Of course, the meat we consume, and the nitrogen we excrete in waste, is not the only concern. Another important problem is that our agricultural practices, in general, and the production of meat in particular, are remarkably inefficient. Of the 170 million metric tons of nitrogen (the equivalent of more than one and a half million blue whales) humans apply to cropland, only 12% actually ends up in our mouths (Galloway et al. 2003). In other words, it takes 100 kg (220 lbs) of nitrogen in corn to produce 5 kg (11 lbs) of edible nitrogen in beef — but the remaining 95 kg of nitrogen is lost to the surrounding environment (Nixon and Fulweiler 2009).