Micronised keratinous wastes as co-substrates, and source of nutrients and microorganisms for trichoremediation of petroleum hydrocarbon polluted soil

Micronised keratinous wastes consisting of human hairs and chicken feathers were used as co-substrates and sources of nutrients and microorganisms for trichoremediation of used engine oil-polluted soil. The effects of biostimulation and co-metabolic degradation of the substrates by naturally associated microorganisms were monitored for 180 days. The microbial activities, growth, interactions and diversity were investigated for the total petroleum hydrocarbons (TPHs). The results showed a higher removal of TPH with micronised keratinous wastes than in the bioattenuation in the controls. Micronised keratinous wastes served as bio-stimulatory agents, bulking materials, bio-carriers, microbial agents, soil conditioners and slow-release fertilisers. The results showed TPH removal (74.51%, 91.54% and 86.57%) in the presence of micronised hairs, feathers and admixture of hairs and feathers, respectively, while bioattenuation in the live and killed controls recorded TPH removal (22.51%) and (18.53%), respectively. The microbial growth kinetics and microbial community diversity were improved. The principal component analysis (PCoA) indicated that the microbial communities in the treated soil were distinct and significantly different from the control without keratinous wastes. The utilisation of micronised keratinous wastes for soil remediation offers an excellent environmental-friendly, cost-efficient, sustainable, and feasible way of restoring petroleum hydrocarbon polluted soil for land use while simultaneously managing the abundance of the keratinous wastes in the environment.