Alkaline And Thermal Inocula Pretreatments in Cheese Whey Anaerobic Digestion on Apparent Kinetics Parameters and Volatile Fatty Acids and Biogas Production

Cheese whey is a by-product of the dairy industry containing high organic load (50-60 g COD L-1). Although food and pharmaceutical industries technologies are able to recover this by-product into added-valueproducts, about 41.4% is still used as fertilizer, animal feed or discarded in water bodies. Anaerobic digestion (AD) is an effective process for repurposing this share into volatile fatty acids (VFA) or biogas. This work studied the variables involved in the anaerobic digestion of cheese whey for both organic matter removal and biogas and volatile fatty acids production. The study used alkaline (at pH 8.0) and thermal (at 90 °C) pretreatments followed by initial pH corrections of 7 and 9. Carbohydrate rate consumption showed an average efficiency of 96%. This demonstrated that hydrolysis was not the limiting step in this anaerobic digestion. Thermal pre-treated inoculum with higher initial pH (T9) presented a more efficient organic matter removal (35%). Reactor T7 presented the most VFAs production with an accumulated production of 1,716 mg VFAs L-1. The present work can lead to the refinement of pre-treatment parameters for VFAs production using cheese whey as substrate, repurposing this largely available raw material from the dairy industry into more added-value products.