Abstract
Fat waste discarded from butcheries was used as a cosubstrate in the anaerobic codigestion of sewage sludge (SS). The process was evaluated under mesophilic and thermophilic conditions. The codigestion was successfully attained despite some inhibitory stages initially present that had their origin in the accumulation of volatile fatty acids (VFA) and adsorption of long-chain fatty acids (LCFA). The addition of a fat waste improved digestion stability and increased biogas yields thanks to the higher organic loading rate (OLR) applied to the reactors. However, thermophilic digestion was characterized by an effluent of poor quality and high VFA content. Results from spectroscopic analysis suggested the adsorption of lipid components onto the anaerobic biomass, thus disturbing the complete degradation of substrate during the treatment. The formation of fatty aggregates in the thermophilic reactor prevented process failure by avoiding the exposure of biomass to the toxic effect of high LCFA concentrations.
Highlights
Environmental concerns and stringent regulations regarding sludge management and disposal have made it necessary to seek alternatives and feasible solutions for the treatment of such waste
Results of methane yield and volatile fatty acids (VFA) obtained from batch digestion experiments of sludge and codigestion with animal fat at mesophilic and thermophilic conditions are presented in Fig 1A and 1B
VFA produced during the acidogenesis phase accumulated in the system and probably caused an inhibitory stage of acetoclastic methanogenic activity
Summary
Environmental concerns and stringent regulations regarding sludge management and disposal have made it necessary to seek alternatives and feasible solutions for the treatment of such waste. Food-processing industries generate wastewaters and solid fatty byproducts, which are difficult to treat and can cause environmental problems when improperly disposed. Lipid-rich materials, which are abundant in food-processing industries, are known to have high biogas potential. This characteristic makes them an interesting cosubstrate for treatment in anaerobic reactors [1, 2]. In the case of butcheries, due to changes in customer perception of a healthy diet, the amount of animal fat discarded suitable for human consumption is increasing. The valorization of butcher’s animal fat for biogas production will aid in increasing green
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