considerations of methane hydrate utilization as well (we hope)."