Reducing carbon emissions from soybean cultivation to oil production in Thailand

The purpose of this study was to evaluate the carbon equivalences (CE) of whole-chain soybean oil production, starting from plantation until production of soybean oil. Appropriate approaches for the reduction of carbon emissions were also evaluated. Following a carbon-balanced model, total carbon emissions from soybean oil production were found to be +711 ± 14 kg CE/ton soybean oil. Cultivation, threshing, and industrial phases were responsible for 63%, 3%, and 34% of overall emissions, respectively. The highest equivalent carbon emissions in the cultivation process come from use of diesel fuel for watering and spraying chemical fertilizers. Meanwhile, the most significant emission from soybean oil production was found to be due to fuel oil used for steam production, contributing to 52% of total emissions in industrial phase. In addition, emissions from soybean meal, a co-product from soybean oil industry is equal to 169 kg CE/ton soybean meal. It involves fixed carbon as valuable protein sources sent to feed mills. From the complete carbon cycle scenarios of soybean oil production, the carbon fixation efficiency is computed to be equal to 74.7%. This indicates that soybean oil production still continues to emit carbon into the atmosphere. However, nutrients fixed in plant residues remaining in cultivation areas help reduce carbon emissions of about 175 ± 23.8 kg CE/ha from decreasing amount chemical fertilizers to be applied. From the selected scenarios, potential reductions of carbon emissions from soybean oil production were found to be 87% as compared to existing conditions. Moreover, cost saving from selected approaches to reduction of carbon emissions were estimated to be 7.4 Baht/kg soybean oil (0.21 USD/kg soybean oil). Based on emitted CE, the unit cost of soybean oil production was found to be 49.6 Baht/kg CE (1.41 USD/kg CE).