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.

Spent Grain from Malt Whisky: Assessment of the Phenolic Compounds

“…Whisky is one of the most popular alcoholic beverages made from cereals, and generally are all produced in a similar manner [ 1 , 2 ]. Today, whisky is drunk in over 200 countries around the world, making it one of the most consumed alcoholic beverages globally [ 3 , 4 ]. Whisky consumption per capita varies by country, with France at the top by about 2 L per person per year, while India is the country with the highest total consumption [ 5 ].…”

“…The high humidity content of 74–80% of this by-product gives it a short shelf life; being prone to microbial contamination, it has limited use and is not suitable for long-distance transport [ 14 ]. Spent grain contains peel, pericarp, and seeds with high cellulose levels (16.8–25.4%), hemicellulose (mainly arabinoxylans) (21.8–28.4%), lignin (11.9–27.8%), protein (20–25%), or fibers [ 4 , 10 ]. Most of the weight of spent grain is water, distributed during the mashing process.…”

Characteristics of Biogas Production from Organic Wastes Mixed at Optimal Ratios in an Anaerobic Co-Digestion Reactor

“…Based on the derived results, multiple linearity and variance analyses were performed [23]. The status of organic waste degradation and an appropriate mixing ratio for the stable operation was determined using Design Expert 10, as summarized in Table 5 [24].…”

Potassium Hydroxyde Pre-Treatment Enhances Methane Yield from Giant Reed (Arundo donax L.)

“…The biogas produced through anaerobic digestion (AD) is one of the biofuels on which most attention is focused. Anaerobic digestion is considered an environmentally friendly fuel generation technology as it requires a lower energy input than that required for the production of other biofuels [1,2]. Besides, the AD process can rely on the utilization of residual biomass, by-products, or waste.…”

“…Among chemical pre-treatments, alkaline pre-treatments increase the porosity of lignocellulosic materials, dissolving lignin through the solvation and saponification of the ester bonds between lignin and holocellulose, releasing the structural carbohydrates and making them available for AD [9]. The thermal pre-treatment of lignocellulosic biomass has been extensively studied [1]. The combination of thermal and alkali pretreatments can increase biomass degradation, however, thermo-alkaline pre-treatments can generate microbial inhibitors, such as polyphenols resulting from the degradation of lignin [7,10,11], dissolved in a salty alkaline solution.…”