Civilization's Future

The best source of energy is from the Sun(1). After 4.5 billion years, the best primary natural energy storage occurs with plants. These living organisms capture the Sun’s energy and store it within their bodies. Presumably their purpose is to ensure adequate energy for their survival and the propagation of their species. As long as they retain enough of the Sun’s energy, their future is assured.

We have made estimates of the amount of energy stored within all the plants and other living organisms of the Earth (2). As a means of estimating the energy availability, we can use these values and hypothesis our energy needs as in the following. First, consider the vegetation’s capture of solar energy as shown in the table below. In it, values of mass refer to dry matter.

From the above table, the total energy stored in biomass is about 32.74 zettajoules (x10²¹) while the amount of energy capture each year is 2.048 zettajoules. If we assume that all the cultivated land goes into food production, then there is 1.8857 zettajoules captured every year.

Total world primary energy consumption for 2005 was 10537.1 mtoe equivalent or about 0.44 zettajoules(4). We derive most (86%) of this energy from non-renewable fossil fuels. If our quantity of energy consumption remains at or above the 2005 level then after we completely consume all the fossil fuels, we will need 23% of all the energy captured annually by vegetation.

Presumably vegetation needs all its current NPP to maintain its own existence. If we were to allocate a quarter of the NPP for our own energy needs, can we expect the vegetation to survive?

Of interest, the proven petroelum and natural gas reserves is 13.67 zettajoules(3). From this, and knowing the rate of consumption of 0.44 zettajoules indicates a time of 31 years until their depletion if all our energy comes from them (rather than the true 60%).

(1)See Earth’s Energy Budget
(2)Global Carbon Cycle
(3)Whittaker, 1975.
(4)BPs Statistical Review

This entry was posted on Wednesday, January 10th, 2007 at 9:15 pm and is filed under Energy Resource, Solar. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.