Abstract
Gelatin production is the most industry polluting process where huge amounts of raw organic materials and chemicals (HCl, NaOH, Ca2+) are utilized in the manufacturing accompanied by voluminous quantities of end-pipe effluent. The gelatinous wastewater (GWW) contains a large fraction of protein and lipids with biodegradability (BOD/COD ratio) exceeding 0.6. Thus, it represents a promising low-cost substrate for the generation of biofuels, i.e., H2 and CH4, by the anaerobic digestion process. This review comprehensively describes the anaerobic technologies employed for simultaneous treatment and energy recovery from GWW. The emphasis was afforded on factors affecting the biofuels productivity from anaerobic digestion of GWW, i.e., protein concentration, organic loading rate (OLR), hydraulic retention time (HRT), the substrate to inoculum (S0/X0) ratio, type of mixed culture anaerobes, carbohydrates concentration, volatile fatty acids (VFAs), ammonia and alkalinity/VFA ratio, and reactor configurations. Economic values and future perspectives that require more attention are also outlined to facilitate further advancement and achieve practicality in this domain.
Highlights
Magnetite/graphene oxide (MGO) nano–composite (100 mg/L) was successfully utilized to increase the hydrogen yield and productivity; i.e., 112.4 ± 10.5 mL H2 /gCODremoved from gelatinous wastewater by immobilization on the anaerobes [6]
Fang and Yu [32] found that gelatin degradation decreased from 65.2 to 51.9% with the increase in influent gelatin concentration from 2 g/L to 30 g/L due to the growth retardation of C. collagenovoransa at 100 mM acetate in the fermentation medium
The gelatinous wastewater is rich in protein which can be biodegraded by anaerobic bacteria for energy recovery in terms of H2 and CH4
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Each ton of raw materials, mainly bones, produces 300 m3 of gelatinous wastewater [2]. The GWW could be alkaline or acidic based on the manufacturing process and the utilized raw materials [9]. GWW is greasy and fibrous containing bovine bone pieces and hairs, resulting in high quantities of particulate organic matters [11,12]. Energies 2021, 14, 4936 acidic based on the manufacturing process and the utilized raw materials [9]. 9691.2 to 23,016 mg/L due The to the usagehide of raw materials rich tank in proteins, and12.0 for 1 weeks, resulting in high residual values of calcium in the wastewater ran carbohydrates. 10–12 weeks, resulting in high residual values of calcium in the wastewater streams ranging the manufacturing process resulting in alkalinity of.
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