Compost humic acid-like isolates from composting process as bio-based surfactant: Properties and feasibility to solubilize hydrocarbon from crude oil contaminated soil

Biodecomposition of organic solid waste during composting process produces compost humic acid-like (cHAL), which is classified as biobased surfactant. The present study aimed to characterize the properties of cHAL substance which was formed during the composting process of crude oil contaminated soil, in terms of surface tension decline (ΔST) and emulsification activity (EA), and evaluate the ability to solubilize hydrocarbons. Crude oil contaminated soil from a public oilfield in Wonocolo Sub-district, Bojonegoro, Indonesia, was composted under aerobic condition with varied biodegradable waste (yard waste and rumen residue) in separate reactors. The cHAL compounds were isolated from composting products from yard waste (Y₁₀₀), rumen residue (R₁₀₀), control of contaminated soil (S₁₀₀), and mixed of contaminated soil and biodegradable waste (S₅₀YR₅₀). The results showed that ΔST of cHAL isolates were ranged from 6.65 to 21.50 mN/m. The EA of cHAL isolates were in the range of 7.35–38.01%. The cHAL isolates were capable to solubilize 99 to 10,710 μg/g of hydrocarbons. The cHAL isolates from R₁₀₀ and S₅₀YR₅₀ are potential as surface tension reducer and emulsifier for hydrocarbon with values of those isolates were close to 0.50% Tween 80 characteristics, and the abilities to solubilize hydrocarbon were comparable to 1.00% Tween 80. A composition of 50% crude oil contaminated soil and 50% of biodegradable waste (yard waste and rumen residue) is recommended for composting crude oil contaminated soil.