 My name is William Tarpe. I'm a PhD student in environmental engineering and I work on reimagining urine as a resource. What really motivates me is thinking about more people getting access to toilets. In many places in Sub-Saharan Africa or across the developing world, not having access to a toilet causes a lot of problems in a person's life. From general cleanliness to a host of diseases that are transmitted from person to person. But we can help solve this problem by making fertilizer from urine. If we create fertilizer from urine and we sell it, that money can be used to build more toilets. We've seen that we can cut the cost of fertilizer and we hope that that can make food more accessible in these regions. Urine is great because it has a lot of the nutrients that come out of a toilet. Those nutrients are nitrogen, phosphorus and potassium and those are the same nutrients that are in fertilizers that we use on crops all around the world. So the big question is how we extract nitrogen from urine. We do that using this. It's an electrochemical cell. We start with urine in a bottle like this. It goes from this bottle into this first chamber. In the second bottle we start with water and it goes to this second chamber. This nitrogen that's in this urine will cross this membrane from chamber one to chamber two. So in order to get this nitrogen to move, we need to introduce electricity. That electricity is what pushes the nitrogen to move as well. Now we have nitrogen present in chamber two. It's positive ammonia, NH4+. The electricity also introduces hydroxide ions. That makes the nitrogen change form from NH4+, to NH3. NH3 is a gas. Now we have a membrane that selects for gases. We leave the liquid behind and only gas can get through. That nitrogen is a gas that's mixed with water to capture it and now we have the liquid fertilizer. That's it. As we're making the technology in the lab, we're also doing field visits to Nairobi, Kenya. There's a company in Nairobi called Sanergy that we partner with for our research that makes toilets for people. Once the waste is collected, it goes to a waste treatment plant. When I was in the field, sometimes from my experiments, I would collect the urine myself and take it to the treatment plant. Inside the lab I would use things like a pH probe to test how acidic or basic the urine is. I would also measure nitrogen to track it through the system. We can make about three pounds of fertilizer from one person's pee in a day. Now if you multiply that by a city, a region, a nation, we can make a lot of fertilizer. If we're successful, we can potentially help the hunger crisis across the world. I envision a day where everyone have access to a toilet because I believe it's a basic human right that can really improve individual lives and our collective society.