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EDIPTEX - Environmental assessment of textiles Annex 8: Data for cotton cultivation and harvest
Several references have been reviewed to find the best and most recent figures for consumption of fertilizer, insecticides, herbicides, fungicides, growth enhancers and defoliation agents (in connection with harvest), water and energy for cultivation, harvest and ginning (mechanical separation of the fibres from the seeds). Moreover, data for crop yields, waste volumes, coproducts (cotton seeds for feed, cotton seeds for oil) are important. Crop yieldIt should be noted that crop yields and consumption of fertilizer and chemicals differ a lot from country to country and even from one region of a country to another. ICAC (1993) states that the best crop yield of 1992/93 was the one in Brazil (West Minas Gerais region) which was 2,154 kg/ha, and the poorest one was in Uganda (BPA Zone) of 133 kg/ha! Therefore, we have to apply world averages, or a country/region can be selected for which the data is applied. We have chosen the latter solution as lack of data in several areas makes it practically impossible to obtain reasonable, applicable estimated averages for all data types. The calculation principles below for the US can be applied for other countries provided basic data is available. China and the US are, by far, the two largest producers, with approx. 16 per cent each of world production in 1991/92 (TAS, 1992). In 1995/96, the distribution was 20 per cent and 23 per cent respectively (Melliand, 1996). In 1992/93 (ICAC, 1993), the average crop yield in the US (four regions) was approx. 785 kg packed raw cotton/ha. Consumption of fertilizerThe following amounts of fertilizer were used per hectare: approx. 106 kg nitrogen/ha (s = 25, where s is the standard deviation), phosphorus approx. 63 kg P2O5/ha (s = 12) and potassium approx. 64 kg K2O/ha (s = 28). Or per kg packed raw cotton: 0.14 kg N, 0.08 kg P2O5 and 0.08 kg K2O. Consumption of other chemicalsAs for other chemicals, such as insecticides, there are countless different agents against countless insect species. The same applies to herbicides against weed and agents against various types of potential damage like fungus. We have decided to include a representative chemical from each of the five main categories insecticides, herbicides, fungicides, growth enhancers and defoliation agents. Table 8.1 shows some examples, and in 1997/98, they were all very common in the US (USDA, 1999). The table also states the dose per chemical (active substance). The volume indicated takes into account that the substance may be added in several operations. The dose has been converted to "per kg packed raw cotton" (g per kg). The average crop yield in the US in 1992/93 has been used for the conversion, i.e. approx. 785 kg packed raw cotton per hectare. Table 8.1 Consumption of chemicals - cotton cultivation
It is difficult to assess the dosage of chemicals. If focus is on the dose of the individual chemical, the above volumes are correct. But as cotton may be attacked by many different kinds of insect and inhibited by many different types of weed, several types of chemical will typically be used. This means that the total dose of particularly insecticides and herbicides is much higher that the dose for an individual substance. According to Coupe et al. (1998), insecticides and herbicides are used up to approx. 5 kg/ha and 7 kg/ha. For EDIPTEX, it has been decided to apply the following substances and volumes in the calculations:
Thus, production of 18 g "pesticides" is required per kg cotton. According to USDA (1999), the insecticide Esfenvalerate was not among the most common ones, but is was used. This insecticide has been selected for EDIPTEX, as it was not possible to obtain enough data for calculation of equivalency factors for the most common insecticides. Energy consumptionAs for energy consumption for cultivation and harvest, it has not been possible to find good data that are newer than those calculated and stated in Van Winkle et al. (1978). In recent times, both Kallila, E. (1997) and Laursen, S.E. et al. (1997) have reviewed literature thoroughly without finding newer and better data. Data from other sources, such as Svensson (1995), are not deemed correct. Van Winkle et al. (1978) states energy consumption of 49 MJ/kg packed raw cotton. This figure includes electricity and fuel for cultivation, harvest and ginning. Moreover, energy for production of fertilizer and pesticides is included in Van Winkle's data. In order to estimate the energy consumption for production of organic cotton however, it was necessary to calculate the energy consumption for production of fertilizer and pesticides in separate processes. In table 1, Van Winkle et al. (1978) state the energy consumption for cultivation and harvest of cotton. Van Winkle states the data in ”kWh equivalents per lb lint cotton”, and the kWh equivalents correspond to ”fossil fuel equivalents”, corresponding to the level called ”primary energy” in the EDIP method. Van Winkle states that consumption of electricity has been multiplied by 3 to convert it to ”fossil fuel equivalents”. Here, these ”fossil fuel equivalents” have been converted in order for them to be applicable in accordance with the EDIP method. In order to be able to calculate the emissions, resource consumption and waste volumes resulting from generation of energy, it has been necessary to estimate how much energy cotton producers recover per kg harvested cotton - calculated as the kWh electricity and kg oil. Van Winkle's data have been converted from lb to kg, and electricity consumption was converted to the recovered amount of electricity by dividing by 3. The remaining energy consumption has been converted to the amounts of energy resources used. The following energy content has been used for the calculation: 53.49 MJ per kg natural gas, 46.4 MJ per kg LP gas, 45.85 MJ per kg diesel oil and 46.89 MJ per kg petrol. With these modifications, Van Winkle's data can be converted to the following: For cultivation and harvest of cotton (excluding energy consumption for production of pesticides and fertilizer) the following is used:
