A system of this type uses two energy sources, one renewable, the other nonrenewable. When the nonrenewable source is used up, the growth declines back to a steady state based on the renewable source.
- N = nonrenewable energy source
- J = steady inflow of energy
- Q = stored biomass
- K*JR*Q = part of J that goes into the system
- K3 = increasing factor of Q
- K7 = increasing factor of Q
- K8 = decreasing factor of Q
- DN = -K4*N*Q
- JR = J/(1 + K*Q)
- DQ = K7*N*Q + K3*JR*Q - K8*Q
The graph shows the changes of N (red) and Q (green) over a time period.
- A population of microbes which decompose a pile of leaves and the leaves falling from the trees.
- The world economy growing up on both fossil fuels and renewable sources.