Cotton & Natural Resources

• Overview
• Soil
• Cotton and Water
• Impact on Habitat & Biodiversity
• Air Quality
• Energy

Energy

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. ^[1] 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. ^[2]

• Energy Resources
• The Cotton Energy Balance
• Trends in Agriculture and Energy Resources

Energy Resources

By the most optimistic estimates, the world’s petroleum reserve will be depleted in 100 years; ^[3] therefore, even with recycling, it is difficult to label synthetic fibers “sustainable”. Unlike synthetic fibers, cotton is natural and renewable.

In addition to producing fiber, cotton also produces seed. About 700 pounds of seed are produced for every bale of fiber (a bale is 480 pounds), and like other oil seeds, can be converted into biodiesel ^[4] and animal feed co-products. For typical yields in the U.S., seed production can result in over 20 gallons of biodiesel per acre – more than meeting its direct fuel use in growing and ginning the crop. ^[5] There are other indirect energy costs associated with the inputs used in cotton production, particularly fertilizers and materials used for crop protection; however, even when all energy inputs are accounted for, the total energy for cotton production is less than the gross energy content of the seed (see section on “Cotton’s Energy Balance”).

Fuel pump for biodiesel fuel

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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 tonne. ^[6] (1 GJ of energy is approximately equal to the energy contained in 7.5 gallons of gasoline.  One metric ton is 2205 pounds).

The gross energy of cottonseed produced with that tonne of fiber far exceeds the energy needed in the production as illustrated in the figure below. ^[7]

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. ^[8]   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.

Total energy input (excluding solar energy capture by the plant) to produce a metric ton of cotton compared to the total energy content of cottonseed produced with the fiber.

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Trends in Agriculture and Energy Resources ^[9]

On-farm energy management has a huge potential for improving the environment, lowering farm and ranch production costs and decreasing reliance on foreign energy supplies. Cotton producers are implementing many of the energy conservation steps recommend by the Natural Resources Conservation Service (NRCS), including:

• Reducing or eliminating tillage and managing residues to reduce fuel use and improve soil, water and air quality. Switching from conventional tillage methods to no-till can results in fuel savings of 3.9 gallons per acre.
• Adjusting nutrient management and crop rotations to include legumes to offset use of petroleum-based nitrogen fertilizers.
• Adjusting irrigation timing to directly reduce energy consumption as well as other resource concerns.
• Using integrated pest management strategies to optimize petroleum-based inputs and to produce environmental benefits. With precision application, better weed control, lower herbicide runoff and energy savings of 45 percent are being realized.
• Planting perennial crops and introducing rotational grazing to reduce energy associated with planting and harvesting.
• Switching to more energy-efficient machinery such as irrigation pumps. Improvements in water efficiency of a modest 10 percent could reduce diesel consumption by 80 million gallons or $192 million dollars on irrigated farmland.
• Converting to biofuels, such as ethanol and biodiesel, to directly reduce demand for petroleum-based liquid fuels as well as to potentially improve air quality.
• Recycling lubricants and other petroleum-based material to reduce demand for petroleum and to reduce potential environmental damage associated with other disposal means.
• Developing alternative energy sources, such as anaerobic digestion, solar and wind, to directly substitute for purchased energy supplies and reduce carbon and greenhouse gas (GHG) emissions.

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