LAUSR

Abstract It is necessary to review the reactive nitrogen cycle, from its generation to its emission to the environment, because it is intimately connected, as either a problem or a solution, to food security, environmental degradation, climate change and alternative energy. These connections are not often appreciated because the researchers in these disparate fields of scientific investigation do not interact extensively. This paper intends to fill that gap by presenting a broad overview and offering an important perspective on this important substance. It is well known that the global food supply depends on anthropogenic nitrogen fertilizer and that its production and overuse has contributed to the deterioration of the environment. This paper points out that biofuels production and carbon capture schemes may also increase demand for reactive nitrogen. In addition, ammonia is being proposed as an alternative fuel. Although the exact magnitude of future requirements is uncertain, a large demand for reactive nitrogen may be inevitable and recovery from waste must be pursued. However, the recovery of reactive nitrogen from waste streams is imperfect because natural processes tend to return reactive nitrogen to the more stable state, N 2 . Thus, new technologies to replace the Haber–Bosch process must be developed. This paper reviews these new technologies and shows that almost all of the alternative means for producing reactive nitrogen are in early development. Intensified efforts to develop scalable alternatives are recommended.