Modelling pesticide emission patterns in agricultural life cycle inventories using a modular approach: Case study of apple production in New Zealand

In the Life Cycle Assessment (LCA) of field crops, the system description and inventory analysis provides information about the identities and quantities of pesticide applied, the form and the pattern of application. The field itself is seen as part of the technosphere, the ecosphere beginning outside the boundaries of the field or below the ploughing zone. To determine emissions of pesticide ingredients, we need to model their fate in the field system in order to quantify the fractions which cross its boundaries entering into the ecosphere. A modular framework for the calculation of organic pesticide fractions reaching the different environment compartments is used for the application of LCA to apple production in New Zealand. The approach has been developed to be used in the life cycle inventory (LCI) of agricultural systems. This framework allows the consideration of site-dependent parameters and farmers, habits in the calculation procedure, and is therefore very useful to increase the sophistication of agricultural LCA. The approach requires few parameters of the pesticides (Koc, vapour pressure, half-lives in soil and on the plant), and of the site (soil type and rainfall), and its modularity allows to include more sophistication in the different modules as required. For instance, in New Zealand a complex mechanistic model exists for the prediction of pesticide leaching, as well as field data on farmers' habits' effect on pesticide drift, so this was included in the calculations. The effect of pesticide parameters, site conditions and farmers' habits on the pesticide emission patterns has been described for some pesticides. The feasibility and practicality of the model is discussed in relation to other, more complex, models.