As if all the other natural-resource problems facing the planet weren't enough, apparently now there's a feces crisis, too. At least that's what Johann Hari argues after reading Rose George's The Big Necessity, which says that the world is facing a (literal) shit storm of epic proportions:

Much as we want to flush and forget, the excrement does not disappear. Ninety percent of the world's sewage ends up untreated in oceans, rivers, and lakes. The costs of Joseph Bazaglette's invention—at the other end of the pipe—are now becoming inescapable. Much of our sewage is pumped, barely treated, into the oceans, where vast dead zones are emerging, killed by our germs.

The rest infests water closer to home. For example, in 1993, an outbreak of shit-borne cryptosporidium in Milwaukee killed 400 people and made 400,000 sick. It turned out the city was pumping its "treated" sewage—actually treated for only some toxins, not others—into Lake Michigan and then slurping its drinking water out the other end.

OK, setting aside the fact that dead zones are caused mainly by nitrogen fertilizer runoff, not wastewater overflow, there's something to this: The world does create a lot of crap, and managing it is difficult. Here are a few approaches: Some 15 million Chinese homes have biogas digesters, where you dump your, um, dump and it ferments into a gas that can be converted into electricity. That's promising, but limited in use, since you need a steady supply of animal feces to keep the plants running. Human waste is also difficult to convert to fertilizer, although, contra Hari's suggestion that it's impossible, New York City actually has a plant that converts sludge to fertilizer pellets, plopped down in (where else?) a poor neighborhood in South Bronx. (The smell, if you're curious, is horrifying.)

Then, of course, there are Western sanitation methods, which hold up admirably, but also use massive amounts of energy and water in a world where both are becoming scarcer. (You need one coal plant, for instance, to run just four sewage treatment facilities.) So George has proposed a rather... unorthodox alternative:

First, we have to change our toilets—and our sewers—so they have two streams: one for urine and another for excrement. Although it's counterintuitive, urine actually contaminates sewer water much more severely than feces do. If it ran into a separate system, we would slash water use by an extraordinary 80 percent. The second prong is harder to imagine. As in presewer London, we would defecate into a tank, and our shit would sit there waiting for collection.

I've seen similar proposals elsewhere, and frankly, they're hard to imagine, though I guess it's true that toilets have changed pretty dramatically over the past century, and could change again if need be (when I was a kid growing up in Tokyo, there were still plenty of hole-in-the-ground models in public restrooms, though those seem to be dying off). Still, radical eco-solutions like these might be jumping out too far ahead—many poorer countries haven't even started on a halfway decent sewage-management systems, and that would seem like priority number one, no?

--Bradford Plumer