It works simply: You put the dog poop into the large container, where it is digested by bacteria, creating methane gas, which can then be used to light a lamp. Biogas digesters like this are often used on landfills or for large amounts of cow manure, but it's unusual to see it on such a small, human scale.
Dog parks, as you know if you've ever been to one, create a lot of excrement. This new street light both helps people connect their actions to the larger power system (poop in equals power out). But more importantly, it highlights the idea that there are potential energy sources all around us. If we're going to use much less oil, there isn't going to be a one-stop solution. It will be a combination of every available scrap of energy, from wind to solar to, yes, dog poop.
Photos by Matthew Mazzotta.