Burn baby burn
Let’s say that in our hypothetical system, we have an artificial pancreas that produces enzymes that are able to break down dietary fibers into sugar molecules. Our poop-extracted fiber will, for the sake of simplicity, be completely converted into burnable glucose by these enzymes.
So, at this point, this means that we have 7.5 grams of glucose per poop. Glucose burns in a plentiful oxygen supply to produce thermal energy, water, and carbon dioxide. Per gram, it produces 14.2 kilojoules of energy. This amount of poop-extracted goodness will therefore produce 106.5 kilojoules of energy.
The current population of the world is 7.125 billion. If they all had a 100-gram poop, the 7.5 grams of fiber could be removed and converted into glucose, and if this glucose was burned, this would produce a total of 759 billion kilojoules of energy every single day. In a year, this would total roughly 277 trillion kilojoules of energy.
Based on information given by the US Energy Information Administration, the annual electricity consumption for the average American home was 39.4 million kilojoules in 2014. This means that our poop-powered electricity engine could power 7.03 million US homes every single year.
That may sound like a lot, but considering that we’re using all of the human poop in the world here, that’s not much at all. There are roughly 125 million households in the US alone, so the global poop production would fuel just 5.6 percent of all US households.