TedPage: Energy from the Sun

Over on Real Climate they're discussing a report in Nature that plants can emit methane. While I understand there is effect on the global warming models, why aren't people looking at this as a potential energy source? If a plant could create methane and oxygen, which we could then burn, it would seem like a pretty green source of power. The burning of the methane could power a generator, sounds like a solar cell to me. Of course, my excitement could be caused by not understanding the process used to get the methane -- but I can't read the Nature article to find out.