Revised 24 May 2019

Whether any system can continue to grow or not depends on whether the system can tap a source of energy which can maintain further growth. During a period of growth when the storage of structure, reserves of energy, population, information and order are expanding, the inflows of energy into the system exceeds the outflows. In the case of humankind which is able to use large energy sources such as a rich oil well, we can tap into whatever amounts of energy that is possible to pump. When energy sources are limited, we must divide up the limited flow as shown in Figure 4. 

Figure 4: Comparison of energy sources (Odum & Odum, 1976, p47)