Here's a somewhat funny and completely useless piece of thinking. One of these days, my older son asked me whether at any second, somebody is going to the loo. I answered yes, and certainly a lot more than only one person. Then it got me thinking.
If we assume there are 7.6 billion (7.6E9) people on earth,
everybody has to pee 3 times a day, and peeing takes 10 seconds,
then on average there are
7.6E9 * 3 * 10 sec / 86400 sec = 2.6E9
or more than 2 million people peeing each moment in time.
Further assuming during those 10 seconds, each person is peeing 0.2 L,
the resulting stream is
2.6E9 * 0.02 L/sec = 5.2E4 L/sec
or approximately 52 cubicmetres per second.
With Earth's mean temperature of about 15 degC, and the temperature of
the human body at about 37 degC, resulting in a difference of about 20 K,
and assuming pee has the same density of
1000 kg/m3 and specific heat
4.2 kJ/kg/K as water, this represents a thermodynamic power of
52 m3/sec * 20 K * 4.2 kJ/kg/K * 1000 kg/m3 = 4.4E6 kJ/sec = 4.4E9 J/sec
i.e over 4 Gigawatt — about twice the installed power of the
Aswan hydroelectric power plant