There will be many ways to make ammonia in the future and, regardless of breakthroughs in chemical catalysts and engineering design, genetically modified organisms will play an increasingly important role.
At this week's American Chemical Society meeting, Daniel Nocera from Harvard University introduced his new ammonia synthesis technology. It builds on his "artificial leaf" that produces and stores hydrogen using power from sunlight. Nocera's latest innovation is to couple this system with a microbe that naturally contains nitrogenase, the enzyme that fixes atmospheric nitrogen into ammonia.
The end result - a robust population of nitrogen fertilizer-emitting microbes - can be delivered to the soil simply by watering the plants.