Table 7. Estimated carbon payback time for jatropha.


Scenario (tons oil/ha/yr by 6th year of production) Oil production over 10 years (tons/ha) Carbon
Equiv. of oil produced (tons/ha)
Carbon inputs over 10 years (tons/ha) Net change in carbon in biomass (tons, over 10 years) Net annual balance, averaged over 10 years (tons C/ha/yr) Payback period (years until positive balance is reached)
Acahual < 5 years old
5 35 30.05 8.8 + 5.5 2.67 2
3.4 23.8 20.4 8.8 + 2.5 1.41 3.5
1.7 11.9 10.2 2.6 −0.5 0.75 6
Acahual 6–10 years old
5 35 30.05 8.8 + 2.0 2.33 7
3.4 23.8 20.4 8.8 −1.0 1.06 8
1.7 11.9 10.2 2.6 −4.0 0.36 11
Acahual > 15 years old
5 35 30.05 8.8 −20.0 0.17 14
3.4 23.8 20.4 8.8 −23 −1.08
1.7 11.9 10.2 2.6 −26.0 −1.84

Scenarios with 5 tons oil/ha/year after 6th year assume fast plant growth and high level of inputs. Scenarios with 3.4 tons oil/ha/year assume average growth and high level of inputs. Scenarios with 1.7 tons oil/ha/year assume moderate growth and low inputs. All scenarios assume build up of oil yield in first 5 years as shown in Table 4.