Ammonia

The second-most produced chemical in the world, ammonia's molecular structure is a single nitrogen atom bonded to three hydrogen atoms. It's used in huge volumes in agriculture, among other industries, and current production techniques are dirty and energy-intensive, using about 2% of the world's fossil-fuel energy and producing around 1% of total global man-made greenhouse emissions.

Ammonia has considerable potential as a clean fuel, storing more than 20 times as much energy by weight as today's lithium batteries. A lot of current research is focused on new totally clean production methods, as well as on new ways of extracting energy from ammonia as a potentially clean way to power long-haul ships and trucks.