Soybean is an important feedstock and its oil represents 70% of the raw material used for the production of Brazilian biodiesel. The main purposes of this work was to present a Life Cycle Inventory of soybean produced in Rio Grande do Sul, state in Brazil, based on primary data of agricultural soybean production in this region. Inventory data was collected in 23 municipalities that account for 32% of total soybean production. A Machinery Operation Modeling was suggested to adjust agricultural machinery inputs/outputs for harvesting under study. The soybean cultivation Life Cycle Inventory was divided into four stages and not as a black box. Based on questionnaire responses, it was possible to characterize some regional peculiarities of soybean production. For the estimation of Greenhouse Gas emissions from direct land use change and nitrous oxide emissions from soil, an assessment of soybean advancement over distinguished areas was performed. The results showed that for 15.4% of cultivated area from 1992/93 to 2012/13 transition from pasture to farming has occurred, mainly over rice and corn crops. It should be underscore that no evidence of soybean advances from forest to farming was found for the region. Moreover, this work considered nitrous oxide emissions from soil and a complete inventory was presented. Lastly, this works aims to offer soybean inventory data specifically to Rio Grande do Sul state and presents a new approach to perform environmental results related to agricultural life cycle assessment.