Title : A Novel approach using household waste digestate to overcome mono-ethylene glycol inhibition for hydrogen producers
Abstract:
Oily sludge (OS) is a hazardous by-product of petroleum exploitation processes, rich in petroleum hydrocarbons such as mono-ethylene glycol (MEG). This hazardous waste poses significant environmental concerns and reduces opportunities for further utilization, such as bioenergy and biochar. Traditional physicochemical treatments of OS are commonly employed; however, they often result in the harmful disposal of hazardous solids into the environment. One common method is land treatment, where OS is mixed with soil and placed carefully in the ground layer. Nevertheless, this approach requires a large surface area for OS burial, making it a time-consuming and uncontrollable process. Further, it can lead to the release of volatile pollutants rich in toxicants, phenols, and hydrocarbons in the leachates. Composting of OS is of great interest as an alternative treatment technology that eliminates toxic compounds, but it is known for its time and energy-consuming process, and poor treatment capacity. Microbial biodegradation is a promising treatment process for reducing the hazardousness of OS to the environment and human health. Pretreatment of OS is preferable to solubilize and facilitate the biodegradation process. Herein, a novel approach for H2 production is presented by exploiting the synergistic potential of digestate derived from household waste (D) in the co-digestion process with oily sludge (OS), rich in mono-ethylene glycol (MEG). Our approach significantly mitigates the environmental impact of OS, a hazardous byproduct of petroleum industry, while addressing the challenge of MEG inhibition in H2 production, along with biochar recovery. Remarkably, anaerobic co-digestion of OS:D (60:40) yielded a remarkable 23.1-fold increase in hydrogen potential (436.3±34.8 mL) compared to 18.7±0.9 mL in OS:D (100:0). This enhanced hydrogen productivity was complemented by a notable MEG biodegradation efficiency of 86.2±7.8%. Furthermore, the microbial community played a crucial role in metabolizing MEG into ethanol, acetaldehyde, and acetate through the enzymatic activities of aldehyde dehydrogenase and alcohol dehydrogenase. Dominant strains such as Clostridium (3.9%), Acinetobacter (12.7%), and Bacillus (2.1%) were identified for MEG degradation, contributing significantly to high H2-productivity.
