Sanitation doesn't get a lot of headlines but, all told, its absence kills 6,000 children a day, according to British charity Water Aid. And the solution chosen by the developed world—the flush toilet—is running up against limits in the amount of water available to flush away human waste.

The United Nations has attempted to fill this gap by securing a pledge from developed countries to halve the number of people without any form of sanitation—whether basic outdoor latrines or indoor toilets—by 2015 as part of  its Millennium Development Goals (a series of goals for world development, ranging from alleviating poverty to fighting diseases like AIDS). To accomplish this task, however, a toilet would have to be installed every second between now and then, according to the U.N.

As a result, this objective may be the furthest of these goals from being realized. At present rates of progress, sub-Saharan Africa, for example, would only reach the target by 2076, according to Water Aid. And the developed world is in no better shape: U.S. Environmental Protection Agency estimates predict a $122 billion spending shortfall on wastewater treatment necessities between 2000 and 2019.

In an effort to better understand this sanitation crisis, Scientific American's David Biello spoke with Rose George, author of The Big Necessity: The Unmentionable World of Human Waste and Why It Matters. (Read an excerpt here.)

What inspired this book? Why toilets?
It was kind of a gradual process. … I was introduced to Dr. Bindeshwar Pathak of Sulabh [a non-governmental organization devoted to sanitation] in India. He was a Brahmin [member of the highest Hindu caste] who devoted his life to saving untouchables [the lowest caste] from the horrible job of cleaning dry latrines with their bare hands. His life's work was installing half a million public toilets, which American tourists have probably enjoyed.

Right now, 2.6 billion people have no toilet, not even a bucket. That's four in 10. And diarrhea kills more children under five than TB, HIV and malaria combined. I found that absolutely shocking. And I found these people who I came to admire, kind of sanitation foot soldiers like Dr. Pathak, trying to do their bit. It's a colorful cast of characters. Dr. Pathak also set up the International Museum of Toilets—the biggest toilet museum in the world—which is one room in New Delhi.

So what's the biggest sanitation challenge?

One is to get people to have and to use a toilet. The other is to get the issue into public discourse. To get people to dare [to] talk about sanitation and toilets. To get them to be at ease talking about sanitation and clean water.

Clean water seems to get more attention.
Sanitation and clean water can't be separated. Up until now, the world attention and money has been going to clean water. There's little point in installing clean water when people are contaminating that water by doing their business in or nearby it. They can't be separated but they are. That might be changing but slowly.

How is it changing?
It's the international year of sanitation. Did you know that? Of course, U.N. years are kind of meaningless. There are all sorts of years and decades. The 1990s was the Third Water Decade, and we're now in the Water for All Decade. It's kind of meaningless, but this time there is also real momentum. The Prince of Orange, who is a top sanitation advisor for the U.N., is one of quite a few royals, actually, willing to get his hands dirty talking about sanitation. There's movement towards the idea that it's okay to talk about human waste. Matt Damon is talking about latrines. We need a celebrity champion like that. So far, they mostly want to stand next to a shiny new tap rather than a not-so-nice shiny latrine, though statistically the latter is more important. [Matt Damon] seems to be making the logical connection that you can't have one without the other. Maybe he'll come around and be photographed in front of a latrine.

Language is also a big part of the problem. We just don't have a neutral word. So the sanitation activists are looking to the HIV activists who faced the same problem. They couldn't say sex or talk about sex in conservative cultures. We need a neutral word. The plain-speaking Indians like to use the word "shit" because they're just happy with it and because their sanitary situation is so dire. In the U.S., we can say human waste but it needn't be waste. It can be a good fertilizer.

So what can be done with all this human waste?
At the moment, there isn't some great systemic solution. But there are lots of initiatives around the world, little beacons of light. In the developing world, China's biogas program is fantastic: 15.9 million household biogas digesters. China has always been quite at home with human waste, they used it raw on the fields for 4,000 years. You can still smell that when you drive around rural China. They're interested in setting up biogas, because it's an inexhaustible supply of energy. You hook up a latrine, digest the waste in an underground tank and cook with the gas it produces. And it makes a good fertilizer, which is essential now with the price of artificial fertilizers going through the roof. … But it has to be made safe because putting raw feces on crops is not a good idea.

In India, on the other hand, there's so much public defecation that it's a public health hazard. So there they are trying "Total Sanitation," where they're aiming to make areas open defecation free, rather than just construct toilets. They need to make people want a toilet not just give them one. If you do that, they won't necessarily use it. They've got a nice bush out back and they're not going to use the new government latrine, they're going to turn it into a goat shed. So advocates go to villages and appeal to their psychology.

For example, in Benin [in Africa], people's reason for finally having a latrine—even among mothers who know their children were getting diarrhea, even they were not receptive to the doom and gloom approach of health messages—they wanted them because it made them feel royal.

In India, they appeal to people's disgust by confronting them with the fact that open defecation means people are tramping shit back into the village and, horrifyingly, eating it. Once they see this with fresh eyes, they will immediately go off and build a latrine on the spot.

Also, they have a clean village campaign. You get a prize if a village achieves 100 percent total sanitation for every family, because if you have even one family still doing open defecation it contaminates the village for the rest. So you appeal to disgust and pride. It seems to be working brilliantly.

What about the sanitation solutions we do have? What are the problems with those?
Water-borne waste sewage and sewers was an excellent solution in the 19th century. But infrastructure is pushed to capacity. The design itself is flawed. It's really silly to take clean drinking water, throw filth in it and spend millions of dollars as well as lots of energy cleaning it again, especially when water is becoming quite short in supply.

Most of these systems are combined systems. They take the rain and everything that goes down toilets. An inch of rainfall or less can overwhelm them and then they do a perfectly legal discharge into the nearest river or sea. In 1993 Milwaukee had an outbreak of cryptosporidium [a parasite that causes diarrhea and results from inadequately treated water supplies] and more than 100 people died. There isn't enough money to clean all this sewage.

Is there a way of alleviating pressure at the source? Ecological sanitation advocates have this dream of everybody having a composting toilet and putting safe compost out with their recycling. That's not realistic.

So what are some intermediate steps?
Low-flush toilets that use less water. Vacuum toilets, like the ones you get on a ship or a plane that make that shoop sound, are good. But so far they're not cheap. I don't have a magic bullet solution.

Anything else to add?
I have no particular fascination with the substance itself. I don't like it anymore than the next person. The thing about shit, the reason it smells, at least according to the London School of Hygiene, is because it can be so toxic and carry so many diseases. We're not going to be able to overcome that.

But the first step is to put the issue out there and talk about it. The conversational taboo is such a big impediment. With the flush toilet, we've been able to flush [sanitation as an issue] out of our minds as well.