Avaliação de ciclo de vida da soja mato-grossense

Abstract

A life cycle assessment (LCA) allows a holistic view of a production system. A LCA can identify hotspots along the production chain which can help improve sustainability. The great difficulty in performing an LCA of an agricultural product of a large region is to obtain reliable data that actually represent the average production of the region. This work is a LCA of Mato Grosso soybean where the majority if the information are from primary sources, directly from the producers. The goal is to identify hotspots where improvement efforts would bring greater returns and establish a benchmark to which future LCAs could be compared within a continuous monitoring of the evolution of sustainability. It is a cradle to gate LCA with the average inputs and outputs from 2008 to 2012 to characterize the year 2010, the functional unit was 1 kg of soybean. The production of second crop (safrinha) maize was considered as a co-production of soybeans, a system expansion was done to avoid arbitrariness in the allocation of common inputs. The main source of information was APROSOJA database with information from the production system of 110 farms. Information regarding agriculture operations was obtained from IMEA. From 2000 to 2010 land use change (LUC) was estimated using information from studies based on satellite imaging. Due to lack of information from 1990 to 2000 LUC was assumed to have the same trend as from 2000 to 2010. To produce 1 kg of soybean the occupation of 1.64 m2/year was necessary of which 6.5% came from savannah and 9.1% from forest. This LUC, especially from forest, was largely responsible for much of the impact, particularly the emission of greenhouse gases (1.77 kg CO2eq/kg soybean) and the formation of particulate matter. Phosphate fertilizers, equivalent to 80.7 kg/ha of P2O5 had great impacts in the industrialization phase contributing to the freshwater eutrophication, and during cultivation with the emission of cadmium causing human toxicity. Pesticides were largely responsible for terrestrial ecotoxicity, particularly the fungicide Carbendazim and Azoxzstrobin and the herbicide Atrazine. The second-crop corn generally had lower impact than corn produced in other parts of the world as it used many of the soybean inputs. Nitrogen fertilization of corn is the main source of impact both during the fertilizer production as well as during cultivation. For every kg of soybean 462 g of corn were coproduced, replacing the same amount of corn in the global market. With the system expansion including the production of soybeans and corn the impact of soybean production reduces significantly, even with some negative impacts in some categories. Transformation of natural areas, human toxicity and GHG emissions are the major soybean production impacts. Reduction of forest clearing and phosphate fertilizer as well as an increase in the area planted with second crop maize would have a major impact on reducing the environmental impacts generated by soybean production in MT.