Study of the bioremediation potential of vegetable oils in cerrado soils of maranhão through natural attenuation (passive bioremediation)

In Brazil, the annual production of approximately three billion liters of edible vegetable oil yields only 2.5% of used cooking oil for reuse, while the remainder is improperly discarded, resulting in significant environmental impacts. This impact includes soil and water contamination, affecting both fauna and flora. Residual vegetable oil (RVO), whether virgin or used, has adverse effects, including soil impermeabilization and groundwater contamination, and may even release greenhouse gases such as methane. A treatment and a control were applied, each with three replicates, using residual vegetable oil (RVO). In each hermetically sealed container, 500 g of soil was artificially contaminated with 12.5 mL of RVO. Additionally, an open container with 20 mL of 0.40 mol L⁻¹ NaOH solution was placed above the contaminated soil to capture CO₂ produced during remediation. CO₂ capture assessments were conducted at 20, 40, 60, and 80 days of incubation. Given the natural slowness of soil regeneration, it is vital to employ remediation techniques, with passive bioremediation being a commonly used approach. In this context, the present study aims to evaluate the passive bioremediation technique through in vitro tests as a method to remediate soils from the Cerrado region of Maranhão artificially contaminated with residual soybean oil (RVO). The passive bioremediation technique proved to be an effective option for degrading residual vegetable oil. Under the conditions investigated, CO₂ production over time was highest at 80 days in site 1, while in site 2 the highest production occurred at 60 days. Therefore, it can be concluded that the passive bioremediation technique can be applied to the Cerrado soils of Maranhão.