I am an engineering professor, and for the past 14 years I've been teaching crap. (Laughter) Not that I'm a bad teacher, but I've been studying and teaching about human waste and how waste is conveyed through these wastewater treatment plants, and how we engineer and design these treatment plants so that we can protect surface water like rivers. I've based my scientific career on using leading-edge molecular techniques, DNA- and RNA-based methods to look at microbial populations in biological reactors, and again to optimize these systems. And over the years, I have developed an unhealthy obsession with toilets, and I've been known to sneak into toilets and take my camera phone all over the world. But along the way, I've learned that it's not just the technical side, but there's also this thing called the culture of crap. So for example, how many of you are washers and how many of you are wipers? (Laughter) If, well, I guess you know what I mean. If you're a washer, then you use water for anal cleansing. That's the technical term. And if you're a wiper, then you use toilet paper or, in some regions of the world where it's not available, newspaper or rags or corncobs. And this is not just a piece of trivia, but it's really important to understand and solve the sanitation problem. And it is a big problem: There are 2.5 billion people in the world who don't have access to adequate sanitation. For them, there's no modern toilet. And there are 1.1 billion people whose toilets are the streets or river banks or open spaces, and again, the technical term for that is open defecation, but that is really simply shitting in the open. And if you're living in fecal material and it's surrounding you, you're going to get sick. It's going to get into your drinking water, into your food, into your immediate surroundings. So the United Nations estimates that every year, there are  1.5 million child deaths because of inadequate sanitation. That's one preventable death every 20 seconds, 171 every hour, 4,100 every day. And so, to avoid open defecation, municipalities and cities build infrastructure, for example, like pit latrines, in peri-urban and rural areas. For example, in KwaZulu-Natal  province in South Africa, they've built tens of thousands of these pit latrines. But there's a problem when you scale up to tens of thousands, and the problem is, what happens when the pits are full? This is what happens. People defecate around the toilet. In schools, children defecate on the floors and then leave a trail outside the building and start defecating around the building, and these pits have to be cleaned and manually emptied. And who does the emptying? You've got these workers who have to sometimes go down into the pits and manually remove the contents. It's a dirty and dangerous business. As you can see, there's no protective equipment, no protective clothing. There's one worker down there. I hope you can see him. He's got a face mask on, but no shirt. And in some countries, like India, the lower castes are condemned to empty the pits, and they're further condemned by society. So you ask yourself, how can we solve this and why don't we just build Western-style flush toilets for these two and a half billion? And the answer is, it's just not possible. In some of these areas, there's not enough water, there's no energy, it's going to cost tens of trillions of dollars to lay out the sewer lines and to build the facilities and to operate and maintain these systems, and if you don't build it right, you're going to have flush toilets that basically go straight into the river, just like what's happening in many cities in the developing world. And is this really the solution? Because essentially, what you're doing is you're using clean water and you're using it to flush your toilet, convey it to a wastewater treatment plant which then discharges to a river, and that river, again, is a drinking water source. So we've got to rethink sanitation, and we've got to reinvent the sanitation infrastructure, and I'm going to argue that to do this, you have to employ systems thinking. We have to look at the whole sanitation chain. We start with a human interface, and then we have to think about how feces are collected and stored, transported, treated and reused — and not just disposal but reuse. So let's start with the human user interface. I say, it doesn't matter if you're a washer or a wiper, a sitter or a squatter, the human user interface should be clean and easy to use, because after all, taking a dump should be pleasurable. (Laughter) And when we open the possibilities to understanding this sanitation chain, then the back-end technology, the collection to the reuse, should not really matter, and then we can apply locally adoptable and context-sensitive solutions. So we can open ourselves to possibilities like, for example, this urine-diverting toilet, and there's two holes in this toilet. There's the front and the back, and the front collects the urine, and the back collects the fecal material. And so what you're doing is you're separating the urine, which has 80 percent of the nitrogen and 50 percent of the phosphorus, and then that can then be treated and precipitated to form things like struvite, which is a high-value fertilizer, and then the fecal material can then be disinfected and again converted to high-value end products. Or, for example, in some of our research, you can reuse the water by treating it in on-site sanitation systems like planter boxes or constructed wetlands. So we can open up all these possibilities if we take away the old paradigm of flush toilets and treatment plants. So you might be asking, who's going to pay? Well, I'm going to argue that governments should fund sanitation infrastructure. NGOs and donor organizations, they can do their best, but it's not going to be enough. Governments should fund sanitation the same way they fund roads and schools and hospitals and other infrastructure like bridges, because we know, and the WHO has done this study, that for every dollar that we invest in sanitation infrastructure, we get something like three to 34 dollars back. Let's go back to the problem of pit emptying. So at North Carolina State University, we challenged our students to come up with a simple solution, and this is what they came up with: a simple, modified screw auger that can move the waste up from the pit and into a collecting drum, and now the pit worker doesn't have to go down into the pit. We tested it in South Africa, and it works. We need to make it more robust, and we're going to do more testing in Malawi and South Africa this coming year. And our idea is to make this a professionalized pit-emptying service so that we can create a small business out of it, create profits and jobs, and the hope is that, as we are rethinking sanitation, we are extending the life of these pits so that we don't have to resort to quick solutions that don't really make sense. I believe that access to adequate sanitation is a basic human right. We need to stop the practice of lower castes and lower-status people going down and being condemned to empty pits. It is our moral, it is our social and our environmental obligation. Thank you. (Applause)