Nitrogen is the biggest bottleneck in post-fossil-fuel food production. Before the advent of the Haber-Bosch process, which compresses atmospheric nitrogen (N2) and hydrogen (H2) into ammonia fertilizer (NH3), nitrogen was harvested everywhere it could be found, from remote islands covered in bird droppings (even leading to a war) to domestic dung heaps. Surprisingly enough, the … More Homemade Plant Fertilizer: Urine + Ashes