In the section of this chapter about transportation of fossi

In the section of this chapter about transportation of fossil fuels, I pointed out that humankind uses about 500 EJ of energy each year, nearly all of them fossil fuels, and that energy content of fossil fuels is around 30 to 60 MJ/kg. (a) Using an approximate figure of 40 MJ/kg, estimate the total mass of fossil fuels we burn each year. (b) Assume that each kilogram of fuel has to be moved 1,000 km from its source to where it’s burned (more for imported oil, less for some coal), at an average speed of 20km per hour. Estimate the total mass of fuel that must be in transit at a given time.

Solution

a)

Energy used each year,

E = 500 EJ = 500*10^18 J

Energy of fossil fuel:

Ef = 40 MJ/kg = 40*10^6 J/kg

So, mass of fossil fuel used:

m = E/Ef

= 500*10^18/(40*10^6)

= 1.25*10^13 kg

b)

Each kg of fuel has to moved 1000 km

average speed = 20km/h

So, time taken per each kg of fuel = 1000/20 = 50 h

So, total mass of fuel in transit = (1.25*10^13 kg/yr )* 50h

= 1.25*10^13*50/(365*24)

= 7.13*10^10 kg