Alternative wood preservation in rural areas: comparative evaluation between vegetable and mineral oils

This study evaluated the efficiency of reused soybean vegetable oil and waste mineral lubricating oil, applied both cold and hot, for the preservation of Pinus sp. stakes exposed in a field decay test. A total of 160 wood samples were distributed among five treatments and two environmental conditions and monitored for 400 days. Variables such as preservative absorption, mass loss, and visual deterioration index were analyzed. The heated soybean vegetable oil (150°C) exhibited the best performance, showing higher absorption, lower mass loss, and improved visual appearance. Statistical analysis revealed a significant difference among treatments (H = 18.73; p = 0.0009) and a strong negative correlation between preservative absorption and mass loss (ρ = –1.0; p < 0.001). A similarly strong correlation was observed between visual rating and mass loss (ρ = –0.83; p < 0.001), confirming the reliability of the visual assessment. It is concluded that the use of recycled vegetable oil, particularly when applied hot, represents a sustainable, low-cost, and technically viable alternative for wood preservation in rural environments.