O presente estudo foi realizado com o objetivo de se avaliar diferentes métodos para o cálculo de graus-dia (GD). Foram comparados quatro métodos de soma térmica, frequentemente usados no cálculo de GD: Ometto, Snyder, Dufault e método residual de Arnold. Esses métodos foram aplicados às culturas do milho e do feijão. As simulações foram feitas com as temperaturas observadas em Viçosa, MG no ano de 2011, e temperaturas simuladas (com acréscimo aleatório entre 0 a 5ºC em cada dia do período). As respostas dos quatro métodos de cálculo dos GD foram similares para as temperaturas observadas (reais). Para as temperaturas elevadas, os métodosnão apresentaram respostas similares. Fixando os graus-dia em 1.600 ºC dia para a cultura do milho e 1.300 ºC dia para o feijão, os métodos estudados reduziram de forma diferente o ciclo das culturas. As maiores reduções foram obtidas pelo método Arnold e Snyder, reduzindo igualmente o ciclo em 28 e 17 dias para as culturas do milho e do feijão, respectivamente. No método de Ometto, foram observadas as menores reduções, de 12 (milho) e 11 (feijão) dias, pois, nesse caso utilizam-se as temperaturas basais superior e inferior e considera-se uma penalização maior em dias em que a temperatura máxima ultrapassa a temperatura basal.

The production of dairy products generates several environmental impacts, and life cycle assessment (LCA) is a useful methodology to quantify and understand those impacts. In Brazil, some traditional dairy products have not yet been evaluated using the LCA methodology. Based on this gap, we conducted a cradle-to-gate LCA of six dairy products from a plant in Minas Gerais, Brazil. We also performed two sensitivity analyses. The first analysis was on how the environmental profiles of the products changed depending on how the multifunctional processes were allocated. The second analysis evaluated how these changes in environmental profiles occurred depending on the way that the impacts were allocated to products and by-products (whey and buttermilk) produced within the dairy factory. Among the dairy products studied, the impacts of mozzarella cheese and butter substantially surpassed those of other products; cheese spread and dulce de leche had a similar impact; and yoghurt and milk had the lowest values for the impact categories that were assessed. The inclusion of by-products in the analysis proved to be an effective way to reduce the environmental impacts attributed to the dairy products, especially for cheese and cheese spread, the impact values of which decreased by 56% and 46%, respectively. Additionally, the use of different strategies to deal with the multifunctional processes significantly affected the impact results of the dairy products. The subdivision of processes combined with causal allocation was the best alternative as opposed to the allocation by milk solids. These results could offer a better understanding of the environmental profiles of dairy products from Brazil, especially the traditional products, such as dulce de leche and cheese spread. Other contributions of this study include the proposal of alternatives that could improve the environmental profiles of products (such as the processing of by-products and the questioning of the use of allocation according to milk solids, which have been commonly used in other life cycle assessment studies) and the proposal of a better method for assessing the environmental impacts of dairy products.