Sustainable Energy Usage
The tremendous gain in production efficiency from modern technology allows cotton growers to produce almost two times more cotton worldwide now than in the 1960s on essentially the same amount of land, resulting in more cotton out for the energy put in. At the same time, reduced tillage practices now in place reduce fuel use on the farm. Based on recent data for all energy used in U.S. cotton production (direct energy in the fuel tractors and all the energy "embedded" in the fertilizer and other inputs) is about 50% less than the gross energy content in the cottonseed that was also produced with the fiber.
The Cotton Energy Balance
There has been a great deal of attention given to the "energy balance" of agricultural production, especially in relation to biofuel crops such as soybeans for biodiesel and corn for ethanol. The energy input considers obvious factors such as the amount of fuel used by agricultural equipment, but also includes the energy associated with the manufacture of inputs into the system such as fertilizers and crop protection products. These methods have been applied to cotton production in three different studies for cotton grown in the US resulting in a range of 14 to 35 GJ of total energy per metric ton of fiber produced, and average value of 19 GJ per ton. (1 GJ of energy is approximately equal to the energy contained in 7.5 gallons of gasoline. One metric ton is 2205 pounds).
The full energy of cottonseed has to be adjusted to account for its being processed into fuel. Notwithstanding, the oil alone from the seed can generate almost 20 gallons of biodiesel per acre, and that does not take into account the energy content represented by other parts of the plant. If cottonseed were converted to energy at an efficiency of 60%, the net energy requirements to produce an average bale of cotton in the U.S. is essentially zero.