ABSTRACT

The aim of this study was to compare some of the most common growing practices in terms of yield, cost and environmental impacts. Generally the applications of fertilizers, pesticides and auxiliaries show significant impacts on costs and the quality of the harvested fiber as well as on the environmental impacts. Relevant effects and stages of cotton production are pointed out to allow comparison of the environmental impacts of cotton production with impacts of other textile production steps as well as other fiber textile materials. Among a great variety of applied practices five cotton cultivation scenarios were selected, based on the same variety HS 26 to be investigated and compared by means of LCA. Particular interest was put on irrigation systems since they are considered to have a high impact on the environmental situation of the Texas High Plains. The scenarios are: "BDryland" (rain grown cotton), "BFurrow" (furrow irrigated cotton), "BLEPA" (irrigation with a LEPA system), "WOrganic" (with LEPA system), "WRR" (Roundup Ready with LEPA system), whereby the first initials of the scenarios indicate the farm where the cotton was grown.

Detailed data (inventories) of all scenarios was collected in 2001, and environmental impacts were assessed by means of Life Cycle Assessment with the LCA software tool SimaPro. As the functional unit "1/kg harvested cotton" was chosen. For comparison the inventory was assessed with the method of the Center voor Milieukunde (CML) (Heijungs 1992) and the "critical surface time" (CST). The last method was recently developed at the Swiss Federal Institute of Technology Lausanne (Margni in press) particularly for LCA in agriculture.

Yields ranged from 100 lbs/acre ("BDryland") to 1300 lbs ("WRR"). In our study we found the Lepa irrigated "WRR" and "WOrganic" scenarios, cultivated on the same farm as best yielding, followed by "BFurrow", "BLEPA and BDryland. BDryland cotton was the most expensive, mainly due to its low yield. However costs did not exactly show the same ranging as yield: "WOrganic" as the second best yielding scenario caused a little higher costs than "BFurrow" (the third best yielding scenario). Considering yields and cost one has to admit that 2001 has been an extreme year regarding weather conditions.
Considering environmental impacts, all investigations show that the "WOrganic" growing scenario has a very small influence on the environment compared to the other growing scenarios, as expected. In the conventional growing scenarios the active ingredients of the used pesticides lead to dominant environmental effects in the categories "terrestrial ecotoxicity" and "aquatic ecotoxicity". Of all the rated pesticides, the insecticides Fyfanon and Temik have the highest impact on the environment. The "BDryland" scenario has the highest impact on the environment in all classes, mainly because the yield was very small in 2001. Next highest impacts were caused by the "BFurrow" irrigation scenario, followed by the two "BLEPA" scenarios and the "WOrganic" with the best ecological rating. However, the difference in impacts between the same irrigation practices is huge. In the best rated scenario ("WOrganic") the lower impacts are caused by the emissions of fuel and the application of manure.

Yield proved to be the most important factor. Lower yield is not only correlated with higher costs but also with higher environmental impacts. Irrigation water, a very important resource for cotton growing, is not cost effective, and water consumption is not rated in CML method for LCA. By considering the declining level of ground water in the Texas High Plains the environmental performance of irrigation system, including the amount of irrigation water, should become more cost effective. LCA methods should be improved in order to include water consumption, based on regional differences.