When the BBC showed us insane amount of cyclists it takes to power a home, it prompted much discussion about "energy slaves"—or the idea that fossil fuels have replaced tasks that would previously have needed to be done by hand. But just how much human labor does gas replace? In an interview with The Nation about peak oil, Rob Hopkins of the Transition Network suggested that 1 litre (he is British) of gas replaces 35 days of human labor. Walter Haugen took issue to his numbers over at Local Harvest, claiming he overstated the energy value of gas by a factor of four. Either way, we know gas does a lot of work so we don't have to. We'll have to find that energy from somewhere, or stop using it, when the black gold runs out. We can't feed the world on volunteerism alone.