Ever wonder what happens after you flush the toilet? Well, the 7 liters of water flushed through the toilet push your waste into the sewage system. In the US, this is usually either sent to a treatment center or just mixed with rainwater and released into the waterways. If it is sent to a treatment center, usually it is treated just enough so that it can be used as fertilizer on cropland, but we don’t really know how this affects human health. So although we westerners may think we’ve solved the sanitation issue (and we have in comparison to much of the developing world), there’s still a lot that can be done. Over at Nature they outline four different ‘eco-friendly’ toilet designs to help eliminate some of our sanitation issues. They’re all pretty interesting, so go check them out!