Pre-treatment of distillery spent wash (vinasse) with vortex based cavitation and its influence on biogas generation

Abstract

Distilleries generate high COD (chemical oxygen demand) wastewater streams that are anaerobically digested to produce biogas with sub-optimal yields. In this work, for the first time, novel vortex-based hydrodynamic cavitation (HC) pre-treatment of these waste streams was investigated for significantly enhancing biogas yields. Molasses spent wash (120,000 ppm COD, India) and vinasse (27,000 ppm COD, Brazil) were pretreated at varying number of passes (between 1 -20) through the HC device at constant inflow, biochemical methanation potential (BMP) was measured and described using a first order model. Vortex-based HC pre-treatment led to 14% enhancement (2 passes) in BMP from spent wash (difficult to digest compared to vinasse) with a net energy gain of 1 GJ/ton COD. 10-22% increase in biogas yields from large-scale industrial spent wash digesters confirmed the laboratory findings. The work presented is useful and can be translated to recalcitrant feedstock for enhancing valorization using vortex-based HC pre-treatment.

Sugarcane bagasse based biorefineries in India: potential and challenges

“…Physicochemical pre-treatment seems a promising method in terms of scalability and energy efficiency, not only for saccharification or bioethanol production but also for enhancing biogas yields via anaerobic digestion (AD) of SCB. For instance, the use of hydrodynamic cavitation (HC) as a biomass pre-treatment method is increasing rapidly 41,52,53 . HC is the phenomenon of formation, growth and implosion of vaporous cavities.…”

Valorizing Waste Biomass via Hydrodynamic Cavitation and Anaerobic Digestion

“…The extent of enhancement in BMP obviously depends on the nature of the feedstock as well as extent of pretreatment. For example, Nagarajan and Ranade 89 reported a 14% enhancement in BMP by pretreating distillery spent wash using a vortex-based HC device.…”

“…Vortex-based devices have been scaled up 120 systematically and have also been applied successfully for industrial AD intensification applications. 89 For instance, Simpson et al 104 studied the hydrodynamics of linear and swirl flow devices using computational fluid dynamic (CFD) models. Detailed experimental investigations of the flow behavior in these devices using high-speed photography was also conducted to validate the results of the CFD model.…”

“…These fitted parameters obtained via nonlinear regression analysis were able to describe the gas generation from the untreated and HC pretreated feedstock sufficiently. Nagarajan and Ranade 89 also used an additive first order model to describe gas generation from distillery spent wash that exhibited diauxic digestion. Stromberg et al 134 investigated the use of six different empirical models to predict lab scale BMP earlier before completion.…”

ANN based modelling of hydrodynamic cavitation processes: Biomass pre-treatment and wastewater treatment

“… [5] , [26] , [33] , [24] . Combination of intense shear and hydroxyl radicals have also been harnessed for a range of physico-chemical processes such as pre-treatment of waste biomass [11] , [3] , [18] , [19] ). HC is therefore touted as a very promising platform [9] , [13] , [17] .…”