Optimisation of anaerobic digestion of pot ale after thermochemical pre-treatment through Response Surface Methodology

Abstract

Valorisation of organic wastes in renewable energy production has attracted a global attention in order to achieve a sustainable industrial growth. Anaerobic digestion (AD) is considered to be one of the most environmentally friendly waste management technology and also fulfils the necessity of a sustainable fuel generation. It has much less energy demand than other technologies like gasification or pyrolysis due to its low operation temperature. Whiskey distillery wastewater, pot ale, is classified as a high strength waste due its high organic content hence rendering it a suitable substrate for anaerobic digestion. Despite its waste-to-energy conversion potential, pot ale contains high lignin fraction which makes it resistant to biodegradation. Therefore introducing a pre-treatment step is required to enhance the biogas production and organic matter degradation. In this study anaerobic digestion of pot ale was assessed at lab scale batch mode reactor after implementation of 1 M NaOH and microwave pre-treatments at varying power settings. Response Surface Methodology was adopted for process modelling and optimisation in which inoculum substrate ratio, initial digestion pH and microwave power were investigated at three different levels. In addition, the mineral quality of the pot ale digestate has been analysed for its agricultural use.