Methane hydrate is basically natural gas locked up in ice. Actual, commercial-scale production of gas from these formations has never been accomplished, but the DOE's success here might open the door to the industry. The method the DOE used was novel: carbon dioxide was injected into the hydrates, where it was exchanged with the methane molecules locked up in the ice. Using this technique, they were able to extract natural gas continuously for 30 days. The previous longest run was six days.
If methane hydrate production becomes cheap and easy, it could change the global energy picture dramatically. The exact amounts aren't totally clear, but around the world there could be more energy locked up in hydrates than in all the rest of the planet's fossil fuels combined. Of course, burning all of it wouldn't be great for the climate, even if natural gas is a bit better than coal in that regard. And some think that methane hydrates might melt on their own as the climate warms, releasing a gas that is more than 20 times as potent as a warming agent than CO2.
The DOE says the next step is to test methane hydrate production over even longer periods of time, with the goal of bringing costs down into the economically-viable range. This process, though, "may take years to accomplish." Along with its own tests, the DOE is also offering $6.5 million in funding this year research into methane hydrate extraction technology, and is asking for another $5 million from Congress to add to the effort next year.