Unlocking the biofuel energy stored in plant cell walls

By virtue of their chloroplasts, plants are superb harvesters of solar energy. They use it to build leaves, flowers, fruits, stems, and roots. We harvest a small percentage of that energy in the form of food and a smaller amount in the form of wood for heating.

But the vast majority of plant biomass goes unused by us. In every agricultural region on Earth, huge amounts of the structural parts of crops -- things like cornstalks, sugar canes, beanstalks, and wheat stems -- are discarded because we haven't figured out a way to convert them into fuel.

In underground caves and equally extreme environments, Jenn Macalady finds analogs for life on other Earths

The first time she entered Italy’s Frasassi Caves, Jenn Macalady gave her husband a scare. “He was waiting for me to come out,” she remembers. “I was so amazed by what was down there that I lost all track of time. I was completely enthralled.”

Frasassi, discovered in 1948, is one of the show caves of Europe. The 19-mile subterranean system comprises one of the largest and most spectacular limestone complexes in the world, drawing thousands of visitors every year. But it wasn’t the stalactites and stalagmites that captured her. Macalady, a geomicrobiologist at Penn State, was more interested in the slime.