Greenhouse gas assessment of Brazilian soybean production: a case study of Mato Grosso State

In recent years, the debate about environmental impacts and the sustainability of agricultural products has increased. Environmental impact indicators are increasingly being demanded for policy and decision-making processes. Consumers are more and more concerned about the quality of food products and now looking for those with a low environmental impact, with a particular attention to greenhouse gas (GHG) emissions. There are few studies regarding the GHG emissions associated with the Brazilian soybean production. The aim of this study was to evaluate the main sources of GHG in soybean production in the State of Mato Grosso, Brazil. Our analysis considered the Life Cycle Assessment (LCA) from cradle to farm gate. We evaluated 55 farms in the crop years of 2007/08, 2008/09 and 2009/10, accounting for 180,000 ha of soybean cultivation area and totaling 114 individual situations. The results indicated that the largest source of GHG in the soybean production is the decomposition of crop residues (36%), followed by fuel use (19%), fertilizer application (16%), liming (13%), pesticides (7%), seeds (8%) and electricity consumed at the farms (<1%). The average GHG emissions considering the three crop years were 0.186 kg of CO(2)eq kg(-1) of soybean produced. We also categorized the results based on land use intensity and production areas. This study contributed to identify the main sources of GHG in the soybean production and indicate mitigation priorities associated to the soybean cultivation in Brazil. Further studies, including field experiments, should contribute to a better understanding of the profile of emissions from crop residues in Brazil. (C) 2014 Elsevier Ltd. All rights reserved.