Comparison of mesophilic and thermophilic anaerobic digestion of sugar beet pulp: Performance, dewaterability and foam control

Abstract

Digestion of sugar beet pulp was assessed in relation to biogas and methane production, foaming potential, and digestate dewaterability. Four 4-litre working volume digesters were operated mesophilically (37 ±0.5 o C) and four thermophilically (55±0.5 o C) over three hydraulic retention times. Digesters were operated in duplicate at organic loading rates (OLR) of 4 and 5 g volatile solids l -1 day -1 without water addition. Thermophilic digestion gave higher biogas and methane productivity than mesophilic and was able to operate at the higher OLR, where mesophilic digestion showed signs of instability. Digestate dewaterability was assessed using capillary suction time and frozen image centrifugation. The occurrence of, or potential for, stable foam formation was assessed using a foaming potential test. Thermophilic operation allowed higher loadings to be applied without loss of performance, and gave a digestate with superior dewatering characteristics and very little foaming potential.

Enhanced mesophilic anaerobic digestion of food waste by thermal pretreatment: Substrate versus digestate heating

“…Theoretically, thermophilic AD (TherAD) is preferred over mesophilic AD (MesAD), as recent studies have shown that: (i) TherAD is kinetically favoured over MesAD, thus resulting in a shorter retention time and poses a higher possibility to increase the organic loading rate (El Mashad et al, 1994;Angelidaki et al, 2006;Esposito et al, 2011), (ii) TherAD has a higher rate of organic matter degradation with a higher biomethane production (Gavala et al, 2003;Labatut et al, 2014;Suhartini et al, 2014), and (iii) TherAD holds a better potential to inactivate pathogens, thus complying with the EU policy for elimination of pathogens as well as obtaining Class A biosolids according to the USEPA guidelines (Labatut et al, 2014;Suhartini et al, 2014;Wagner et al, 2008;Ziemba and Peccia, 2011).…”

Effects of thermal pretreatment on acidification phase during two-phase batch anaerobic digestion of kitchen waste

“…Two-phase AD may offer an attractive alternative to conventional one-phase anaerobic digestion because it has several advantages over traditional single-phase systems [13,41], such as a considerably shorter detention time [8,16], higher gas conversion efficiency [6,15,21] and higher methane concentration [37,6], either under mesophilic or thermophilic conditions [20]. This process has been researched in numerous fields, including those associated with waste water [24], fruits and vegetables [31], sewage sludge [7,35].…”

Foam formation in full-scale biogas plants processing biogenic waste

“…Furthermore, the presence of specific substances such as protein [14], fat, oil, and grease [11] as well as suspended particles [6] was found to contribute to foam formation during the AD. Also, the AD of some substrates such as sugar beet pulp [16,17], acidic whey in connection with chicken manure [14], and slaughterhouse waste [18] is accompanied by enhanced foam formation. Kougias et al [14] reported that onefifth of the interviewed biogas plant operators could not identify the real causes of foaming in their digester.…”