The energy consumption for production of pesticides and fertilizer can be seen in the processes TX-K-05, TX-K-06, TX-K-07 and TX-K-08, and perhaps it should be noted that this energy consumption tallies well with the energy consumption stated by Van Winkle, although much newer references have been applied. Water consumptionThe reality of water consumption is just as complicated as that of chemicals. In some regions, it is not even necessary to irrigate artificially as the region has enough rain. The following calculation has been made: Cotton needs approx. 50 cm water during one growth season - either in the form of rain or irrigation (Lee et al., 1984). This is approx. 5,000 m³ per hectare. In 1992/93, artificial irrigation was only carried out on approx. 43 per cent of areas in the US. The use of irrigation varied a lot in the areas where irrigation was actually used. An average weighting of more than 30 per cent of the total area with total irrigation is therefore not deemed reasonable. For the US, with an average crop of approx. 785 kg/ha in 1992/93, we get an estimate of 5,000 * 0.3/785 = approx. 2 m³ water per kg packed raw cotton. This is the assessed minimum required in the US. Marini (1996) states that the actual water consumption could reach as much as 29 m³ per kg packed raw cotton in some areas of the world. AllocationApprox 2 kg cotton seeds come from each kg cotton produced. Cotton seeds can be used for oil or feed. This means that cotton seeds do not constitute an actual waste product, but what is called a "coproduct" in lifecycle assessment terms. This represents a value for the cotton cultivator, but there is no doubt for the cotton cultivator that cotton is the main product. The financial value of cotton seeds only represents about 20 per cent of the total revenue (Van Winkle et al., 1978). We have therefore decided to allocate the entire environmental burden to the fibre production. Waste volumesThe waste volumes from ginning - mainly plant residues - vary a lot according to harvesting methods. When the cotton is picked by hand, waste is very limited, only about 0.03-0.32 kg/kg raw cotton. There are two methods of mechanical cotton picking: ”Machine-picking” and ”Machine-stripping”. The corresponding waste figures are 0.09-0.42 and 0.95-2.91 kg/kg raw cotton (Lee et al., 1984). In the US, all conventional cotton is picked by machines, and the distribution between the methods was 79 per cent and 21 per cent respectively in 1992/93 (ICAC, 1993). This gives an average of approx. 0.7 kg waste per kg raw cotton. Chemical residues on cotton fibresThe last aspect that requires some consideration is the amount of cultivation chemicals that may cling to the surface of the raw cotton. In theory, these chemicals can (if they occur in sufficiently large amounts) cause problems for occupational health and safety during handling of the raw cotton and environmental problems because they will be washed out during the subsequent wet treatment in connection with textile production. There is very little literature in this area. Henry et al. (1991) studies the problematic use of the defoliation agent arsenic acid. Arsenic acid used to be the most common defoliation agent. In 14 batches of raw cotton, an average of approx. 100 ppm was found with levels ranging from approx. 1 to 325 ppm, but there was significantly more in vegetable waste. The study also showed that the arsenic acid is no longer traceable in the fibres after the cotton is washed during pre-treatment. Analogous studies of wool reach the same conclusion (pesticides are often applied to sheep, primarily to protect them against parasites). After the fibres are washed during the textile wet treatment, there are normally no residues of pesticides in the fibres. Which pesticides are found in raw cotton, and how much? If we assume that the pesticides cling to the fibres, it is not realistic to find traceable amounts of pesticides used in early growth phases of the cotton plant when no fibres have yet been formed or when fibres are protected inside the seed pods. It should therefore be reasonable to assume that there will only be traces of defoliation agents and no other agents. The use of arsenic acid as a defoliation agent has been more or less phased out in the US. At least, the substance does not appear on the most recent list of common agents (USDA, 1999). As there are no studies available, we assume that in the individual worst case chemicals scenarios, there is approx. 0.005 g defoliation agent per kg cotton on the cotton fibres. This volume is passed on to the textile where it is assumed that everything is washed out during pre-treatment. List of references for data for cultivation and harvest of cottonEU, 1998. Establishment of ecological criteria for textile products. Environmental Assessment. Kalliala, E., 1997. The ecology of textiles and textile services. A lifecycle assessment study on best available applications and technologies for hotel textile production and services. Finland. Svensson, E., 1995. Livscykelanalys – Arbetskläder – Inventering. IFP. Sweden. Van Winkle et al., 1978. Cotton versus polyester. American Scientist, Volume 66. ICAC, 1993. Survey of cotton production practices. International Cotton Advisory Committee. Report prepared by the secretariat for the 52nd Plenary Meeting held in New Delhi, India. Laursen, S.E et al., 1997. Environmental assessment of textiles. Environmental Project No. 369. Danish EPA, Denmark. TAS, 1992. The Agrochemical Service. County NatWest and Wood Mac Business Consultancy Unit. Melliand International (2), 1996. Fiber World production 95. June 1996. Dollacker, A., 1996. Rolle des pflanzenschutzes im Baumwollanbau. Melliand Textilberichte 12/96. Coupe, R.H. et al., 1998. Relation of usage to the occurrence of cotton and rice herbicides in three streams of the Mississippi Delta. Environ. Sci. Technol, 32, 3673-3680. USDA, 1999. Agricultural Chemical Usage. 1998 Field Crops Summary. United States Department of Agriculture, May 1999. Lee J.A. et al., 1984. Cotton as a world crop. Agronomy Monograph Series No. 24. Wisconsin, USA. Marini I, et al., 1996. Welche sind die wichtigen Unterschiede zu den anderen cellulosischen Fasern? Lenzing-Lyocell. 17. IFVTCC Kongress, Wien. Henry et al., 1991. Effects of mechanical processing and wet treatments on arsenic acid desiccant residues in cotton. USDA, ARS. Cotton quality Research Station, Clemeson, S.C., USA. Hauschild M: Estimating pesticide emissions for lifecycle assessment of agricultural products. From: B P Weidema and M J G Meeusen (eds.): Agricultural data for lifecycle assessments, LCAnet Food.
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