Abstract
Soybean biodiesel (B100) has been playing an important role in Brazilian energy matrix towards the national bio-based economy. Greenhouse gas (GHG) emissions is the most widely used indicator for assessing the environmental sustainability of biodiesels and received particular attention among decision makers in business and politics, as well as consumers. Former studies have been mainly focused on the GHG emissions from the soybean cultivation, excluding other stages of the biodiesel production. Here, we present a holistic view of the total GHG emissions in four life cycle stages for soybean biodiesel. The aim of this study was to assess the GHG emissions of Brazilian soybean biodiesel production system with an integrated life cycle approach of four stages: agriculture, extraction, production and distribution. Allocation of mass and energy was applied and special attention was paid to the integrated and non-integrated industrial production chain. The results indicated that the largest source of GHG emissions, among four life cycle stages, is the agricultural stage (42–51%) for B100 produced in integrated systems and the production stage (46–52%) for B100 produced in non-integrated systems. Integration of industrial units resulted in significant reduction in life cycle GHG emissions. Without the consideration of LUC and assuming biogenic CO2 emissions is carbon neutral in our study, the calculated life cycle GHG emissions for domestic soybean biodiesel varied from 23.1 to 25.8 gCO2eq. MJ-1 B100 and those for soybean biodiesel exported to EU ranged from 26.5 to 29.2 gCO2eq. MJ-1 B100, which represent reductions by 65% up to 72% (depending on the delivery route) of GHG emissions compared with the EU benchmark for diesel fuel. Our findings from a life cycle perspective contributed to identify the major GHG sources in Brazilian soybean biodiesel production system and they can be used to guide mitigation priority for policy and decision-making. Projected scenarios in this study would be taken as references for accounting the environmental sustainability of soybean biodiesel within a domestic and global level.
Highlights
Environmental sustainability has been a major concern of bioenergy industry in the last decade and a number of indicators have progressively emerged in scientific literature [1,2,3,4,5]
Greenhouse gas emission values found in this study fell within a range consistent to other studies that used similar scope and boundaries in this stage [9, 34, 36, 45, 47, 48]
This paper presents the life cycle Greenhouse gas (GHG) emission assessment of soybean biodiesel from the largest Brazilian soybean-producing region to four different destinations (MT-Paulınia Refinary (PA), Mato Grosso (MT)-Port of Santos (PS), MT-PP, MT-EU)
Summary
Environmental sustainability has been a major concern of bioenergy industry in the last decade and a number of indicators have progressively emerged in scientific literature [1,2,3,4,5]. Greenhouse gas (GHG) emission is one of the primary indicators associated to global climate changes and plays a key role within various sustainability analysis approaches [6,7]. The United Nations (UN) and several regional authorities have set sustainability criteria regarding GHG emissions for energy sources and biodiesel is one of the major subjected products [8,9,10]. To meet the growing global demand of biofuels, biodiesel has been an emerging alternative to fossil diesel fuel to guarantee environmental sustainability, especially in Brazil [11]. About 23% of the biodiesel processed in Brazil has been exported mainly to Europe and the Brazilian soybean-derived biodiesel prevails vastly in Spain, France, Italy and Portugal [16, 17]
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