sustainability - SUNY College of Environmental Science and Forestry

Sustainability 2011 , 3 2378

Figure 2. Energy return on investment of wheat and rice produced in Pakistan and the

percentage change in the EROI from the previous year (1999–2009). Percentage change

figures at the top of the figure are for rice and in the middle of the figure for wheat.

Table 12. Regressions-fiscal year vs. wheat EROI.

Regression r^2 value Adjusted r (^2) value p-value Residual sum of squares Equation
Linear 0.40 0.33 0.0367 0.28 y = 85.07 − 0.04098x
Quadratic 0.50 0.37 0.0639 0.23 y = 29,061 0.007215x 2 − 28.96x +
Cubic 0.54 0.34 0.1257 0.21 10.33xy = −13,814,792 + 20,695x (^2) + 0.00172x 3 −^
Quartic 0.61 0.35 0.1702 0.18
y = − 14,407,445,048 +
28,750,586x − 21,515x^2 + 7.156x^3
− 0.0008924x^4
0.0
1.0
2.0
3.0
4.0
5.0
6.0
1999 2001 2003 2005 2007 2009
Rice
Wheat

• 1.4% - 3.1% - 22.3% 7.0% - 15.3% - 0.1% 21.8% - 4.3% 16.1% 15.4%

11.5% - 9.9% - 5.1% 2.9% - 6.1% - 1.9% - 2.9% 13.9% - 12.8% 9.1%

Energy return on investment

Time (fiscal years)

G