Efficient anaerobic digestion of a mild wet air pretreated molasses ethanol distillery stillage: A comparative approach

Getachew Dagnew Gebreeyessus; Trichur Ramaswamy Sreekrishnan; Andualem Mekonnen; Yonas Chebude; Esayas Alemayehu

doi:10.1016/j.heliyon.2020.e05539

Efficient anaerobic digestion of a mild wet air pretreated molasses ethanol distillery stillage: A comparative approach

Heliyon. 2020 Nov 18;6(11):e05539. doi: 10.1016/j.heliyon.2020.e05539. eCollection 2020 Nov.

Authors

Getachew Dagnew Gebreeyessus^{1

2}, Trichur Ramaswamy Sreekrishnan³, Andualem Mekonnen⁴, Yonas Chebude⁵, Esayas Alemayehu⁶

Affiliations

¹ Africa Center of Excellence for Water Management, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia.
² Department of UEM, Kotebe Metropolitan University, P.O. Box 31248, Addis Ababa, Ethiopia.
³ Department of Biochemical Engineering and Biotechnology, IIT Delhi, India.
⁴ Center for Environmental Sciences, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia.
⁵ Department of Chemistry, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia.
⁶ Jimma Institute of Technology, Jimma University, P.O. Box 378, Jimma, Ethiopia.

Abstract

The effect of a mild, wet air pretreatment and the subsequent anaerobic digestion (AD) was examined on the recovery of a complex and toxic molasses ethanol distillery stillage. The biogas yield and organics removal due to pretreatment were compared with the raw stillage AD. The application of a scoria support in this industrial residue AD process stability was also assessed. Consequently, a statistically significant cumulative specific methane recovery difference (p-value = 0.000) with an almost complete biological oxygen demand (BOD) removal and a significant chemical oxygen demand (COD) reduction, which were 100% and 92% respectively were achieved. Additionally, the biogas recovery rate was hastened due to pretreatment. The application of scoria, whose property has been instrumentally inspected, has helped stabilize the pH in the AD systems. In a comparative approach, this study suggests the energy benefit and an ecofriendly discharge of stillage by the ethanol industry towards sustainability.

Keywords: Bioengineering; Biogas; Chemical engineering; Chemical oxygen demand; Environmental engineering; Environmental hazard; Environmental health; Environmental management; Environmental pollution; Environmental risk assessment; Environmental science; Environmental toxicology; Scoria; Stillage; Wet air pretreatment.